HIGHWAY R E S E A R C H B O A R D

Special Report 68

CONSTRUCTION AND MAINTENANCE EQUIPMENT

A Compilation of Data on Time Utilization, Performance, and Costs

National Academy off Sciences-

National Research Council m

MM'. publication 959

HIGHWAY RESEARCH BOARD Officers and Members of the Executive Committee

1962

OFFICERS R. R. B A R T E L S M E Y E R , Chairman C. D. CuRTiss, First Vice Chairman

W I L B U R S . S M I T H , Second Vice Chairman

F R E D B U R G G R A F , Director W I L L I A M N . C A R E Y , J R . , Assistant Director

Executive Committee RBiX M . W H I T T O N , Federal Highway Administrator, Bureau of Public Roads (ex officio) A . E . J O H N S O N , Executive Secretary, American Association of State Highway Officials

(ex officio) L O U I S JORDAN, Executive Secretary, Division of Engineering and Industrial Research,

National Research Council (ex officio) P Y K E J O H N S O N , Retired (ex officio, Past Chairman 1960) W . A . B U G G E , Director of Highways, Washington Department of Highways (ex officio.

Past Chairman 1961) R. R . B A B T E L S M E Y E R , Chief Highway Engineer, Illinois Division of Highways E . W . B A U M A N , Director, National Slag Association, Washington, D. C. DONALD S . B E R R Y , Professor of Civil Engineering, Northwestern University MASON A . B U T C H E R , County Manager, Montgomery County, Md. J . DOUGLAS C A R R O L L , J R . , Director, Chicago Area Transportation Study C . D . CuRTiss, Special Assistant to the Executive Vice President, American Road

Builders' Association H A R M E R E . D A V I S , Director, Institute of Transportation and Traffic Engineering, Uni­

versity of California D U K E W . DUNBAK, Attorney General of Colorado M I C H A E L F E R E N C E , J R . , Executive Director, Scientific Laboratory, Ford Motor Company D . C . G R E E R , State Highway Engineer, Texas State Highway Department J O H N T . HOWARD, Head, Department of City and Regional Planning, Massachusetts

Institute of Technology B U R T O N W . M A R S H , Director, Traffic Engineering and Safety Department, American

Automobile Association OSCAR T . M A R Z K E , Vice President, Fundamental Research, U. S. Steel Corporation

J . B . M C M O R R A N , Superintendent of Public Works, New York State Department of Public Works

C L I F F O R D F . R A S S W E I L E R , Vice President for Research and Development, Johns-Manville Corporation

G L E N N C . R I C H A R D S , Commissioner, Detroit Department of Public Works C. H . S C H O L E R , Applied Mechanics Department, Kansas State University W I L B U R S . S M I T H , Wilbur Smith and Associates, New Haven, Conn. K . B . WOODS, Head, School of Civil Engineering, and Director, Joint Highway Research

Project, Purdue University

Editorial Staff FRED B U R G G R A F H E R B E R T P . O R L A N D

2101 Constitution Avenue Washington 25, D. C.

The opinions and conclusions expressed in this publication are those of the authors and not necessarily those of the Highway Research Board

/VRc HIGHWAY R E S E A R C H B O A R D A

Special Report 68

CONSTRUCTION AND MAINTENANCE EQUIPMENT

A Compilation of Data on Time Utilization, Performance, and Costs

Issued Originally as Road Research Releases 1949-1960

National Academy of Sciences-National Research Council

Washington, D. C. 1962

SPECIAL COMMITTEE on

HIGHWAY EQUIPMENT

M. J . Kilpatrick, Chairman Chief, Construction Economy Branch Highiray Needs and Economy Division

Bureau of Public Roads, Washington, D. C.

H. E. Diers, Engineer of Ifeintenance, I l l i n o i s Division of Highvays, Springfield, I l l i n o i s

H. J . Ife.lm, Paving Engineer, Portland Cement Association, Chicago

H. H. lEirris, Commissioner, Virginia Department of Highways, Richmond

R. P. McKenrick, Director, Construction Indiostry Manufacturers Association, Chicago, I l l i n o i s

T. B. Plummer, Chief Engineer, V. N. Holderman and Sons, Columbus, Ohio

R. B. Stander, President, The Mansfield Asphalt Paving Company, Mansfield, Ohio

Foreword

The Board's f e c i a l Coomiittee on Highway Equipment and i t s fomer Committee on Economics of Highvay Construction and Maintenance Methods have IssTied a series of 39 informational reports in recent years on perfoimance, time utilization, and costs pertaining to equipment employed on highvay construction and maintenance work. These reports have been circtdated widely and a contin­uing demand exists for this kind of factual data. This publication brings these 39 reports togjether under a single cover and thereby provides a per­manent and convenient reference for present and future users of the research findings. These reports are grovgoed by major categories of vork, starting with portland cement concrete paving.

Issuance of additional informational reports w i l l be continued by the Special Committee. The next such report w i l l be No. hO, "In-Transit Time of Dry Cement Aggregate Batches on Paving Jobs" \dilch i s planned for publication early in 1962.

M. J . Kilpatrick, Chairman Special Committee on Highway Equipment

Contents CONSTRUCTION OPERATIONS

Concrete paving Committee Report No. 2 - Utilization of available working time

of dual drum pavers on six active portland cement concrete paving jobs in eastern states 1

Committee Report No. 30 - Cycle elements of dual drum pavers ... 3 Committee Report No. 29 - Loss in output of dml dxum pavers

can frequently be traced to batchmeter setting 6 Committee Report No. 39 - Skip cycles - 3' E dual drum pavers ... 7 Committee Report No. 36 - Observations on relation of mixing time and batch size to increased production vith 3^E dual drum pavers 10

Committee Report No. 37 - Classification of minor delays to dual drum pavers on irregular width paving work ik

Committee Report No. U - Operating cycle of two-batch trucks on Portland cement concrete paving projects 15

Committee Report No. 26 - Batch truck dumping time on paving jobs 17

Committee Report No. 6 - Productive rates of auxiliary eqiiipment on portland cement concrete paving projects 18

Committee Report No. 38 - Size of portland cement concrete paving crews 19

Bituminous paving Committee Report No. 7 - Utilization of available working time

of batch-type asphalt plants on bituminous stirfacing projects in eastern and southeastern states 21

Committee Report No. 9 - Operating cycle of trucks hatiling bituminous mix from plant to finisher on bituminous sirrf&cing projects 23

Committee Report No. 27 - Jfeintenance and repair delays of single unit dtmip trucks haviling materials for highway bituminous surfacing jobs 25

Committee Report No. 8 - Utilization of available working time of bituminous finishers on bitminous s\irfaclng projects in eastern and southeastern states 26

Power shovel grading Committee Report No. 3 - Utilization of available working time

of power shovels on ten active highway grading jobs in eastern and southeastern states 29

Committee Report No. 3^ - Utilization of available irorking time of power shovels on grading projects 31

Power shovel grading (continued) Committee Report No. 33 - Production rates of power shovels

on highway grading jobs 33 Committee Report No. 5 - Dipper load cycle characteristics

of power shovels on highway grading jobs 3''-Committee Report No. 22 - Classification of maintenance and

repair delays of 15 minutes or more experienced by power shovels on highway grading jobs 36

Committee Report No. 21 - Performance characteristics and utilization of available working time of rock trucks on power shovel highway grading operations 37

Committee Report No. 31 - Guide to hauling unit needs on power shovel grading jobs

Scraper grading crawler tractor drawn units Committee Report No. 10 - Utilization of available working

time of crawler tractor drawn scraper tmits on grading operations in eastern and southern states h2

Committee Report No. 12 - Operating cycle of crawler tractor drawn scraper units on highway grading operations in eastern and southern states ^

Committee Report No. 2k - Length of haul for crawler tractor and scraper combinations on highway grading jobs

Committee Report No. 35 - Hourly cost of large crawler tractors k6

Scraper grading rubber tired tractor draim tinits Committee Report No. 11 - Utilization of available working

time of rubber tired tractor drawn scraper \jnits on highway grading projects in southern states Ud

Committee Report No. 13 - Operating cycle of rubber tired tractor drawn scraper units on highway grading operations in eastern and southern states 50

Committee Report No. l6 - Performance characteristics of LeToumeau strper C toumapulls on highway grading projects in eastern and southern states 51

Committee Report No. 23 - Classification of maintenance and repair delays of 15 minutes or more experienced by rubber tired tractor and scraper combinations on highway grading jobs 52

Committee Report No. 25 - Length of haul for rubber tired tractor and scraper combinations on highway grading jobs

Committee Report No. 15 - Operating cycle of pvisher and puller crawler tractors working in conjunction with rubber tired tractor drawn scraper \inits on highway grading jobs in eastern and southern states 55

Other Equipment Committee Report No. ik- - Performance characteristics, pro­

duction rates, and utilization of available working time of Euclid BV loaders on highway grading projects in east-central states 57

other Eq-ulpment (continued) Committee Report No. 20 - Performance characteristics, production

rates, and utilization of total available working time of the P8eH single pass s o i l stabilizer on highway stabilization projects in eastern and central states 59

Committee Report No. 32 - Utilization of available working time of rock crushing plants on highway construction projects 62

Committee Report No. 1 - Utilization of available working time of major equipment on active highway construction jobs in eastern states 6k

HIGH' AY MAINTENANCE OPERATIONS Committee Report No. 28 - Distribution of labor time on hand patching of bituminous road siu-face 66

Committee Report No. 17 - Utilization of available working time of motorgraders on comty road work in southern states .. 67

Committee Report No. I8 - Utilization of available working time of tractor front-end loaders in borrow pits on coianty road work in southern states 69

Committee Report No. I9 - Utilization of available working time of A-cubic yard power shovel and dragline iinits on county road work in southern states 72

Three special reports on highway maintenance operations have been issued. These three reports are:

Special Title Report No.

Connecticut Highway Maintenance Production Study 8 Iowa State Highway NEiintenance Study 65 Iowa State Highway Maintenance Study, Supplement I 65

CONSTRUCTION OPERATIONS

Concrete Paving

COIvMrmE REPORT NO. 2 - APKLL 19* 9 UTILIZATION OF AVAILABLE WORKING TIME OF 3' E DUAL DRUM PAVERS ON SIX

ACTIVE PORTLAND CEMENT CONCRETE PAVING JOBS IN EASTERN STATES

Equipment production studies made on 3kE dual drum pavers during 19'*-7 and 19'*8 on active portland cement concrete paving jobs show that delays amounted to 56 percent of the total available -working time. These studies were conducted by the Public Roads Administration on six different pro­jects in the eastern United States and covered periods varying from 125 to 185 hours on each job during the active construction season.

Table 1 shows the distribution of total available working time as ob­tained from these studies during the period of observation. The total available working time i s the svm of ( l ) normal daily shift time and (2) such occasional overtime as actually worked. Thus, i f a job had a normal shift time of 8 hours daily for five days a week and 2 hours overtime was worked on one of those days, the total available working time would be k2 ho\irs. The data in Table 1 are based vpon a sample of 867 hours total available working time.

The extent of major and minor delays are also shown in Table 1. Indi­vidual time losses of 15 minutes or more in duration are classified as major delays, whereas small time losses of less than I5 minutes in duration are classified as minor delays.

TABLE 1 DISTRIBOTION OF 867 HOURS TOTAL AVAILABLE WORKING TIME FOR DUAL DRUM PAVERS ON SIX ACTIVE PORTLAND CEMENT CONCRETE PAVING PROJECTS

Percentage of total Time element available working time

Range Average Total available working time 100 100 Major delays 1/ 23-60 38 Net available working time ltO-77 62 Minor delays 2 / lh-23 3 / I8 Actml productive working time 2k-^^ Uh

1/ Individual delays of 15 minutes or more in duration. See Table 2 for detailed classification.

2 / Individual delays of less than I5 minutes in duration. See Table 3 for detailed classification.

3/ Minor delays amovint to 29 percent (18/62) of the net available work­ing time.

The classification of major delays i s shown in Table 2. These delays do not normally occur with any partic\alar regularity nor i s there much similarity between jobs.

TABLE 2

CLASSIFICATION OF MAJOR DELAYS TO DUAL DRUM PAVERS Percentage of total

NatTire of major delay available working time Rain and wet grade 15 Shortage of cement 6 ^4ajor moves on the project 6 Paver repairs 5 Waiting on auxiliary operations h Shortage of aggregates or water 1 Other 1

Total 38

The above classifications are largely self-explanatory. The time lost to auxiliary operations i s due to such, items as awaiting preparation of finegrade, setting of forms, finishing or spreading operations, and short­age of haming \mlts.

Although minor delays are ordinarily just a few seconds each in dura­tion, i t w i l l be noted from Table 1 that they amount to 18 percent of the total available working time. However, the f u l l extent of minor delays can usually be better vlsmlized by comgparing them to the net available working time rather than to the total available working time. For example when minor delays are expressed as a percentage of the total available working time, a poorly managed job with frequent major delays might show a less percentage of minor delays than a well managed job with few major delays. Th\as, a better basis for comparison between jobs i s to express the minor delays as a percentage of the net available working time.

The classification of minor delays i s shown in Table 3- Among the six jobs which were studied, the minor delays varied from 22 to ko percent of the net available working time with an average of 29 percent.

TABLE 3 CLASSIFICATION OF MINOR DELAYS TO 3'<-E DUAL DRUM PAVERS

Percentage of net Nature of minor delay available working time

Insttfficient number of batch trucks at paver 7 Batch truck dimiplng delays 4 Short forward and reverse moves of paver h Aggregate bin empty at batch plant 3 Paver maintenance and repair 2 Waiting on spreader and/or finishing machine 2 Split discharge of batch 1 Out of water 1 Waiting on placement of joints 1 Operator and personnel delays 1 Other 3

Total 29

An endeavor was made to classify minor delays in accordance with their basic cause, but In those Instances where the basic cavise could not be deteimined, the delays were classified In accordance with the apparent cause. For example, the basic cause of a delay of a few seconds or per­haps a minute or two at the paver may have been due to a temporary break­down at the batch plant; but i f this fact could not be readily deteimined •by the observer, the delay may have been charged to a shortage of batch trucks.

Puttire rei)orts w i l l deal with batch hauling, operating cycle character­i s t i c s of dual drum pavers, and other phases of portland cement concrete paving operations.

COMMHTEE REPORT NO.30 - APRIL 1955 CYCLE ELEMENTS OF DUAL DRUM PAVERS

Committee Report 29 showed that ftiil\ire to promptly recharge mixing drums of 3''-E dual drum pavers cavises loss of output on otherwise smooth running jobs. Among other factors which directly affect maximum potential production rates are ( l ) the mixing time requirement and (2) the incltision or exclusion of transfer time as mixing time. Figures 1 and 2 show the relationships of these two factors graphically.

Figures 1 and 2 are based on a charging lag of 7-0 seconds and a dis­charge lag of 1.1 seconds. For the reader who wishes to use other values the applicable formulas are shown on Figure 3« Definitions of formula values are as follows:

X = time In seconds from setting of batchmeter to next opening of the discharge chute, as allowed by batchmeter.

Y = discharge and transfer time inteirval in seconds allowed by the batchmeter. I t i s here assimed that the raised skip automatically closes the transfer chiite and resets the batchmeter simultaneously.

A = discharge lag in seconds - the time from opening of the discharge chute until concrete appears in the chute.

B = charging lag In seconds — the time from setting of the batchmeter until a l l solid materials enter drum No. 1

Figure 3 shows the sequence of operations and interrelation of the skip cycle, batchmeter cycle, and batch mixing cycle elements for a typical condition.

Maximum production potential results from minimum tatchmetetf (or paver) cycles. Minimum cycles (without job delays) for any mixing requirement result from minimum time allowance for completing discharge and transfer. For example, at 6o seconds mixing time (trsmsfer excluded), a reduction from 22 seconds to 20 seconds in the time allowed for discharge and trans­fer has the following effect: I t decreases the cycle time by 1.5 seconds (from k9.k3 to U7.95), and i t Increases potential production by 2.3 batches per hour {from. 72.8 to 75-1)•

Maximum potential production of a properly functioning paver i s rarely attained for more than a few minutes at a stretch. Inevitably, certain delays occur which slow vqp production. Ordinarily, fewer delays might be expected on those jobs with long cycles. Studies by the Production Cost Unit of the Bureau of Public Roads during the past 5 years show that this i s not necessarily the case. In fact those jobs having the least

delays quite often had the shorter cycles. Apparently the short cycle highlights delay occ\]rrences and the stlmvilus results in greater success In reducing time losses.

This tendency i s seen in the case of time taken by trucks •when dumping batches in the skip (see Committee Report 26). On jobs with short cycles the need for fast dumping -was frequently met with successful solutions. On the Grovip A jobs cited in Committee Report 26, the dunrp trucks had the least time available for dtmrplng; yet, of a l l batches dumped, only l8 per­cent delayed the paver by overrunning available dumping time (on two of the Group A jobs, the arount -was less than k percent). By 'way of compari­son, the Grotrp B jobs, with their longer batchmeter cycles, had almost twice as much time available to dtmip each batch. In spite of this advan­tage, over 70 percent of the batches dumped took more than the available time, thereby delaying the paver. Backing into the skip with previously raised dump beds i s an important aid in reducing such delays. EDwever, present designs of many trucks are such that they cannot be safely oper­ated in this manner.

40

—

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WIXINS Tl MO 01!

UE KITH TRAN

W WI1X TMir CHWGE TIWES

SFER INCLUOCO

5FEII EXCLUDED CONSIDEREO

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nSOURGE a TRANSFER - SECONDS (VVBUUE IN FORMULA)

15 20 25 30 (XSCHARGE a TRANSFER - SECONDS nrvMJUE M FORMULA)

Figure 1. Effect of discharge and transfer intervals on production

for various mixing times.

Figure 2. Effect of discharge and transfer intervals on batchmeter

cycle for various mixing times.

FORMULAS: BATCHVETER CYCLE - X • Y POTENTIAL PRODUCTION. BATCHES/HOUR = 36OO / X • Y MIXING TIME. TRANSFER INCLUDED - 2 X + Y + A - B MIXING TIME. TRANSFER EXCLUDED = 2X •(¥ - TRANSFER)* A

NOTE: SEQUENCES IN THIS DIAGRAM PROVIDE FOR SIMULTANEOUS CLOSING OF DISCHARGE CHUTE AND OPENING OF TRANSFER CHUTE SOME PAVERS PROVIDE FOR SLIGHT OVERLAPS IN DISCHARGE, TRANSFER. AND CHARGING FUNCTIONS.

(—WAS 7&fM ^ SKIP RAISM LAO

RAWNE LAS SKIP DOWN

S K I P ^ SKIP DOWN ^RAISINCi^ B.M. PERMITS RABMO SKIP

^ S K I P ^ l;^AISING>; v/////////^-B M PERMITS

RMSOM SKIP

DISCHARGE & TRANSFER • CHUTES CLOSED- DISCHARGE

CLOSED

TRANSFfR OPEN ^

DISCHARGE CLOSED

DISCHARGE OPEN

TRANSFER' CLOSED

DISCHARGE » TRANSFER CHUTES CLOSED o^NO.2

MIXING IN DRUM NO 2 MIXING IN DRUM NO I TO BUCKET] TO Noe DRUMNai

NTERDM DRIM Nai MIXING IN DRUM

BAT<»||EMORAS AND

ERMSORUMNOI k i n

Figure 3. Typical no delay cycle elements of dual drum pavers.

COMMITTEE REPORT NO. 29 - MARCH 1955 LOSS IN OUTPUT OF DUAL DRUM PAVERS CAN FREQUENTLY BE TRACED TO

BATCHMETER SETTING

Loss in potential otctput of 3^E dual drum pavers reaches 12.5 batches per ho^x^ in some cases due largely to excessive discharge and transfer time allowances in the batchmeter setting. This loss i s separate from those caused by such job delays as paver moves, batch truck and bucket dun5)lng delays, etc. Data relating to this matter are part of the infor­mation obtained from paver studies made over the past 5 years by the Production Cost Unit of the Bureau of Public Roads. Over it-1,000 batches were timed on 29 different pavers working on 2k highway jobs.

Ability to mix two batches slmultaneo\isly i s a feature of dml dnm pavers that contributes to their high productive rate. Simultaneous mix­ing prevails except during those intervals in the batchmeter (or paver) cycle \dilch allow for the discharge and transfer of batches (the skip i s raised during the transfer). The longer these intervals are, the longer the cycle becomes for any given mixing time. I t follows, therefore, that the greatest potential production (shortest cycle) w i l l result when the batchmeter setting provides the minlmm Interval needed for discharge and transfer.

The average observed time allowed by the batchmeter settings for dis­charge and transfer was 23.6 seconds for the 29 pavers. I t was 17.7 seconds for the five pavers (Grovtp A pavers) having the shortest time interval, and 32.0 seconds for the five pavers (GroTip B pavers) having the longest time interval. For a 60-second mixing time, the hourly potential production rates i / were 86.1 batches for Grotrp A pavers and 73.6 batches for Group B pavers, a difference of 12.5 batches. Hence, for each one second increase in the batchmeter setting for discharge and transfer, the Grotrp B pavers sioffered a potential loss of O.87 batches per ho\ir.

Some of the longer discharge ajid transfer intervals can be attributed to worn blades and chutes. One of the principal causes observed, however, i s simply that of ins\ifficient attention given to adjvistments of batch-meters. A properly adjusted batchmeter i s not a ciure-all for lagging production. Nevertheless, i t contributes to increased output when other elements of the organization are functioning at a high rate.

The studies also provided data on frequency distribution of actual mixing time. Actual mixing time includes those job delays during which mixing continued. I t was found that 1*0 percent of the batches were mixed less than the required time by 6 seconds or more, 28 percent were mixed within 5 seconds (plus or miniis) of the required time, and 32 per­cent were mixed 6 seconds or more over the required time. For a l l batches combined, the actvial mixing time averaged one second greater than the required mixing time.

17 The following assumptions are involved in computing hourly potential production rates: ( l ) job delays are excluded, (2) mixing time includes transfer time and discharge lag, bvtt does not include charging lag, (3) discharge lag i s 1.1 seconds from opening of discharge chute until con­crete appears in the chute, and {k) charging lag i s 7-0 seconds from the time the batchmeter i s set until a l l solid materials are in the drum.

COMMITTEE REPORT NO. 39 - December 1960 SEEP CYCLES - 3 +5 DUAL DRUM PAVERS

Field studies on the performance of 3' E dual compartment pavers show that delays averaging seven seconds or more per batch resvilt from a com­bination of two causes:

1. Slow batch truck performajice at the skip 2. Excessively long skip cycles; i.e., slow lowering of skip.

S k i l l f u l operators recognize that paver moves and dumping of the bxicket should be accomplished diu-ing the skip xsp and down cycle for efficient paver performance. They consistently accomplish these opera­tions without extending the skip cycle. On the other hand, extended skip cycles incurred by less s k i l l f u l operators add iip rapidly in paver delays. Many of them can be avoided.

The following comparison of average skip cycle time for 10 slow pavers and 10 fast pavers from a group of 35 pavers studied shows considerable variation.

Skip cycle time (sec) 1/ Pavers Job rang'e Average 10 slow 22 - 26 23 10 fast 16 - 19 17 Difference 6

Fig\ire 1 shows this 6-second difference graphically in the frequency distribution curves of skip cycle time for the two grovtps of pavers. I t i s apparent that some operators are clearly more time conscious than others. Lowering the skip 6 seconds sooner means just that much more time available for reloading the skip, and consequently an opportunity to reduce truck dumping delays. Short but frequent paver moves, and prompt bucket dumping are essential in achieving a minimum skip cycle. Even i f the operator accomplishes these two operations efficiently, he s t i l l does not know how soon to lower the skip because he cannot see when i t i s empty.

Encoiuaging r e s u l t s have been obtained from studies of a paver equipped with a signal which indicated to the operator when to lower the skip. To accomplish this, an easily adjusted 12-vDlt signaling xmit 2/has been assembled using commercial components and i s being f i e l d tested by the Office of Research, Bureau of Public Roads. This imit, which can be attached to any paver, signals the operator at the proper instant he shovild start lowering the empty skip. I t i s activated by the rising skip as i t nears i t s vertical position and i t can be set to cause a signal light to come on after a preset interval (adjustable from 0 to 15 sec), followed by a reminder buzzer 3 to 5 seconds later. The light indicates to the operator that the skip i s empty and that i t should be lowered immediately. A few t r i a l and error adjvistments of the dial - v t I I I deter­mine the minimm time setting for different rates of flow of material through the skip throat.

17 Meastired from instant skip starts up to instant i t ret\ims to ground. 2/ Parts l i s t and schematic wiring diagram are attached.

8

17 seconda

6 SECONDS

Average 23 seconds

Seconds

Figure 1. Frequency distribution of skip cycle time for ten fastest and ten slowest of thirty-five 3k-E dual compartment pavers studied.

Figure 2. Timing unit and skip micro switch ( J ) ,

Schematic wiring diagram f o r skip signaling vinit

MS No. 1 Timer motor MS No Nonnal

position Normal

position clutch

Timei^ t i n i t termirials

Signal l i g h t (?)

O Switch (5)

Switch (D ® Switch 0

@

® 12v DC ) Spring loaded micro switch - closed by pressvtre finger attached t o paver skip.

) Master on-off switch - external toggle. ) Delay huzzer on-off switch - toggle (optional) ) 3- or 5-second delay relay tube with connectors numbered (optional). ) Power can usually be obtained from s t a r t e r switch or battery terminals.

NOTE: NO COMMON GROUND. ALL COMPONENTS INSULATED FROM PAVER AND CASE.

• I n t e r n a l w iring diagram f o r 12-volt DC timer

- — -1 Wiring diagram f o r y ^ Wiring diagram I [switches, signal z = f o r delay I I l i g h t and power Z : bijzzer • — —• sottrce (optional)

on External toggle switch (?) turns on timing u n i t •when f l i p p e d to the "c„ position. Micro switch (3) i s attached t o paver body and i s actuated by a pro­j e c t i n g pressure finger or tension spring attached t o the skip as i t nears i t s v e r t i c a l p osition.

Vhen (3) closes, the timer motor s t a r t s . As the red pointer on the timer \ i n i t reacKes zero, MS (micro switch) No. 2 i s tripped completing the signal l i g h t and buzzer c i r c u i t . An instant l a t e r , MS No. 1 i s tripped stopping motor. As the skip starts down, micro switch opens the c i r c u i t , turning o f f the signal l i g h t and buzzer, and releasing the magnetic clutch which permits the red pointer t o r e t i i m t o i t s preset position f o r the next cycle. Switch i s vised t o disconnect buzzer c i r c u i t , i f desired.

10

Quantity 1 each y

2 "

1 " 1 " 1 " 1 "

1 " 1 " 10-ft 20-"

1 tube

(D

Parts l i s t f o r skip signaling t i n i t J/ Description

Timer u n i t , Model TDAB, 15 sec range, l/U-sec i n t e r ­vals, 12-v DC Micro switch. Model DTU-2RN2

Toggle switches, H. anith 510 SPST ,Delay relay tube, 12N03 (3-sec) or 12N05 (5-sec) Tube socket, XS-8 Fuse and holder, 5 anip Truck clearance l i g h t assembly, 12-volt DC Resistor, 2 ohm Buzzer, 6-volt Hookiip wire No. l8 Power source and skip micro switch hookup wire No. lU Assorted terminal connectors Caulking compound f o r dust-proofing timer case

Manufacturer I n d u s t r i a l Timer Corp. l407 McCarter Highway Newark U, N. J. Micro Switch Division of Minneapolis Honeywell Regulator Company Freeport, 111.

Amperite Company New York, N. Y.

17 Approximate cost of component parts and materials i s $90. 2/ Other comrpanies may manufacture an equivalent timer.

N\imbers correspond t o those on schematic wiring diagram.

COMMITTEE REPORT NO. 36 - JUNE 1958 OBSERVATIONS ON RELATION OF MIXING TIME AND BATCH SIZE TO INCREASED

PRODUCTION WITH 3^E DUAL DRUM PAVERS

Batch size and mixing time i / are two matters of interest t o highway engineers concerned with portlaaid cement concrete mixed i n 3J+E d m l drum pavers. Each of these factors d i r e c t l y influences production rates on highway paving work and, hence, cost of the finished product. Studies made by the Production Cost Section of the Bureau of Public Roads reveal information lAiich bears on the subject of production rates.

For •v*atever batch size that may be specified on a p a r t i c u l a r job, the quantity of concrete produced i s simply a function of the number of batches. I n t u r n , the number of batches produced i s determined by length of the paver cycle and diiration of delays.

With a dual drum paver, a batch of concrete mixed 60 seconds can be produced i n approximately \\ seconds. This i n t e r v a l of machine time i s called the paver cycle. During t h i s Ul-sec cycle the skip i s raised, emptied, £uid lowered and then reloaded by a batch truck. Moving the skip through i t s cycle takes abotrt I8 of the ln-sec paver cycle time. The

1/ Defined as the i n t e r v a l from entrance of a l l aggregate i n the mixing drum v i n t i l discharge begins.

11 difference tetveen l8 seconds and kl seconds i s the time available f o r re­loading the skip. I f the difference of 23 seconds i s exceeded, the paver i s delayed.

Reloading the skip involves three separate time elements as follows: ( l ) hacking the hatch truck irp t o the skip; (2) dumping the batch into the skip ajid getting the truck out; and (3) an i n t e r v a l req\iired f o r the paver operator t o react a f t e r the batch truck clears the skip. This l a t t e r i n t e r v a l can be assmed to require two seconds; although, a value of one second might be applicable i n some cases. Thus, steps ( l ) and (2) must be completed i n 21 seconds or a delay v i l l occ\ir.

Figvire 1, ciorve "A", shovs a cumulative frequency d i s t r i b u t i o n of the average time taken by batch trucks f o r backing up t o the skip on seven fast jobs. Curve "B" shows average back-itp time f o r three slow jobs. An allowance of 3+ seconds f o r backing ttp permits 80 percent of the trucks represented by curve "A" t o complete the operation without delaying the paver. When t h i s 3 seconds i s subtracted from the available 21 seconds fo r reloading the skip, i t leaves l8 seconds to dump the batch and get the truck out of the skip.

Figure 2 shows several freqtiency d i s t r i b u t i o n s of the time teJsen by trucks t o dump a batch i n t o the skip and p u l l out. Cxurve "E" i s an average of f i v e t y p i c a l l y fast jobs employing conventional 2-batch trucks. Curves "C" and "D" are considered as special cases. They involved k- and 5-batch trucks -vrtiich could be raised p r i o r t o dumping the f i r s t batch and \rtiich were l e f t i n that position f o r dumping the 3 or If subsequent batches. This i s a practice •vdiich either could not be, or was not followed i n emy of the so-called t y p i c a l l y fast jobs shown by c\arve "E". 2/ C\arve "F" i s the average f o r three slow jobs using 2-batch trucks.

Since the type of batch truck equipment represented by curve "E" i s more often fovmd on paving work than the larger k~ or 5-hatch trucks, only t h i s curve w i l l be examined i n d e t a i l . I t can be said of the jobs represented by cxurve "E" that every e f f o r t was made to expedite reloading the skip. But note that only 70 percent of the batches were dumped i n l8 seconds or less. Nonetheless, t h i s might be considered on many jobs t o be an accept­able l e v e l of performance with the equipment involved.

Now consider the ef f e c t of reduced mixing time on t h i s operation. The mechanism of a d m l drum paver i s such that changing the required mixing time does not change the paver cycle by a corresponding amovmt. I n f a c t , the change i n the paver cycle i s only one-half of the amount by which mix­ing time i s changed. Thxis, f o r example, i f mixing time Is reduced from 6o t o 50 seconds, the required paver cycle time w i l l be cut by only 5 seconds. Since the skip up and down cycle, the truck back-up time, and the paver operator's reaction time axe r e l a t i v e l y constant, the reduction i n mixing time must be absorbed i n the time available f o r dumping the batch i n the skip. Consequently, instead of having l8 seconds i n which t o dump the batch i n the skip, the time available f o r t h i s operation becomes 13 seconds.

Looking again at Figure 2 i t may be noted on the "E" curve that only 15 percent of the batches would be dimrped i n less than 13 seconds; the

2/ A b i l i t y t o keep the truck bed raised p r i o r t o dumping a batch i s gen­e r a l l y recognized as a means to expedite reloading the skip. However, -use of k- or 5-batch trucks with t h i s c a p a b i l i t y should not be construed as guaranteeing fast reloading. One of the slowest batch dumping operations studied was on a job where i»-batch trucks were Tosed.

12

/ (n / SI lu / (9 /

i ii

/ */

remaining 85 percent voiild cause a delay. While t h i s -would hardly q u a l i f y as an acceptable l e v e l of per-fonnemce, an a l e r t contrac­t o r -vAio minimizes his losses i n recharging the skip covild, no doubt, realize a sub­s t a n t i a l advantage from redvtced mixing time.

By using the same con-stGuits f o r the skip iip and dovn cycle, the truck back-yxs time, and the paver op­erator's reaction time, an allo-wable time f o r dumping the batch i n the skip and getting the truck out may be computed f o r various mix­ing times. Figure 3 shows these computed values f o r mixing times between 24 and 120 seconds. With a 70-sec mixing time, f o r example. Figure 3 shows that 23 seconds are available f o r dumping. Referring t o curve "E", Figure 2, i t may be noted that 92 percent of the batches could be dumped i n 23 seconds or less with the 2-batch trucks represented. Similarly, an average of curves "C" and "D" TOUld indicate that mixing time as low as 37 seconds might be p r a c t i ­cal with the U- or 5-tetch trucks represented.

Stiadles made by the Production'Cost Section Indicate that delays aver­aging 19 seconds per batch woidd be incurred from a l l catises when a h\-second paver cycle (nominal f o r one-mln\ite mixing) i s \ised. By reducing mixing time from 60 t o 50 seconds, the paver cycle time i s reduced t o 36 seconds. Of the 5 seconds thus saved, i t has been computed that additional delays t o t a l i n g 3 seconds would be inctmred when 2-batch trucks of the type represented i n curve "E" are used. Most of t h i s 3 seconds wovild be l o s t due t o I n a b i l i t y t o reload the skip i n the allowable time. This adds vtp t o indicate that a batch of concrete could be produced every 58 seconds (If-l _ 5) + (19 + 3) Instead of every 60 seconds (Ul + I9).

Based on a batch size 10 percent above rated capacity, t h i s 2 seconds' savings Increases production by aboxtt 3 cubic yards of concrete per hour. An equal Increase i n production could also be attained with a one-minute mix by increasing the 10 percent allowable overload ttp t o 13+ percent.

Aside from considerations of q u a l i t y of the concrete mix, two conclu­sions can be drawn with respect t o the matter of higher production:

Figure 1. Cumulative frequency d i s t r i b u ­tions of average back up to skip time f o r

two groups of jobs.

1. I f f u l l benefit i n the form of increased production i s t o be ob­tained from a reduced mixing time, i t follows that present methods of re­loading paver skips with conventional 2-batch trucks must be substamtially improved.

13 2. Within the c a p a b i l i t i e s of 3 E dual drum pavers t o handle larger

batches, an Increase i n batch size offers as good an opportunity f o r i n ­creased production as does decreased mixing time which reduces the paver cycle below hi seconds.

X 6 0

o 0. 40 if

© ©/ /

to 1 ^ f <> 1 1 a: 1 vi t - 1 sc

SI ff/ */ /

i s < I ' /

SI

s'l SI

d/

* 1 ^ 1 to I (D| ° V

^ CO Si

&

*/ Of iy / < II lis c 1 f

/ /

16 21 SECONDS

Figure 2. Cum\ilatlve frequency d i s t r i b u t i o n s o f average time t o dimrp one batch i n t o the paver skip and get the truck o\it.

Constants used Skip cycle time l8 sec Back up time 3 " Operator's reaction time 2 " W 40

MIXING TIME-SECONDS

Figure 3. Available time f o r dumping the batch i n t o the skip and getting the truck

out.

11 COMMITTEE REPORT NO. 37 - OCTOBER 1958

CLASSIFICATION OF MINOR DELAYS TO DUAL DRUM PAVERS ON IRREGULAR WIDTH PAVING WORK

One of the production problem areas i n portland cement concrete paving work i s i r r e g u l a r or nonstandard widths such as tised f o r deceleration lanes, ramps, f l a r e s , etc., a t interchanges. Production rates on t h i s type of paving are one-third less than on mainline paving. An indication of the degree of d i f f i c v i l t y experienced i n t h i s work vhen using dual drum pavers i s shown by the comparison of minor delays i n Table 1. 1/

The magnitude of the delays was determined from studies conducted by the Bureau of Public Roads on f i v e projects i n eastern States. Each project included both mainline paving and a varied assortment of irr e g u l a r or non­standard width paving around interchanges. The t o t a l period of study ex­ceeded 500 hours of scheduled working time and was about equally divided between both types of work.

Table 1 shows ( l ) the p r i n c i p a l types of delays encountered, (2) the percentage that each type i s of the amovmt of net available working time devoted t o the respective work 2/, (3) the percentage by which delays on the i r r e g u l a r work exceeded delays on mainline work, and (k) the range i n t o t a l percentage based on I n d i v i d m l job t o t a l s .

Most of the difference between these two types of work i s accounted f o r by the absence of extensive machine f i n i s h i n g operations and the practice of spreading concrete with the bucket. The l a t t e r occurs i n the form of s p l i t batches and during the careful placement of concrete by alt e r n a t e l y opening and closing the bucket \ * i i l e d i s t r i b u t i n g the batch. Some reduc­tions i n the difference accoiinted f o r by delays due t o moving, batch truck operation, and truck svtpply co\ild probably be accomplished with r e l a t i v e ease. I t i s most l i k e l y , however, that a reduction i n these categories would be of f s e t i n part by increased delays due to spreading and f i n i s h i n g operations.

Further analysis on these two types of work revealed that the difference of 22 percent accounted f o r 17 batches per hour.

TABIE 1 PERCENTAGE DISTRIBUTION OF MINOR DELAYS EXPERIENCED BY

DUAL DRUM PAVERS ON HIGHWAY PAVING JOBS Percent of net available working time ~Tn (21 (3) Ffeinline I r r e g u l a r Difference

Type of delay paving paving (2) min\is ( l ) Paver operation:

Moving k 6 2 Spreading concrete with bucket 2 11 9

Finishing operations 2 8 6 Batch trucks:

Operations at the skip 5 7 2 Sttpply amd other 9 13 k

A l l other 9 8 -1 Total 31 53 22

Job range 11 t o 5* 31 t o 68 11 to l/ Minor delays are individual time losses of less than 15 minutes each. 2/ Net available working time i s the time remaining a f t e r delays of 15

minutes or more each are subtracted from scheduled working time.

15 COMMITTEE REPORT NO. 4 - MAY 19 +9

OPERATIMG CYCLE OF TWO-BATCH TRUCKS ON POBTIAND CEMENT CONCRETE PAVING PROJECTS

ffiiullng u n i t studies made on two-batch trucks on portland cement con­crete paving projects show that each truck spends a t o t a l of s l i g h t l y over 12 minutes per t r i p i n the batch plant, at the paver, and I n mlscellaneoxis waits and delays. The average road speed was observed to be between 20 and 25 miles per hoiir.

These data were obtained from studies made by the Production Cost Unit of the Public Roads Administration on 7 d i f f e r e n t projects i n the eastern and southern Ifaited States over the past l8 months. About 80 trucks were observed f o r a t o t a l of 950 truck-hours of operation. Dual drum pavers were employed on 6 of the projects, and a single drum \ i n i t was vised on the remaining job.

Table 1 i s a svmmiary of data r e l a t i n g to the major elements of the batch truck cycle.

TABLE 1 SUMMARY OF CYCLE DATA RELATING TO THE OPERATION OF TWO-BATCH

TRUCKS ON PORTLAND CEMENT CONCRETE PAVING PROJECTS Element Range Average

1. Time I n batch plant, per t r i p 3>0-5.7 min k.2h min 2. Time at paver, per t r i p 1-9-3.1 " 2.148 " 3. Miscellaneous waits and delays,

per t r i p 1/ 2.5-8.8 " 5•'+5 " k. Total time constant (sum of items

1, 2, and 3) 2/ 10.5-15.2 " 12.17 " 5. ffiiul distance 0.9-h.J miles 2.11 miles 6. Haul speed, loaded l6.6-31.0 ml/hr 21.1 mi/hr 7- Return speed, empty 17.8-37-3 " 23.5 1/ Minor waits and delays less than 15 minutes i n dioation. 2/ For any given job, items 1, 2, and 3 show l i t t l e v a r i a t i o n i n r e l a t i o n t o the length of haul. Accordingly, these items are frequently termed "time constants."

The ranges shown i n Table 1 are job averages. On several of the pro­jects the variations from day t o day frequently exceeded the ranges which are shown. For example, the haul distance on a partlc\alar job may have varied from 0.5 t o 6.0 miles, but only the overall Job average f o r t h i s job was considered viien l i s t i n g the entries i n Table 1.

Average haul and return speeds i n excess of 30 miles per hour were ob­tained on only one job; the speeds on the other 6 jobs ranged from 16.6 t o 29.3 miles per hour over paved or reasonably well graded earth roads. On the job which had the highest average speed, 31-0 miles per hour loaded and 37.3 miles per hour empty, the hauling was done over a l e v e l and newly paved road closed to t r a f f i c .

The times involved i n various operations at the batch plant and at the paver are shown i n Table 2.

16 TABLE 2

OPERATING CYCLE ELEMIHTS IN THE BATCH PLANT AND AT THE PAVER FOR TWO-BATCH TRUCKS ON PORTLAND CEMENT CONCRETE PAVING PROJECTS

Average time i n minutes

1.98

Cycle elen\ent 1. Time I n batch plant, per t r i p

a. Driving and maneuvering i n plant yard b. Set up cement compartments, lock ^ t e s ,

secvire canvas cover, etc. 0.U3 c. Load aggregates 0.8k d. Load cement ' 0.99

Total time I n batch plant, exclusive of waits and delays k.2k

2. Time at paver, per t r i p a. Maneuvers (switching and turning) upon a r r i v a l

at paver O.77 b. Exchange 0.26 c. Dump batches 1* 5

Total time a t paver, exclusive o f waits and delays 2.1(8

3. Miscellaneous waits and delays, per t r i p 1/ a. Walt at aggregate and cement bins 0.33 b. Walt at paver 3-^1 c. Minor delays, other than waiting I.71

Total waits and delays 5-'*5 1/ Minor waits and delays less than 15 minutes i n duration.

The above items are l a r g e l y self-explanatory. The exchange time o f 0.26 minute at the paver i s the I n t e r v a l of time from the moment one truck drives o f f the skip a f t e r having duzsped I t s second batch i i n t l l the moment the next truck backs up onto the skip. This i s a very c r i t i c a l time I n ­t e r v a l that sho\ild be reduced t o a minimum, p a r t i c u l a r l y on dual drum paver operations.

Only i n d l v l d m l minor delays t o the truck of less than I5 minutes each I n duration are Included i n the average wait and delay time o f 5•'('5 minutes. A l l major delays o f 15 mintttes or more have been excluded from Tables 1 and 2.

OPERATING CYCLE OF THREE-BATCH TRUCKS ON POETIAND CEMENT CONCRETE PAVING PROJECTS

From two studies made thus f&r on three-batch trucks on portland cement concrete paving projects I t I s found that each truck spends about 5.5 minutes i n the batch plant euid k.O minutes at the paver on each t r i p . I n addition, about 5*8 minutes per t r i p are l o s t i n minor waits and delays. The average havl and ret\im speeds were observed t o be 22.6 and 25.0 miles per hotjr, respectively. Because of the l i m i t e d number o f studies involved, the foregoing average may nbt be p a r t i c u l a r l y representative.

17 COMMITTEE REPORT NO. 26 - DECEMBER 1953 BATCH TRUCK DUMPING TIME ON PAVING JOBS

The average time f o r batch trucks t o dimip a batch i n the skip of a 3UE dual drum paver varies between jobs by more thaii 350 percent. Where dxmp-ing times are excessive, delays t o the paver may be substantial. On some Portland cement concrete paving jobs such delays have averaged better than an hoirr i n each 10-hr work day.

Data on the dumping time o f batch trucks were obtained from studies con­ducted by the Prod\iction Cost Unit of the Bureau of Public Roads. These studies were made over the past 5 years on 12 paving jobs selected at ran­dom. Over 21,000 batch dumpings were timed f o r ik d i f f e r e n t 3kE d m l drum pavers.

The time available f o r dumping of the batch trucks, "skip down" time, i s dependent on the paver cycle time f o r which the batchmeter i s set. This time varies from job t o job. Unless dumping maneuvers are completed with­i n t h i s skip down time the paver w i l l be delayed. These truck maneuvers are:

1. Backing onto the skip. This maneuver starts when the skip h i t s the groioxd and ends vben the waiting batch truck i s backed up t o a point \diere i t s bed obstructs the skip.

2. Duniplng the batch. This maneuver starts when the bed of the truck obstructs the skip and ends •when the truck i s again clear of the skip, a f t e r dumping i t s batch.

The average time required t o back onto the skip (item 1) was about 3.5 sec f o r a l l jobs combined. On individual jobs variations o f I.5 sec either greater or less than the average, were observed.

With respect t o dumping the batch (item 2) there were wide variations among the individual jobs. An indication of the extent of these varia­tions i s obtained "by comparing the three jobs (Grovtp A jobs) having the least dumping time per batch with the three jobs (Group B jobs) having the most dumping time per batch. Of the Group A jobs, two had l<-batch trucks, and one had 2-batch trucks. Of the Grovop B jobs, one had If-batch trucks, one had both 2- and. 3-batch trucks, and one had 2-batch trucks.

Average time taken Average "skip down" time by truck t o dimrp available f o r dumping one one batch i n the batch i n the skip (item 2)

Jobs skip withoTit delay t o paver sec. sec.

Groitp A - the 3 Jobs where trucks took the least time to dump t h e i r batches J.k 10.8

Groitp B - the 3 jobs where trucks took the most time t o dvmrp t h e i r batches 26.6 19.8

Because of differences i n paver cycles, the Groitp A jobs had 9 sec less skip down time available f o r dmplng than did the Group B jobs. This handi­cap was overcome, however, by more rapid batch dumping. On the average, the trucks on Groitp A jobs dimiped each batch i n less than a t h i r d of the time taken on the Grovtp B jobs. On the Group B jobs, the average time t o dump one batch exceeded the skip down time by 6.8 sec. The t o t a l of such delays amoimt to 10 percent or more of the working time on some jobs.

18 F i e l d observations indicated no noticeable difference i n the exercise

of good safety practice among the various jobs. Thais, i f the batch dmp-ing time on Group A jobs i s considered as a reasonable standard of per­formance, i t i s apparent that excessive and constantly recurring delays caused by slow dumping of the batch can be reduced i n many cases. Use of suitably designed batch trucks, hoisting of the body i n readiness f o r back­ing onto the skip, coaching of truck drivers, smd h i r i n g of a capable dump-man (or spotter) t o di r e c t the batch trucks i n t h e i r dmping maneuvers w i l l pay dividends i n keeping paver delays from such causes to a minimum.

COMMITTEE REPORT NO. 6 - JUNE 19^9 PRODUCTIVE RATES OF AUXILIARY EQUIPMENT ON PORTLAND

CEMENT CONCRETE PAVING PROJECTS

Equipment performance studies made on portland cement concrete paving projects reveal that productive rates of a u x i l i a r y equipment average about 66 percent greater than the productive rate of the paver. These studies were conducted by the Production Cost Unit of the Public Roads Administra­t i o n on 36 d i f f e r e n t units of equipment used on eight d i f f e r e n t projects i n the eastern United States dtiring the past 18 months.

For the purpose of t h i s report, the production of avixiliary equipment has been converted t o eqiiivalent units of paver production. The hourly productive rate of the a u x i l i a r y equipment i s then expressed as a percent­age of the hourly productive rate of the paver. A l l delays are excluded. Table 1 i s a summary of the restilts obtained.

TABLE 1 PRODUCTIVE RATES OF AUXILIARY EQUIPMENT ON PORTLAND CEMENT CONCRETE

PAVING PROJECTS Percentage of the prodvictive rate of the paver Range Average

90-227 129 98-322 197 79-381 17'<-

- 166

Location and type of equipment 1. At the batch plant - aggregate batch bins,

cement bins, \jnloaders, cranes 2. I n fr o n t of the paver - form graders, f i n e -

graders, subgrade planers 3- Behind the paver - spreaders and finishers ^1. Average, a l l units of a u x i l i a r y equipment

The a u x i l i a r y equipment i n Table 1 includes p r i n c i p a l l y those i n d i v i d ­ual mechanized units whose breakdown during a working day would be most l i k e l y t o cause a shutdown of paving operations. Batch trucks are not included.

The ranges shown i n Table 1 are job averages obtained during periods when operations were considered t o be reasonably t y p i c a l . On several pro­jects the variations from day t o day frequently exceeded the ranges -vrtiich are shown. For example, a f i n i s h e r may o r d i n a r i l y have a productive rate 150 t o 200 percent of the paver rate, but on a hot, windy day with low h m i d i t y , the f i n i s h e r may have so much d i f f i c u l t y i n i t s operations that i t s productive rate may at times be reduced t o as low as 50 to 60 percent of the paver rate.

On concrete paving jobs, i t i s a common occurrence f o r paver production to be cu r t a i l e d by shortages of hatiling u n i t s , dumping delays, moves.

19

paver maintenance and repairs, and so on. In such Instances the productive rate of a-uxiliary equipment can be less than that of the paver and s t i l l not cavise any delays t o the paver. When the production of a u x i l i a r y equip­ment fla i l s behind t o the extent of being l i k e l y t o i n t e r f e r e with paver' production, the a u x i l i a r y equipment usually w i l l be worked additional time either early i n the morning p r i o r to paving or i n the evening a f t e r the paver has shutdown.

COMMITTEE REPORT NO. 38 - NOVEMBER I96O SIZE OF PORTLAND CEMENT CONCRETE PAVING CREWS

ProdTiction studies of portland cement concrete paving operations reveal a marked v a r i a t i o n between the size of crews used f o r each project and f o r each paving method. Slip form pavers were encountered on three of the pro­j e c t s . These studies were made by the Office of Research, Bureau of Public Roads.

Table 1 shows that s l i p form paving crews had an average of 11 less men than conventional form paving crews where one paver was used. The d i f f e r ­ence Increased to 20 men \diere conventional form paving \jas performed with two pavers. On the one-paver jobs i t may be noted that there i s an i n t e r ­nal v a r i a t i o n i n the difference depending on •vrtiether one-lane or two-lane conventional form paving was performed. These data do not include those men used f o r batch hauling or f o r operation of the batch plant and bulk delivery of materials.

The two groupings \ased under the heading "Operations performed" were considered t o be the most practicable becavise of -multiple and overlapping assignments t o various crew members on several jobs. Further, the basic data indicated that forming and subgradlng crews were r a r e l y Involved with the paving or f i n i s h i n g operations.

TABLE 1

COMPARISON OF CREW SIZE Ntmiber of men tised

Slip form Conventional Conventional Conventional paving 1/ paving 2 / paving 3 / paving 4 / Two- -lane Two- •lane One- •lane Two-lane one paver one paver one paver two pavers

Operations Aver­ Job Aver­ Job Aver­ Job Aver­ Job performed age range age range age range age range

Paving, f i n i s h i n g 26-28 18-1^1 j o i n t s ajcid ciirlng 27 26-28 27 18-1^1 22 17-29 31 23-37

Forming and/or 17-to 22-41 21-42 subgradlng 13-15 25 17-to 30 22-41 30 21-42

Total kl 3 9 - ^ 52 35-81 52 41-70 61 49-69

1 3 projects 12 projects 13 projects 12 projects

20

Marked variations i n the crew organization of some jobs were noted, as shown i n Table 1, but these were not associated d i r e c t l y with rates of production. Performance studies of dual drum pavers, vhich w i l l be reported i n a subsequent release, indicate that rates of production on jobs where only one paver i s tised can consistently be maintained at 6o batches or 83 cubic yards per working hour when a 10 percent overload i s allowed. Where 10-inch pavements are being placed, the 83 cubic yards w i l l res\alt i n a y i e l d of 3OO square yards. Performance studies on the s l i p form machine indicate that i t has adeqiiate capacity t o process over 60O square yards of pavement per hoiir. Whether the use of a second dual drum paver i n com­bination with the s l i p form machine would actually r e s u l t i n additional labor savings, such as indicated by Table 1, has not been determined.

21

Bituminous Paving COMMITTEE REPORT NO. 7 - JULY 19 +9

UTILIZATION OF AVAILABLE WORKING TIME OF BATCH-TYPE ASPHALT PLANTS ON BITUMINOUS SURFACING PROJECTS IN EASTERN AND SOUTHEASTERN STATES

Equipment performance studies being conducted by the Production Cost Unit of the Public Roads Administration on active bituminous surfacing jobs on r u r a l highway reveal that delays t o batch-type asphalt plants amount t o 55 percent of the t o t a l available working time. These studies were conducted over the past 18 months on six d i f f e r e n t projects I n east-em and southeastern States on plants ranging i n size from 1 t o 2|- tons, and covered periods varying from 80 t o 230 hours on each job.

Table 1 shows the percentage d i s t r i b u t i o n of 863 hours t o t a l available working time as obtained from the studies.

TABLE 1

DISTRIBUTION OF 863 HOURS TOTAL AVAILABLE WORKING TIME FOR BATCH-TYPE ASPHALT PLANTS ON SIX ACTIVE BITUMINOUS SURFACING PROJECTS

ON RURAL HIGHWAYS

Percentage of t o t a l Time element available working time

Range Average

100 100 25-65 k2 35-75 58 7-21 y 13

21-68 h3

Total available working time 1/ Major delays 2/ Net available working time Minor delays 3/ Actual productive time 1/ The sum of ( l ) normal d a i l y s h i f t time and (2) such occasional

overtime as actually worked. 2/ Individual delays of 15 minutes or more i n duration. See Table 2

f o r detailed c l a s s i f i c a t i o n . 3/ Individual delays of less than 15 minutes i n duration. See Table

3 f o r detailed c l a s s i f i c a t i o n . h/ Minor delays amount t o 22 percent (13/58) of the net available

working time. As indicated by the ranges of percentages i n Table 1, there i s con­

siderable v a r i a t i o n i n the u t i l i z a t i o n of time among jobs. The p r i n c i p a l single item causing these variations was weather, which varied from 1 to k6 percent among the several projects. The extent of major delays due t o weather and other delays of 15 minutes or more i n duration i s shown i n Table 2.

22

TABLE 2

CLASSIFICATION OF MAJOR DELAYS TO BATCH-TYPE ASPHALT PLANTS

Percentage of Nature of major delay t o t a l available

working time Weather: r a i n , wet, cold 28 Delays at the paving s i t e 5 Plant maintenance and repairs 3 Shortages of aggregates or asphalt 3 Lack of hauling units at plant 2 Other 1

Total ^2

The c l a s s i f i c a t i o n of minor delays i s shown i n Table 3. Althoiigh minor delays are o r d i n a r i l y j u s t a few seconds each i n duration, i t w i l l be noted i n Table 1 that they amount to 13 percent of the t o t a l available working time. However, the f u l l extent of minor delays can usually be better visualized by comparing them to the net available working time. For example, when minor delays are expressed as a percentage of the t o t a l available working time, a job with frequent and extensive major delays, such as bad weather, tends t o show a lesser percentage of minor delays than a job with few major delays. Thus, a better basis f o r indicating the extent of minor delays i n r e l a t i o n t o the production operation i s to express them as a percentage of the net available working time.

For the batch-type asphalt plants employed on the six jobs which were studied, the minor delays varied from 9 t o kl percent of the net available working time with an average of 22 percent. Waiting f o r dried aggregate from the dryer u n i t accounted f o r h a l f of the minor delays t o plant production.

TABLE 3

CLASSIFICATION OF MINOR DELAYS TO BATCH-TYPE ASPHALT PLANTS

Percentage of Nature of minor delay net available

working time Shortage of dried aggregate 11 Lack of haiiling units at plant 5 Plant maintenance and repairs 2 Operator and personnel delays 2 Other _2

Total 22

An endeavor was made to c l a s s i f y both major and minor delays i n accord­ance with t h e i r basic cause, but i n those instances where the basic cause could not be determined, the delays were c l a s s i f i e d i n accordance with the apparent cause. For example, the basic cause of a delay to the plant r e s u l t i n g from a temporary lack of hauling units may have been due to

23

another delay elsewhere on the job; but i f the cause of t h i s delay could not be readily determined by the observer, the delay was charged to the apparent cause - lack of hauling l u i i t s at the plant.

COMMITTEE REPORT NO. 9 - AUGUST 191 9 OPERATING CYCLE OF TRUCKS HAULING BITUMINOUS MIX FROM PLANT TO

FINISHER 1/ ON BITUMINOUS SURFACING PROJECTS

Studies made on trucks hauling bituminous mix from the plant to the fi n i s h e r on bituminous s\irfacing projects show that the t o t a l time each truck spends at the plant, at the f i n i s h e r , and i n miscellaneous waits and delays averages more than one-half hour each roxuid t r i p . The average road speed was observed t o be about 30 miles per hour. These data were obtained from studies made by the Production Cost Unit

of the Bureau of Public Roads on nine d i f f e r e n t projects i n the eastern and southeastern States over the past 20 months. About 95 trucks of var i ­ous sizes and makes were observed f o r a t o t a l of 1,050 truck hours of operation. The average load carried by the trucks was 7.U tons, and the average haul distance was 7-9 miles. Most of the hauling was done over surfaced roads that were well maintained.

Table 1 i s a summary of data r e l a t i n g to the major elements of the truck cycle.

TABLE 1

SUMMARY OF CYCLE DATA RELATING TO THE OPERATION OF TRUCKS HAULING BITUMINOUS MIX ON BITUMINOUS SURFACING PROJECTS

Element Time i n plant per t r i p , ex­

cluding waits and delays Time at f i n i s h e r per t r i p , ex­

cluding waits and delays Waits and delays per t r i p Total time constant {svaa of

items 1, 2 and 3) Haul speed, loaded Return speed, empty

Range

3.8-16.1 minutes

3.0- 7.9 minutes 10.6-26.7 minutes

22.0-50.3 minutes 16.3-37-6 miles/hr 22.3-^1.8 miles/hr

Average

0.2 minutes

5.3 minutes 16.6 minutes

32.1 minutes 27.8 miles/hr 32.3 miles/hr

Delays to the trucks during periods when the plant or the fi n i s h e r i s shut down because of repair, material shortages, moves, and so on, have been excluded when the shutdown i s 15 minutes or more i n duration. The ranges shown i n Table 1 are job averages. On several of the pro­

jects the variations from day t o day frequently exceeded the ranges which are shown. For example, the haul speed on a pa r t i c u l a r job may have varied from 12 to 20 miles, but only the ove r - a l l average f o r t h i s job was con­sidered when l i s t i n g the entries i n Table 1.

1/ Other common "niunes f o r t h i s class of equipment are "paver" and "spreader."

24

For the jobs which were studied, i t was observed that, i n general, the faster haul and return speeds were obtained on the jobs having the longer haul distances.

A p a r t i a l breakdown of the times Involved i n various operations at the plant and at the f i n i s h e r i s shown i n Table 2.

TABLE 2

OPERATING CYCLE ELEMENTS AT THE PLANT AITO AT THE FINISHER FOR TRUCKS HAULING BITUMINOUS MIX ON BITUIGNOUS SURFACING PROJECTS

Average time Cycle element i n minutes

Time i n plant, per t r i p a. Loading time 6.3 b. Maneuvering, weighing, covering the

load, etc. 1.9

Total time i n plant, exclusive of waits and delays 6.2

Time at f i n i s h e r , per t r i p a. Discharge load 3.6 b. Maneuvering, exchanging, etc. I.5

Total time at f i n i s h e r , exclusive of waits and delays 5-3

Waits and delays, per t r i p a. At the plant l4.8 b. A l l other 3-8

Total waits and delays 18.6

The above items are largely self-explanatory. I t i s interesting to note, however, the average time required to obtain a load at the plant was 6.3 minutes or 66 percent greater than the time required (3-8 minutes) to discharge the load at the f i n i s h e r .

COMMITTEE REPORT NO. 2? - DECEMBER 195^

MAINTENANCE AND REPAIR DELAYS OF SINGLE UNIT DUMP TRUCKS HAULING MATERIALS FOR HIGHWAY BITU14IN0US SURFACING JOBS

Recent studies on single \ i n i t dxaap trucks covering a period equivalent to one truck working 2,680 10-hour s h i f t s revealed the following data re­l a t i n g t o the maintenance and repair of the tnacks.

1. Maintenance and repair delays accounted f o r nearly one-half of a l l major delays l/, excluding weather. They amo\inted to 17 percent of the available working time, or an average of I.7 hours per truck out of every 10-hour work day.

2. Maintenance and repair expense, excluding labor, amounted to an average of $7-90 per truck each scheduled 10-hour work day. This expense was equivalent to $17-50 per 1,000 ton-miles of hauling.

3. For each scheduled 10-hour work day per truck, an average of 1.75 hotirs of labor was used f o r performing the needed maintenance or repairs 2/. This was equivalent t o 3.8 man-hours of repair labor per 1,000 ton-miles of hauling.

k. There i s no correlation between duration of delay and cost of re­p a i r . For example, t i r e trouble accoianted f o r only 6 percent of a l l maintenance and repair delay timej however, replacement t i r e s and tubes alone accovuited f o r about 37 percent of the average d a i l y amount of $7-90 per truck f o r a l l repairs, excluding labor.

These studies were conducted by the Bureau of Public Roads during 1952 and 1953 on 159 single u n i t diuiip trucks hauling base and surface coiirse materials on four highway bituminous surfacing jobs.

Some of the trucks were new and two were 12 years old; the average truck was i n i t s 3rd year of use. Average struck capacity of the trucks used on each job ranged from 2.7 t o 5-2 cubic yards, without sideboards. Average load hauled varied from 4.5 t o b.2 tons but was not i n d i r e c t r e l a t i o n t o capacity. The load-capacity r a t i o varied by job from l.U t o 1.9 tons per cubic yard of struck capacity.

Table 1 shows the percentage d i s t r i b u t i o n of the major maintenance and repair delays and the average d i n ^ t i o n of each f o r the four jobs studied:

1/ Major delays are indiv i d u a l time losses 15 minutes or more i n duration. The t o t a l of a l l kinds of major delays amoimted to 30 percent of available working time, excluding weather.

2/ The truck operator's time was charged as maintenance or repair labor when he was so occiipied.

26

TABLE 1

PERCENTAGE DISTRIBUTION AND AVEEIAGE DURATION OF MAINTENANCE AND REPAIR MAJOR DELAYS

Percentage d i s t r i - Hours of working time bution of a l l time l o s t by the average l o s t i n major de- truck during each lays due t o main- i n d i v i d u a l delay

Type of delay tenance and repair occurrence Motor 21 2.9 Wrecks 18 96.4 Overhauls Ik 48.8 Clutch, transmission, drive

shaft, axle, and rear end Ik 6.7 Duznp bed and dximp mechanism 7 3.4 Tires 6 1.4 Brakes 6 2.6 Grease, change o i l , vash 6 1.2 A l l other ( f r o n t end, steering,

springs, frame, and body) 8 3.5 Total 100

COMMITTEE REPORT NO. 8 - JULY 1949 UTILIZATION OF AVAILABLE WORKING TIME OF BITUMINOUS FINISHERS l/ ON BITUMINOUS SURFACING PROJECTS IN EASTERN AND SOUTHEASTERN STATES

Equipment production studies made on bituminous fi n i s h e r s over the past 20 months on active bittimlnous surfacing jobs on r u r a l highways reveal that delays amounted t o 79 percent of the t o t a l available working time. These studies were conducted by the Production Cost Unit of the Bureau of Public Roads on eight d i f f e r e n t projects i n eastern and southeastern States and covered periods from 110 t o 215 hours on each job during the active construction season.

The bitiiminous courses which were placed by the f i n i s h e r s on these various jobs ranged from 3/4 t o 3 inches i n thickness and from 10 t o 12 feet i n width. On one of the jobs there were two crews and two f i n i s h e r s ; on three of the jobs one crew operated with one f i n i s h e r ; and on four of the jobs one crew worked with two f i n i s h e r s .

I n the l a t t e r cases where one crew worked with two f i n i s h e r s , the ma­chines operated i n adjoining lanes while the crew alternated from one f i n i s h e r t o the other every few hiuidred f e e t . Under such circmstances, one or the other of the machines i s "standby" throughout the t o t a l available working time.

Table 1 shows the percentage of 1,480 hours of t o t a l available working time as obtained from the studies. No standby time i s included.

1/ Other common names f o r t h i s class of equipment are "bituminous pavers" and "bituminous spreaders."

27

TABLE 1

DISTRIBUTION OF l,k80 HOURS TOTAL AVAILABLE WORKING TIME FOR BITUMINOUS FINISHERS ON EIGHT ACTIVE BITUMINOUS SURFACING PROJECTS ON RURAL HIGHWAYS

Percentage of t o t a l Time element available working time

Range Average

Total available working time 100 100 Major delays 28-77 57 Net available workifig time 23-72 k3 Minor delays 12-^3 22 Actual productive time 11-33 21

I n Table 1, the t o t a l available working time i s the stmi of normal d a i l y s h i f t time plus such occasional overtime as actually worked; major delays are in d i v i d u a l delays of 15 minutes or more i n duration; and minor delays are in d i v i d u a l delays of less than 15 minutes i n duration.

The extent of major delays of 15 minutes or more i n duration due t o various causes i s shown i n Table 2.

TABLE 2 CLASSIFICATION OF MAJOR DELAYS TO BITUMINOUS FINISHERS

Percentage of t o t a l available

Natvtre of Major Delay working time

Weather: r a i n , wet, cold 23 Plant shutdown due t o shortage of materials 12 Delays due t o a u x i l i a r y operations: prepara­

t i o n of subgrade, hand f i n i s h i n g of tvimouts, etc. 9

Lack of bituminous mix at f i n i s h e r U Plant repairs and adjustments 3 Finisher maintenance and repair 3 Moves on the project 2 Other _1

Total 57

The c l a s s i f i c a t i o n of minor delays i s shown i n Table 3. Although minor delays are o r d i n a r i l y j u s t a few seconds each i n duration, i t w i l l be noted i n Table 1 that they amoiint t o 22 percent of the t o t a l available working time. However, the f u l l extent of minor delays can usually be better visvialized by comparing them t o the net available working time. For example, when minor delays are expressed as a percentage of the t o t a l available working time, a job having frequent and extensive major delays, such as bad weather, tends t o show a lesser percentage of minor delays than a job having few major delays. Thus, a better basis f o r indicating the extent of minor delays i n r e l a t i o n to the production operation i s t o express them as a percentage of the net available working time.

28

For the finishers .employed on the eight jobs which were studied, the minor delays varied from 32 t o 60 percent of the net available working time with an average of 51 percent. Lack of bitminous mix accounted f o r the majority of the minor delays t o the f i n i s h e r .

TABLE 3

CLASSIFICATION OF MINOR DELAYS TO BITUMINOUS FINISHERS

Percentage of net available

Natiire of minor delay working time

Lack of bituminous mix at f i n i s h e r k3 Delays due to a u x i l i a r y operations k Finisher maintenance, repair, and adjustment 2 Personnel 1 Short moves _1

Total 51

Other minor delays due t o interference by t r a f f i c , and so on, were negligible on the Jobs studied.

An endeavor was made t o c l a s s i f y both major and minor delays i n accord­ance with t h e i r basic cause, but i n those cases where the basic cause could not be determined, the delays were c l a s s i f i e d i n accordance with the apparent cause. For example, the basic cause of a delay t o the f i n i s h e r r e s i i l t i n g from a lack of bituminous mix may have been due t o an actual shortage of hatoling units or i t may have been due to another delay elsewhere on the Job; but i f the cause of t h i s delay could not be readily determined by the observer, the delay was charged t o the apparent cause -lack of bituminous mix at the f i n i s h e r .

29

Power Shovel Grading COMMITTEE REPORT.NO. 3 - APRIL 19 * 9

UTILIZATION OF AVAIIABI£ WORKIITO TIME OF POWER SHOVEIS ON TEN ACTIVE HIGHWAY GRADING JOBS IN EASTERN AND SOUTHEASTERN STATES

Over the past l8 months, equipment production studies being conducted by the Public Roads Administration reveal that delays to power shovels on active highway grading jobs amount to 63 percent of the t o t a l available working time. "Bxese studies were made on 16 power shovels, varying i n size from 1-l/k to 2-l/2 cubic yards, on 10 d i f f e r e n t projects i n eastern and southeastern States.

Table 1 shows the percentage d i s t r i b u t i o n of l,6kO hours t o t a l a v a i l ­able working time as obtained from the studies.

TABLE 1

DISTRIBUTION OF 1,61*0 HOURS TOTAL AVAILABLE WORKING TIME FOR 16 POWER SHOVEIS ON 10 ACTIVE HIGHWAY GRADING PROJECTS

Percentage of t o t a l Time element available working time

Range Average Total available working time l / 100 100 Major delays 2/ k-dO k2 Net available woiking time 20-96 58 Minor delays 3/ 5-'<-2 V 21 Actual productive time 14-70 37 1/ The sum of ( l ) normal d a i l y s h i f t time and (2) such occasional over­

time as ac t i i f t l l y woiked. 2/ Individizal delays of I5 minutes or more i n duration. See Table 2

f o r detailed c l a s s i f i c a t i o n . 3/ Individual delays o f less than I 5 minutes i n duration. See Table 3

f o r detailed c l a s s i f i c a t i o n . kj Minor delays amotmt to 36 percent (21/58) of the net available

woriting time. There i s considerable v a r i a t i o n i n u t i l i z a t i o n of time among jobs as

indicated by the ranges of the percentages i n Table 1. One of the p r i n c i p a l items causing these variations i s weather. Tiie extent of major delays due to weather and other delays of 15 minutes or more i n duration i s shown i n Table 2.

30 TABLE 2

CIASSmCATION OF MAJOR DELAYS TO POWER SHOVELS

Nature of major delay Percentage of t o t a l available working time

Rain and wet grade 28 Shovel repairs and maintenance 10 Opening up cut, improving working s i t e 1 Blasting, rocks, roots 1 Move to new working s i t e 1 Other 1

Total 52

With one exception, a l l shovels experienced major delays due to shovel repairs and maintenance. Hc/c-ver, not all of t h i s time was l o s t i n actual repair operations; some was l o s t i n waiting f o r the needed parts to be delivered to the job a f t e r they had been ordered.

The c l a s s i f i c a t i o n of minor delays i s shown i n Table 3» Although minor delays are o r d i n a r i l y j u s t a few seconds each i n duration, i t w i l l be noted i n Table 1 that they amount to 21 percent of the t o t a l available* working time. However, the f u l l extent of minor delays can usually be better visualized by comparing them to the net available working time. For example, when minor delays are expressed as a percentage of the t o t a l available working time, a job with frequent and extensive major delays, such as bad weather, might show a proportionately less percentage of minor delays than a job with a few major delays. Thus, a better basis f o r indicating the extent of minor delays i n r e l a t i o n to the production operation i s to express them as a percentage of the net available working time.

For the l6 power shovels -vdiich were studied, the minor delays varied from 23 to 5^ percent of the net available working time with an average of 36 percent.

TABIE 3

CLASSIFICATION OF MINOR DELAYS TO POVJER SHOVELS

Nature of minor delay Percentage of net available working time

I n s u f f i c i e n t number of hauling units at shovel 12

Trimming and cleaning up woric s i t e 7 Short moves to maintain digging position k Shovel repairs and maintenance it-Waiting while haxiling u n i t maneuvers i n t o position to obtain load 3

Jtointain loading area and haul roeid 2 Handling rocks, roots, and stun^js 2 Operator and personnel delays 1 Other 1

Total 36

31

An endeavor was made to c l a s s i f y minor delays i n accordance with t h e i r basic cause, but i n those instances where the basic ca\ise could not be determined, the delays were c l a s s i f i e d i n accordance with the apparent cause. For example, the basic catise of a delay of a few seconds or perhaps a minute t o the shovel from a lack o f hauling units may have been due t o a breakdown of spreading equipment on the f i l l ; but i f t h i s f a c t could not be readily determined by the observer, the delay may have been charged to a lack of hauling units at the shovel.

Future reports w i l l deal with the hauling un i t s , operating cycle char­a c t e r i s t i c s of power shovels, and other phases of power shovel grading operations.

COMMITTEE REPORT NO. 3** - JANUARY 1958 UTILIZATION OF AVAIIABIE WORKING TIME OF POWER SHOVEIS ON

GRADING PROJECTS

Equipment production studies were conducted by the Production Cost Section of the Bureau of Public Roads during 1957 on 10 power shovels on grading projects. The shovels ranged i n size from I 5 t o 5^ cubic yards and had an average age of 2 years. I t was fo\ind that the actual productive time of these shovels was 58 percent of t o t a l avadlable working time, excluding weather shutdowns.

Table 1 shows the percentage d i s t r i b u t i o n of t o t a l available working time, as obtained from the 1957 studies. Total available working time i s the sum of ( l ) normal d a i l y s h i f t time, and (2) any overtime actually worked. Major delays are individual time losses of 15 minutes or more i n duration, while minor delays are i n d i v i d u a l time losses of less than I 5 minutes duration.

TABIE 1

PERCENTAGE DISTRIBUTION OF TOTAL AVAIIABIE WORKING TIME FOR 10 POWER SHOVEIS ON GRADING PROJECTS

Time element Percent of t o t a l available working time

Average Range 100 100 -9 0-29

-11 2-23 ~80 65-98

' -27 16-31 ' I 3 33-76

Total available working time Major delays due to weather Other major delays Net available working time Minor delays Actual productive time 1/ Minor delays amount to 3'* percent (27/80) of the net available work­

ing time. 2/ Actual productive time amounts to 58 percent (53/91) of the t o t a l

available worlcing time exclusive of weather delays.

The c l a s s i f i c a t i o n of major delays by type, as a percent of t o t a l a v a i l ­able working time, i s sho-vm i n Table 2.

32

The c l a s s i f i c a t i o n of minor delays by type i s shown i n Table 3. A l ­though minor delays are frequently only a few seconds or perhaps a minute i n duration, i t w i l l be noted i n Table 1 that they amoimt to 27 percent of the t o t a l available working time. However, the extent of minor delays can best be visualized by comparing them to the net available working time. For instance, when minor delays are expressed eis a percent of t o t a l a v a i l ­able working time, a job with an extensive amount of major delay time (such as bad weather), might show a proportionately less percent of minor delays than a job idiich had few major delays. Thus a better basis f o r indicating the r e l a t i o n of minor delays to the production operation, i s to express them as a percent of the net available working time. Net a v a i l ­able working time i s the time remaining a f t e r major delays are eliminated.

Minor delays were. I n general, c l a s s i f i e d according t o the apparent, rather than the basic, cause. Thus, i f a hauling u n i t was delayed b r i e f l y due t o t r a f f i c congestion on the f i l l , the observer at the shovel might record the delay t o the shovel merely as lack of hauling tmits at the shovel.

A previous Road Research Release (No. 3 of the Committee of Economics of Highway Construction and Maintenance, dated A p r i l 1949), covered u t i ­l i z a t i o n of working time of 16 poorer shovels on 10 grading projects. These power shovels ranged i n size from 1-1/4 t o 2-l/2 cubic yards. Analysis of t h i s e a r l i e r release indicates that actual productive time amoiuited to 51 percent (37/(100-28)) of the t o t a l available woiking time, exclusive of weather shutdowns, as con^jared w i t h the 58 percent shown i n t h i s release. The difference i s foiand p r i m a r i l y i n two categories: ( l ) minor delays caused by hauling u n i t shortages and (2) major delays caused by shovel repair and maintenance. I n connection with maintenance and repair delays i t may be noted that average age of the 10 shovels studied i n 1957 was 2 years; •vrtiereas, average age of the shovels studied i n 1947 to 1948 was 4 years.

* TABIE 2

CIASSIFICATION OF MAJOR DEIAYS

Percent of t o t a l available Type of delay working time

Rain, wet grade Shovel repair and maintenance l / A l l other Total

1/ Includes time spent waiting f o r repair parts

Average Range 9 0-29 9 1-23 2 0-4

20 2-35

33

Item No.

3 k 5

6 7 8

9 10

11

TABLE 3

CLASSIFICATION OF MUTOR DEIAYS

I ^ e of delay

Shovel operational delays Bulldozing with bucket, loosening bank and nonproductive casting

Short moves to.maintain digging position

Special handling o f oversize rock Trimming side slopes Cleanup of loading area

Haiaing u n i t delays t o shovel Lack of hauling i m i t s at shovel Hauling u n i t exchange Other hauling u n i t delays to shovel

A l l other minor delays Maintenance and repairs Late s t a r t , excess lunch time, quit early

Not otherwise c l a s s i f i e d

Percent of net available working time

Average Range

k 3 3 2

17

8 3

J . 12

1 2

8-26

2-33

2-7

Total 3^ 22-49 The average duration of a l l minor delays was U5 seconds.

COMMiraEE JEPORT NO. 33 - DECEMBER 1957 PRODUCTION RATES OF POlffiR SHOVELS ON HIGHWAY GRADING JOBS

Equipment production studies being made by the Production Cost Section of the Bureau of Public Roads indicate that poor fragmentation i n rock material handled by power shovels on highway grading cuts pro­duction more than one-half on many jobs. I n poorly fragmented material the average pay quantity per dipper load goes down. I n addition, cycle time goes up and the amount of time l o s t i n minor delays increases. Findings from studies of 35 power shovels, with rated dipper capacities from i j t o 5^ cubic yards, were used i n t h i s analysis.

Material excavated on each job studied was evaluated f o r purposes of th i s report and two general c l a s s i f i c a t i o n s were established; ( l ) w e l l fragmented material and (2) poorly fragmented material generally charac­terized by the presence of varying amounts of oversize pieces too large to pass through the dipper.

Table 1 i s a composite summary f o r a l l jobs of the data r e l a t i n g t o average minor delays, cycle time, and dipper load f o r each c l a s s i f i c a t i o n of material noted above.

3*

TABLE 1

SUMMARY OF JOB AVERAGE PERFORMANCE DATA FOR l| TO 5^ CUBIC YARD SHOVELS IN TWO CLASSIFICATIONS OF MATERIAL

Type Minor delays per hour

Cycle time per hotir

Dipper cycle time

Dipper loads per hour

Average dipper load

Produc­t i o n index

1/ (Min) (Min) (Sec) (percent

of rated capacity)

Well fragmented material 19 In 19 129 90 116

Poorly fragmented material 21 39 25 9^ 58 55

by average dipper load i n percent of rated capacity.

The average dipper load was computed on each job from dipper load counts and the corresponding cubic yards of excavation obtained from cross sections and then averaged. Cycle time data and minor delays were obtained by timing many thousands of ind i v i d u a l dipper cycles. Practical1y a l l obser­vations were made ^ i l e the shovels were loading hauling u n i t s .

Hiis analysis indicated a marfced s i m i l a r i t y i n the production index f o r shovels of d i f f e r e n t sizes i n each c l a s s i f i c a t i o n of material. However, i t sho\ad be recognized that material w e l l fragmented f o r one size shovel may not necessarily q i m l i f y f o r the same c l a s s i f i c a t i o n i f handled by a smaller shovel.

COMMITTEE REPORT HO. 5 - JUNE I9U9 DIPPER LOAD CYCLE CHARACTERISTICS OF POWER SHOVELS OK HIGHWAY GRADING JO'BS

Equipment perfoimance studies being conducted by the Production Cost Unit of the Public Roads Administration disclose that the average dipper load cycle t i n e of power shovels on highway grading jobs i s s l i g h t l y over 2k seconds, exclusive of a l l delays. The average pay yardage per dipper load i s found t o be 62 pereent of the rated capacity of the dipper on the jobs which were studied.

These findings were obtained from studies made i n recent months on 16 crawler type power shovels on 10 d i f f e r e n t projects i n eastern and south­eastern States. The shovels averaged It- t o 5 years of age and were i n good operating condition. The rated capacity of the dippers varied from 1-l/k t o 2-1/2 cubic yards.

Table 1 i s a composite suramajy f o r a l l jobs of the data relating t o the dipper cycle elements and pay yardage per dipper load.

35

TABLE 1 SUMMARY OF AVERAGE DIPPER LOAD CYCIE DATA FOR 1-1/4 TO 2-

CUBIC YARD POWER SHOVELS ON HIGHWAY GRADING JOBS 1/2

Element 1. Load 2. Swing 3. Dump 4. Return 5. Total dipper load cycle

(sum of items 1, 2, 3, and 4) l /

6. Angle of swing 7- Average pay yardage

per dipper load

l / Excludes a l l delays.

Range Average 6- 13 seconds 8.9 seconds 4- 10 seconds 5.8 seconds 2- 8 seconds 3-2 seconds 5- 9 seconds 6.3 seconds

19- 35 seconds 24.2 seconds 62-102 degrees 80 degrees

35-88 percent of 62 rated ca­pacity of dipper

percent of rated capacity of dipper

The cycle data were obtained by timing several thousand indivi d u a l cycles. P r a c t i c a l l y a l l observations were made while the shovels were loading haiiling u n i t s . The average pay yardage per dipper load was computed on esich job from dipper load counts and the corresponding cubic yards of excavation obtained from cross sections. The character of the excavation varied on each job as wel l as between jobs from "easy digging" i n l i g h t sandy materials to "hard digging" i n poorly blasted rock.

The ranges shown i n Table 1 are job averages. On several of the pro­jects the variations from day to day frequently exceeded the ranges which are shown. For example, the loading time on a pa r t i c u l a r job may have varied from 5 to 20 seconds, but only the ov e r a l l job aversige was con­sidered when l i s t i n g the entries i n Table 1.

S u f f i c i e n t studies have not yet been made to warrant analyses of the indi v i d u a l e f f e c t upon dipper cycle elements and pay yardage per dipper of such factors as condition and type of shovel, kind of material, boom angle, dipper p i t c h , height of digging face, operator efficiency, type and size of hauling u n i t , and so on.

Certain general observations of performance on the various jobs are of inte r e s t , however. For example, the smallest pay yardage i n r e l a t i o n to rated dipper capacity was observed when working against a one-foot face digging up an old portland cement concrete pavement. The longest average loading and dumping times were encountered i n material c l a s s i f i e d as "wet, s t i c k y clay." I n t h i s material i t i s inter e s t i n g to note that the pay yardage i n r e l a t i o n to rated dipper capacity was above the average f o r the remaining jobs.

As might be expected, some-vrtiat smaller pay yardage i n r e l a t i o n to rated dipper capacity and s l i g h t l y longer avereige load.ing times were experienced when working i n blasted rock. I n we l l blasted rock, however, the shovel performance with respect to cycle and pay yardage was equal to or better than the average f o r the other jobs studied.

36

COMMITTEE REPORT NO. 22 - APRIL 1953 CIASSIFICATION OF MAINTEmCE AND REPAIR DELAYS OF 15 MINUTES OR MORE

EXPERIENCED BY POWER SHOVEIS ON HI(2IWAY GRADING JOBS ANNOUNCEMENT

This report marks resumption, by the Board's Special Committee on Highway Equipment, of the series of informational reports on performance, time u t i l i z a t i o n , and costs pertaining to equip­ment enqployed on highway construction and maintenance work. The f i r s t 21 reports i n t h i s series were issiied dviring the period March I9U9 t o January I95I by the Board's former Com­mittee on Economic of High^reiy Construction and Maintenance Methods.

Maintenance and repair delays of 15 minutes or more each experienced by power shovels on active highway grading jobs account f o r a t o t a l down time of about 1.2 hours out of every 10-hour work day. l/ On some jobs down time due to such causes was double t h i s amount.

The magnitude of these losses was determined from studies conducted by the Bureau of Public Roads on kl shovels i n use on 31 projects during a work period of 4,500 hoixrs. 2/ On the basis of 276 maintenance and repair delays which were observed, one such time loss occurs every 16 hours and i s about 115 minutes i n duration.

Table 1 shows ( l ) the p r i n c i p a l types of maintenance and repair delays encountered, (2) the percentage that each i s of the t o t a l maintenance and repair delay time, and (3) the average duration of indivldvial delays.

1/ Weather shut doims are not considered part of the work day. 2/ Individual studies cover a calendar period of about three weeks

during the active construction season. This f i e l d study program has been i n e f f e c t since 19^7.

TABLE 1 PERCEI TAGE DISTRIBUTION MID AVERAGE DURATION OF 276 MAINTENAJICE AND

REPAIR DELAYS OF 15 MIN. AITO OVER EXPERIENCED BY POVJER SHOVEIS ON HIGir.JAY GRADING

Total mainte- Average dura-Type of delay nance and repair t i o n of each

delay time delay (percent) (Min)

1. Poorer transmission system, clutches, brakes, gears, drums, controls, etc. except cable hO 111

2. Boom and dipper assembly, except cable 26 117

3- Wait f o r repair parts 17 5IO h. Car body and crawler assembly 6 87 5. Motor 5 94 6. Cable k 57 7. Other 2 3I

Total 100 115

37

On many jobs "hard digging" was encountered i n ledge rock, shale, and blasted rock. Such material obviously contributes to the l i k e l i h o o d of greater frequency of maintenance and repair delays t o the power shovel. I n some instances, however, opportunities exist with respect to minimizing the ef f e c t of poor digging conditions. Evidence of t h i s f a c t i s that some power shovels having the least delays are those which worked i n rock which had been well blasted.

The analysis also revealed that shut downs due t o weather and down time due to maintenance and repair -vrere both at a maximum on those jobs upon which studies were made during the winter months.

Other important factors which aff e c t maintenance and repair delays but which are d i f f i c u l t to evaluate s p e c i f i c a l l y on a uniform basis, are the carefulness and ef f i c i e n c y of the operator, condition of equipment, sched­uled and nonscheduled repair and maintenance practices, and so on.

COI-IMITTEE REPORT NO. 21 - JANUARY 1951 PERFORMANCE CHARACTERISTICS AND UTILIZATION OF AVAILABLE WORKING TIME

OF ROCK THICKS ON POVIER SHOVEL HIC3IWAY GRADING OPERATIONS

Hauling unit studies made during the past three years on off-the-high-\my trucks equipped with rear dunip, heavy duty, chute type bodies and work­ing with power shovels on active r u r a l highway grading projects reveal that t h i s class of equipment, hereinafter termed "rock trucks," i s u t i ­l i z e d productively k3 percent of the t o t a l available working time. 'Die pay load averages 78 percent of struck capacity; haul and return speeds average 7'25 miles per hour; and the t o t a l time each truck spends i n load­ing, dimrping, and turning averages k.6 minutes each round t r i p , exlusive of a l l delays.

These studies were conducted by the Production Cost Unit of the Bureau of Public Roads. Hie data presented i n t h i s report represent a composite svmmary of the observations made on t h i s p a r t i c u l a r class of hauling u n i t under a var i e t y of excavating, hauling, and dumping conditions and manage­ment practices. No endeavor has been made to present selected data f o r purposes of enabling comparisons to be made with other types or classes of equipment.

More than 2,200 truck hours of operation are represented by these studies on seven active highway grading projects i n eastern, central, and western States. The power shovels which were employed averaged 2.0 cubic yards i n size, ranging from 1^ to 2|- cubic yards. Over 6,000 loads were hauled during the period by 30 rock trucks which ranged i n size from 9.7 to 13*1 cubic yards struck capeicity. Materials hauled v/ere, f o r the most part, blasted shale and limestone, although some clay was encountered on two projects.

T^ble 1 shows the d i s t r i b u t i o n of the t o t a l available working time as obtained from the studies.

38

TABLE 1 DISTRIBUTION OF TOTAL AVAILABLE WORKING TIME FOR ROCK TRUCKS

Percentage of t o t a l Time element available woricing time

Range Average Total available working time 100 100 Major delays 38-li-5 h2 Net available working time 55-62 58 Minor delays 12-23 15 Actual productive time 39- 6 lj-3

I n Table 1, the t o t a l available woricing time i s the sum of noimal d a i l y s h i f t time plus such occasional overtime as act\ially worked; major delays etre i n d i v i d u a l delays of 15 minutes or more i n duration; minor delays are individ u a l delays of less than 15 minutes i n duration; and actual productive time i s time spent by the truck i n loading, hauling, dumping, returning, and exchanging, exclusive of a l l delays.

The extent of major delays of 15 minutes or more i n duration due t o various causes i s shown i n Table 2.

TABLE 2

CLASSIFICATION OF MAJOR DELAYS TO ROCK TRUCKS

Nature of major delay Percentage of t o t a l =^ available working time

Weather - r a i n and wet grade 21 Maintenance and repair of truck 7 Standby i d l e : Available, but pariced and not being used 7 Shovel delays k Blasting 2 Other 1

Total k2

The c l a s s i f i c a t i o n of minor delays i s shown i n Table 3. Minor delays are o r d i n a r i l y only a few seconds each i n duration, and i n Table 1 i t w i l l be noted they amount t o 15 percent of the t o t a l available working time. However, the f u l l extent of minor delays can usually be better vi s i i a l i z e d by comparing them to the net available working time. For example, when minor delays &re expressed as a percentage of the t o t a l available working time, a job having frequent and extensive major delays, such as bad weather, tends t o show a lesser percentage of minor delays than a job having a few major delays. Thus, a better basis f o r indicating the extent of minor delays i n relation to the production operation i s to express them as a percentage of the net available working time.

On the seven jobs which employed t h i s type of equipment, minor delays varied from 9 to 37 percent of the net available working time, with an average of 26 percent.

39

TABLE 3

CLASSIFICATION OF MINOR DEIAYS TO ROCK TRUCKS

Nature of minor delay

Wait at the shovel Maintenance and repair of truck Haul road maintenance and repair Truck operator Other

Total

Percentage of net ava i l -able working time

21 1 1 1 2

26

Table 4- i s a composite summary of job average data r e l a t i n g to the hauling u n i t cycle elements and perfoimance data. A l l delays have been excluded from the time elements l i s t e d .

TABIE 4

SUMMARY OF AVERAGE ROUND TRIP CYCLE DATA FOR ROCK TRUCKS

Element Range Average

1. Load 1.3-•3.4 minutes 2.4 minutes 2. Dump and turn 0.8--2.0 minutes 1.4 minutes 3. Turn at shovel 0.1--0.7 minutes 0.5 minute 4. Exchange 0.0-•0.5 minute ' 0.3 minute 5- Total time constant

(svim of items 1, 2, 3, 4.6 and 4) 2.9--6.1 minutes 4.6 minutes

6. Haul distance 121-•3,320 feet 1,494 feet 7. Haul speed, loaded 3.1-•15-3 miles/hr 7.2 miles/hr 8. Return speed, empty 3.4--11.6 miles/hr 7-3 miles/hr 9. Average pay yardage

65- 78 per truck load 65- -89 percent of 78 percent of struck capacity

struck capacity

Ranges shown i n Table 4 are job averages. Dally variations, however, frequently exceeded the ranges sho\m. For example, the loading time on a p a r t i c u l a r job may have varied from 2.5 to 4.0 minutes, but only over­a l l job average was considered when l i s t i n g the entries i n Table 4. Yard­age data were obtained from load counts and the corresponding cubic yards of excavation obtained from cross sections during each study.

S u f f i c i e n t studies have not yet been made on t h i s p a r t i c u l a r type of u n i t t o warrant appraisal o f the i n d i v i d u a l e f f e c t upon perfoimance char­a c t e r i s t i c s of such factors as condition of the u n i t , condition of the haul road, gradient, and operator e f f i c i e n c y .

1*0

COMMITTEE REPORT NO. 31 - JUNE 1956 GUIDE TO HAULING UNIT NEEDS ON POWER SHOVEL GRADING JOBS

Equipment production studies conducted by the Production Cost Unit of the Bureau of Public Roads on power shovel grading jobs reveal certain general relationships between length of haul, capacity of an end dump truck f l e e t i n terms of shovel dippers, and percent of shovel time l o s t i n waiting on trucks. Hile i s i l l u s t r a t e d by Figure 1.

Further analysis with respect to time l o s t by the shovel i n waiting on trucks and to time l o s t by the trucks i n waiting at the shovel indicates the existence of an empirical relationship. When expressed as a percent of the working time ( t o t a l time less a l l delays of 15 minutes or more i n diuration) the sum of these two time losses normally adds up to 29*. The average f o r a l l jobs studied showed that 12 percent of shovel time was l o s t i n vreiiting on trucks and that 17 percent of truck time was l o s t i n waits at the shovel. The extremes f o r shovel time losses (while waiting on trucks) ranged from k to 25 percent while the corresponding extremes f o r truck time losses (while waiting at the shovel) ranged from 25 to 4 percent.

Figure 1 i s based on observations of shovels from 3/^- to 2-l /2-cubic yard rated capacity, end dump trucks of h to ik cubic yards struck capac­i t y , and average haul road conditions. Seldom,if ever, w i l l a p a r t i c u l a r job have a l l the characteristics of an average job. Effects of such var­iables as excessive greides, mechanical condition of equipment, material c l a s s i f i c a t i o n , and others must be given due consideration.

When easy digging conditions are encountered on short hauls a notice­able increase occurs i n the requirement f o r hauling u n i t s . For any given f l e e t , t h i s s i t i i a t i o n i s reflected i n increased waits by the shovel f o r trucks. Daished lines indicate values f o r easy digging on hauls of 500, 1,000, and 1,500 feet. At 2,000 feet and above easy digging did not s i g n i f i c a n t l y a f f e c t normal values.

With respect to the dipper capacity of the f l e e t , job experience i s , of course, the f i n a l c r i t e r i o n . However, a general indication of t y p i c a l dipper capacities of two common sizes of end dump trucks operating with four sizes of shovels i s shown i n Table 1.

TABLE 1

AVERAGE NUMBER OF SHOVEL DIPPERS REQUIRED TO LOAD END DUMP TRUCKS

Shovel Struck capacity of trucks size 10 cubic yards 5^ cubic yards

cu. yd. 3A - 7.0 Li l i 7.2 3.8

5.5 2.9 2 i k.2 2.3

hi

I n Figure 1 an indication of TOits by the shovel f o r trucks may be de-temined with c e r t a i n given conditions. As an exaniple, assume that 10-cubic yard end dump trucks are being used with a 2-cubic yard shovel. F l e e t s of 3, k, 5, or 6 trucks have c a p a c i t i e s of 16.5, 22, 27.5, and 33 dippers, respectively, as determined from Table 1. With a 3,000 foot haul three trucks w i l l keep the shovel waiting about 30 percent of the working time, four trucks would reduce t h i s to about 16 percent, f i v e trucks would reduce the waits s t i l l further to about 8 peixient, and s i x trucks indicate an amount below 5 percent. Further, by application of the empirical r e l a t i o n previously cited, i t would be expected that three trucks would loose no time i n waits a t the shovel, four trucks would lose about 13 percent of t h e i r time i n waits, f i v e trucks about 21 percent, and s i x trucks about 2k percent.

g « 20

Length of haul, feet

15 20 25 30 35 Capacity of end chn^ truck fleet In shovel dippers

1 5

Figure 1. Relation of truck f l e e t capacity to shovel delays for varying lengths of h a u l .

h2

Scraper Grading Crawler Tractor Drawn Units

COMMITTEE REPORT NO. 10 - SEPTEMBER 19* 9 UTILIZATION OF AVAIIABLE WORKING TIME OF CRAWLER TRACTOR-DRAWN SCRAPER

UNITS ON CE ADING OPERATIONS IN EASTERN AND SOUTHERN STATES

Equipment production studies made during the past two years on crawler tractor-drawn scraper units working on active r u r a l highway grading jobs reveal that delays amount to hi percent of the t o t a l available working time. These studies were conducted by the Production Cost Unit of the Bureau of Public Roads, and the data presented i n t h i s report represent a composite summary of the obsei^rations made vinder a var i e t y of job con­ditions and management p r a c t i c e s . No endeavor has been made to present selected data for purposes of enabling comparisons of performance to be made with other types or cla s s e s of equipment.

Table 1 shows the percentage d i s t r i b u t i o n of 3>900 hours of t o t a l available working time as obtained from studies made on hi vinits on 11 different projects i n seven eastern and southern States. The s i z e of the crawler t r a c t o r s ranged from 70 to 150 drawbar horsepower and generally varied i n proportion to the s i z e of the scrapers which ranged from 8 to 19 cubic yards struck capacity.

TABLE 1

DISTRIBUTION OF 3,900 HOURS TOTAL AVAILABLE WORKING TIME FOR kl CRAWLER TRACTOR-DRAWN SCRAPER UNITS ON 11 ACTIVE GRADING PROJECTS

ON RURAL HIGffir/AYS

Percentage of t o t a l Time element available working time

Range Average

Total available working time 100 100 Major delays lk-66 37 Net available working time 3I+-86 63 Minor delays 3-12 k , Actual productive time 31-78 59

I n Table 1, the t o t a l available working time i s the s^m of normal d a i l y s h i f t time plus such occasional overtime as a c t u a l l y worked; major ' delays are individual delays of 15 minutes or more i n duration; and minor delays are individual delays of l e s s than 15 minutes i n duration.

The extent of major delays of 15 minutes or more i n duration due to various causes i s shown i n Table 2.

h3

TABLE 2

CLASSIFICATION OF MAJOR DELAYS TO CRAWLER TRACTOR-HRAWN SCRAPER UNITS

Percentage of t o t a l available

Natvire of major delay working time

Weather: r a i n , cold, wet grade 25 Maintenance and repair of vualt 8 Waiting on a\axiliary operations: clearing,

placing pipe, r o l l i n g on f i l l , e t c , 2 Other _2

Total 37

Of a l l the major delays due to weather, approximately one-third was caused by wet grade.

The c l a s s i f i c a t i o n of minor delays i s shown i n Table 3» Minor delays are o r d i n a r i l y only a few seconds each i n duration, and i n Table 1 i t w i l l be noted they amount to h percent of the t o t a l available working time. However, the f u l l extent of minor delays can usually be better v i s u a l i z e d by comparing them to the net available working time. For example, when minor delays are ejqjressed as a percentage of the t o t a l available working time, a job having frequent and extensive major delays, such as bad weather, tends to show a l e s s e r percentage of minor delays than a job having a few major delays. Thus, a better basis for indicating the extent of minor delays i n r e l a t i o n to the production operation i s to express them as a percentage of the net available working time.

On the 11 jobs which were studied, minor delays varied from k to l6 percent of the net available working time with an average of 6 percent.

TABLE 3

CLASSIFICATION OF MINOR DELAYS TO CRAWLER TRACTOR-DRAWN SCRAPER UNITS

Percentage of net available

Nature of minor delay working time

Maintenance and repair of unit 2 Awaiting pusher 1 Maintaining haul road 1 Personnel 1 Other 1

Total 6

COMMITTEE REPORT NO. 12 - OCTOBER 19 9 OPERATING CYCLE OF CRAWLER TRACTOR-DRAWN SCRAPER UNITS ON HIGHWAY

GKADING OPEEiATIONS IN EASTERN AND SOUTHERN STATES

Equipment production studies made during the past two years on crawler tractor-drawn scraper units working on active r u r a l highway grading jobs show that the t o t a l time each scraper unit spends i n loading, dmnping, and turning averages 2.85 minutes each round t r i p . The average t r a v e l speed while haxiling and returning was approximately 335 feet per minute. These studies were conducted by the Production Cost Unit of the Bureau of Public Roads, and the data presented i n t h i s report represent a com­posite siimmary of observations made under a va r i e t y of job conditions and management p r a c t i c e s . No endeavor has been made to present selected data for purposes of enabling comparisons of performance to be made with other types or c l a s s e s of equipment under i d e n t i c a l operating conditions.

Forty-one tinits working on 11 different projects were observed for a t o t a l of 3 900 hours of t o t a l available working time during which approxi­mately 22,000 loads of material were moved. The scrapers ranged i n s i z e from 8 to 19 cubic yards struck capacity and were pulled by t r a c t o r s having 70 to 150 drawbar horsepower.

Table 1 i s a composite summary for a l l jobs of the data r e l a t i n g to the scraper cycle elements and the pay yardage per scraper load.

TABLE 1

SUMMARY OF AVERAGE ROUND TRIP CYCLE DATA FOR 8 TO 19 CUBIC YARD CRAWLER TRACTOR-DRAWN SCRAPER UNITS ON RURAL HIGHWAY GRADING JOBS

Element

Load Dump and twm at f i l l Turn i n cut Total time constant

(sum of items 1, 2, and 3)

Ha\il distance Haul speed, loaded Return speed,empty Pay yardage per load

Range

1.1-2.9 minutes O.U-1.3 minutes 0.3-0.7 minutes

Average

1.68 minutes .75 minute .k2 minute

I.9-U.2 minutes 130-1,300 feet I65-U7O feet/minute 230-1 80 feet/minute 56-106 percent of struck

capacity of scraper

2.85 minutes 536 feet 322 feet/minute 314-5 feet/minute

79 percent of struck capacity of scraper

Pusher t r a c t o r s were used to a s s i s t i n the loading operation i n about 60 percent of the cases throughout the period of observation. A l l delays have been excluded from the time constant elements (items 1, 2, 3> and k) l i s t e d i n Table 1. The haul distance, item 5, i s the longitudinal distance traveled from the point the scraper gate i s closed a f t e r the load i s obtained to the point where the scraper gate i s opened to discharge the load.

The cycle data were obtained by timing several thousand individual round t r i p s . The average pay yardage per scraper load was computed on each job from load counts and the corresponding cubic yards of excavation obtained from cross sections. Character of excavation varied on each job as well as between jobs from "easy digging" i n comparatively l i g h t mate­r i a l to "hard digging" i n blasted shale rock.

h5

The ranges i n Table 1 are job averages. On several of the projects the variations from day to day frequently exceeded the ranges which are shown. For example, the loading time on a p a r t i c u l a r job may have varied from 0.7 to 3.1 minutes, but only the o v e r - a l l job average was considered when l i s t i n g the entries i n Table 1.

I n general, the smaller scrapers were observed to have a s l i g h t l y smaller time constant, and s l i g h t l y higher haul and return speeds than the larger u n i t s . Also, for the units studied, a s l i g h t l y larger pay load i n r e l a t i o n to the si z e of the unit was obtained by the smaller u n i t s .

The use of pushers materially improved the performance of the larger scraper units by decreasing the loading time and loading distance, and by increasing the pay load. For the smaller scraper units, the pushers re­duced the loading time and loading distance, but did not materially a f f e c t the pay load. These observations are made sole l y on the basis of the observed f i e l d conditions. No studies have thus f a r been made for the purpose of comparing performance with and without pusher assistance under otherwise i d e n t i c a l operating conditions.

Future reports on these and other factors a f f e c t i n g scraper performance, such as si z e and type of unit, kind of material, grades, ground conditions, operator e f f i c i e n c y , and so on, w i l l be issued at such time as a s u f f i c i e n t number of studies have been made to afford more positive indication of the extent of these v a r i a t i o n s .

COMMITTEE REPORT NO. 2k - JUNE 1953 LENGTH OF HAUL FOR CRAWLER TRACTOR AND SCRAPER COMBINATIONS

ON HIGHWAY GRADING JOBS

Studies of crawler tractor and scraper combinations on highway grading jobs reveal that the observed t r a v e l distance, or apparent haul, from end of loading to s t a r t of dumping averages 565 feet. These studies were made over the past 5 years by the Production Cost Unit of the Bureau of Public Roads on 23 highway grading jobs selected at random. Over 9,000 observa­tions were made on 71 crawler t r a c t o r and scraper combinations ranging i n siz e from 6 to 28 cubic yard struck capacity.

Figure 1 shows percentage d i s t r i b u t i o n of t o t a l loads by various inc r e ­ments of apparent haul. The nvimber at the top of each bar i s the percent­age value. The longest apparent haul observed was a single load for 3,600 feet.

To determine the relationship, i f any, between size of scraper and apparent haul, the observations were arrayed into fovir groups, from small s i z e scrapers to large s i z e scrapers. Each grourp covered approximately one fourth of a l l loads. The maximum difference i n the average apparent haul between any two of these groups was 20 f e e t .

On the jobs studied, the "true haul" or distance along a direct path from midpoint of loading to midpoint of dumping averaged 6kO feet. I n computing true haul, adjustment was made for the fact that some loads were hauled over circuitous routes.

I 6

Percent of t o t a l observed loads

25

20

15

10

0

16

22

21

23

16

10

5

0 200 liOO 600 800 1000 1200 to to to to to to to 199 399 599 799 999 1199 1399

Length of apparent haul i n feet

ll»00 i6oo to emd

1599 over

Figure 1. Percentage d i s t r i b u t i o n of t o t a l observed loads of crawler t r a c t o r and scraper combinations by various apparent haul distances.

COMMITTEE REPORT NO. 35 - MARCH 1958 HOURLY COST OF LARGE CRAWLER TRACTORS

Recent cost studies on seven highway construction projects made by the Bureau of Public Roads included 27 large crawler t r a c t o r s ( l l O to ll+O horsepower) among the equipment studied. The detailed costs for each t r a c t o r are shown i n Table 1. None of the costs include allowances for cen t r a l o f f i c e administrative overhead or general business taxes.

These studies were made i n f i v e States and included equipment owned by six contractors. Approximately 10,000 working hours were involved. A working hour i s defined as the time remaining a f t e r excluding individual delays of 15 minutes or over.

A l l expenses incurred during the period of a p a r t i c u l a r study were charged d i r e c t l y to an individual unit of equipment wherever possible. Some costs, such as "Shop overhead" were prorated. Some of the more common expenses i n t h i s l a t t e r category are depreciation of shop buildings, i n t e r e s t on investment i n land, tools, miscellaneous supplies, and service equipment used exclusively at the shop.

Labor costs include wages and other labor-related expenses such as s o c i a l security, l i a b i l i t y insurance, uneniployment compensation, and vacation and sic k leave. These other labor-related expenses amounted to about 28 cents per working hour of the t r a c t o r .

I n the labor category i t was observed that for each working hour of the equipment, the operator used 1.07 hours of h i s time. I n addition to t h i s amount, the operator, mechanics, and service la^borers worked 0.26 man-hour for each working hour of the unit i n performing maintenance and repair work.

TABLE 1

COST PER WORKIHG HOUR OF 27 LARGE CRAWLER TRACTORS BY SELECTED ELEMENTS OF COST

Pri n c i p a l use Years of age

Working hours -percent of t o t a l hours 1/

Gallons of f u e l

per hour

COST

Pri n c i p a l use Years of age

Working hours -percent of t o t a l hours 1/

Gallons of f u e l

per hour

Fuel, o i l , aod

grease

Repair parts and

repair service

Direct taxes and

insur­ance

Shop over­head

Expense of other

equipment for

servicing

Depre­ciation

and interest

3/

Sub­t o t a l

Labor Pr i n c i p a l use Years of age

Working hours -percent of t o t a l hours 1/

Gallons of f u e l

per hour

Fuel, o i l , aod

grease

Repair parts and

repair service

Direct taxes and

insur­ance

Shop over­head

Expense of other

equipment for

servicing

Depre­ciation

and interest

3/

Sub­t o t a l Mainte­

nance & repair

Opera­tio n

Total

Pusher on scraper grading 0 96 2/ 10.2 $1.85 $ 0.18 $0.27 $0.57 $0.10 $l*.ilf $7.11 $0.21 $3.32 $10.61* Pusher on scraper grading 1 82 1*.7 0.86 1.51 y 0.33 0.31 3.72 6.73 0.38 2.06 9.17 Bulldozer 1 70 4.2 0.79 1.30 0.30 0.32 3.38 6.09 0.36 2.27 8.72 Bulldozer 1 7^ 1*.6 0.73 0.15 y 0.22 0.19 3.21 1*.50 0.38 2.07 6.95 Pusher on scraper grading 1 53 3.1* 0.68 0.05 0.27 1.1*5 l*.95 7.1t0 1.59 3.32 12.31

Pusher on scraper grading 1 91 1*.9 0.94 0.06 0.18 0.10 0.26 2.65 l*.19 0.16 3.1*9 7.81* Pusher on scraper grading 1 88 5-5 1.05 0.08 0.20 0.10 0.23 2.71* h.ko 0.19 3.36 7.95 P u l l scraper unit 1 85 6.1* l . l i * O.lU 0.19 O.U 0.16 2.80 i*.5l* 0.25 3.56 8.35 Feeding gravel to crusher 2 82 6.2 1-59 1.25 0.23 0.03 . 2.10 5.20 0.66 3.10 8.96 Bulldozer 3 93 5.9 1.22 10.97 0.16 0.43 0.99 1.1*3 15.20 1.1(0 3.53 20.13

Feeding gravel to crusher k 73 6.5 1.81 l . l l * 0.31 O.oi* _ 0.87 1*.17 0.53 3.20 7.90 Pusher on scraper grading k 51* 6.9 1.16 1.81 O.ll* 5.73 0.1*1 1.81* 11.09 0.93 3.76 15.78 Pulling scraper unit 5 82 5.3 1.07 l*.93 0.27 0.1*3 0.13 0.65 7.1*8 0.91 3.62 12.01 Feeding blasted rock to crusher 5 71* 3.5 0.73 3.82 0.10 0.58 - 0.89 6.12 1.78 3.32 11.22 Pulling scraper unit 5 99 6.0 1.23 o.Uo o.oi* 0.37 0.16 0.50 2.70 0.1*8 3.06 6.21*

Bulldozer 6 73 5.3 1.20 6.1*1 0.11 0.29 1.56 0.63 10.20 I.7I* 3.51* 15.1*8 Pulling scraper unit 6 87 5.9 1.17 15.59 0.10 0.55 0.61* 0.1*7 18.52 0.89 3.52 22.93 Pulling scraper unit 6 78 5.9 1.23 15.88 0.10 0.57 1.20 o.^k 19.52 1.75 3.1*8 21*.75 Bulldozer 7 85 i*.6 0.83 0.35 0.11 2.77 0.15 0.55 i*.76 0.31* 3.68 8.78 Pulling scraper unit 8 87 5.2 1.06 0.26 0.23 0.30 0.13 1.28 3.26 0.1*9 3.35 7.10

Pulling scraper unit 8 89 5.5 1.19 l.Ol* o.oi* 0.36 0.32 1.16 l * . l l 0.87 3.12 8.10 Pulling scraper unit 8 9k 5.7 1.28 1.71 o.oi* 0.40 0.25 1.11 1*.79 l.Ol* 3.09 8.92 Pulling scraper unit 8 67 5.1* 0.92 0.21* 0.12 2.91 0.15 0.38 l*.72 0.50 3.62 8.81* Pulling scraper unit 8 28 6.0 1.02 0.11 0.11 5.77 o.ll* 0.93 8.08 0.36 3.1*5 11.89 Bulldozer 8 71 l * . i 0.75 0.16 0.13 2.70 0.20 0.1*5 i*.39 0.1*2 4.18 8.99

Feeding blasted rock to crusher 9 67 3-5 0.73 8.11* 0.09 0.37 0.97 0.32 10.62 2.50 3.19 16.31 Pulling scraper unit 9 68 5.8 0.99 0.1*2 0.12 3.01* 0.15 0.32 5.04 0.35 3.62 9.01

2/ Equipped with torque-convertor. 3/ Based on the declining balance method of depreciation to zero salvage over a 15,000 hour period of job retention. Interest computed at 6 percent of

the cost new l e s s depreciation. h/ Could not be separated from central office administrative overhead which has been omitted from t h i s table.

ha

Scraper Grading Rubber Tired Tractor Drawn Units

C0M^tIT^EE REPORT NO. 11 - SEPTEMBER 19^9 UTILIZATION OF AVAIIABIE WORKING TIME OF RUBBER TIRED TRACTOR-DRAWN

SCRAPER UNIIS ON HIGHWAY GRADING PROJECTS II-I SOUTHERN STATES

Studies conducted during the past l6 months on active r u r a l highway grading projects reveal that 72 percent of the totsLL available worfcing time of rubber t i r e d tractor-drawn scraper units i s l o s t i n delays. These studies were conducted by the Production Cost Unit of the Bureau of Public Roads. Hie data represent a composite summary of a v a r i e t y of job conditions and management p r a c t i c e s . No endeavor has been made to present selected data f o r purposes of enabling comparisons of perfonnances to be made with other types or cl a s s e s of equipment.

The studies cover operations of 19 scraper units during 2,66o hours of t o t a l available woriting time on s i x jobs i n three southern States. Uie scrapers ranged from 8 to 13 cubic yards struck capacity and were pulled by 2- and l»--vdieel rubber t i r e d t r a c t o r s ranging i n s i z e from 110 to 135 drawbar horsepower. Pushers ^rere used with the xmits on a l l s i x pr o j e c t s .

Table 1 shows the di s t r i b u t i o n of the combined t o t a l available working time f o r the 19 scraper i m i t s .

TABLE 1

DISTRIBUTION OF 2,660 HOURS TOTAL AVAILABIE WORKING TIME FOR 19 RUBBER TIRED TRACTOR-DRAWN SCRAPER UNITS ON SIX ACTIVE RURAL

HIGHWAY GRADING PROJECTS Percentage of t o t a l available

Time element woriting time Range Average

Total available woriting time 100 100 Major delays 28-85 65 Net available working time 15-72 35 Minor delays 3-12 7 Actual productive time 12-6l 28

In Table 1, the t o t a l available working time i s the sum of normal d a i l y s h i f t time plus such occasionca overtime as a c t u a l l y worked; major delays are in d i v i d u a l delays of I 5 minutes or more i n duration; and minor delays are Individual delays of l e s s than 15 minutes i n duration.

The extent of major delays of 15 minutes or more i n duration due to various causes i s shown i n Table 2.

^9

TA£IE 2

CIASSIFICATION OF MAJOR DELAYS TO RUBBER TIRED TRACTOR-DRAW SCRAPER UNITS

Nature of major delay

Weather: Rain, cold, wet grade Open up cuts, trimming, e t c . ^^aintenance and repair of unit Lack of operators Other

Total

Percentage of t o t a l available working time

k 3 3 1

On some of the jobs studied, the r a i n f a l l was much greater than normal. This accounts for a large portion of the delay due to weather. I t was also observed that wet grade was responsible for 6o percent of a l l major delays due to weather.

The c l a s s i f i c a t i o n of minor delays i s shown i n Table 3. Individual minor delays are o r d i n a r i l y only a few seconds each i n duration and con­s t i t u t e seven percent of the t o t a l available working time as shown i n Table 1. However, t h e i r f u l l extent can usually be better v i s u a l i z e d by comparing them to the net available working time. For example, when minor delays are expressed as a percentage of the t o t a l available working time, a job having frequent and extensive major delays, such as bad weather, tends to show a l e s s e r percentage of minor delays than a job having a few major delays. Thus, a better basis for indicating the extent of minor delays i n r e l a t i o n to the production operation i s to express them as a percentage of the net available working time.

Minor delays constitute almost one-fifth of the net available working time for the s i x jobs combined and varied on individual projects from l6 to 26 percent.

TABLE 3

CLASSIFICATION OF MINOR DELAYS TO RUBBER TIRED TRACTOR-DRAWN SCRAPER UNITS

Nature of minor delay

A^7aiting pusher Maintenance and repair of unit Maintaining haul road Personal Contractor's t r a f f i c Other

Total

Percentage of net a v a i l -able ^forking time

12 2 1 1 1

_2 19

50 COMMITTEE REPORT NO. 13 - OCTOBER 19^9

OPERATING CYCLE OF RUBBER TIRED TRACTOR-DRAWN SCRAPER UNITS ON HIGHWAY GRADING OPERATIONS IN EASTERN AND SOUTHERN STATES

Equipment production studies made during the past two years on rubber t i r e d tractor-drawn scraper units working on active r u r a l highway grading jobs show that the t o t a l time each scraper unit spends i n loading, dumping, and turning, averages 2.2 minutes each round t r i p . The average t r a v e l speed •vrtiile hauling and returning was approximately 695 feet per minute. These studies vrere conducted by the Production Cost Unit of the Bureau of Public Roads, and the data presented i n t h i s report represent a composite summary of the observations made under a v a r i e t y of job conditions and management pr a c t i c e s . No endeavor has been made to present selected data f o r pur­poses of enabling comparisons of perfoimance to be made with other types or c l a s s e s of equipment under i d e n t i c a l operating conditions.

Nineteen units working on 6 d i f f e r e n t projects were observed for a t o t a l of 2,660 hours of t o t a l available vrorking time during -vdiich time approxi­mately 9,200 loads of material were moved. The scrapers ranged i n s i z e from 8 to I3 cubic yards of struck capacity and were pulled by 2- and k-wheel rubber t i r e d t r a c t o r s having 110 to 135 drawbar horsepower.

Table 1 i s a composite summary for a l l jobs of the data r e l a t i n g to the scraper cycle elements and the pay yardage per scraper load.

TABIE 1

SUMMARY OF AVERAGE ROUND TRIP CYCLE DATA FOR 8 TO 13 CUBIC YARD RUBBER TIRED TRACTOR-DRAWN SCRAPER UIHTS ON HIGHWAY GRADING JOBS

Element

1. Load 2. Dump and turn at f i l l 3. Turn i n cut k. Total time constant

(sum of items 1, 2, and 3)

5. Haul distance 6. Haul speed, loaded 7. Return speed, empty 8. Pay yardage per load

Range

0.9-2.2 minutes 0.4-0.7 minute 0.2-O.h minute

1.8-3.3 minutes k20-l,890 feet 1^65-l,100 feet/minute 370-1,200 feet/minute 68-9^1- percent of struck

capacity of scraper

Average

1.36 minutes 0.56 minute 0.31 minute

2.23 minutes 873 feet 676 feet/minute 71'4- feet/minute Ok- percent of

struck capacity I of scraper

Pusher or p u l l (snatch) tractors were used to a s s i s t i n the loading operation i n more than 98 percent of the cases throughout the period of observation. A l l delays have been excluded from the time constant e l e ­ments (items 1, 2, 3, and k) l i s t e d i n Table 1. The haul distance, item 5, i s the longitudinal distance traveled from the point the scraper gate i s closed a f t e r the load i s obtained to the point where the scraper gate i s opened to discharge the load.

The cycle data were obtained by timing several thousand individual round t r i p s . Average pay yardage per scraper load was computed on each job from load counts and the corresponding cubic yards of excavation ob­tained from cross sections. The character of excavation varied on each job as well as between jobs from "easy digging" i n loose, l i g h t , bulky

51 materials to "hard digging" i n compacted c l a y or rocky materials.

The ranges i n Table 1 are job averages. On several of the projects the variations from day to day frequently exceeded the ranges which are shown. For example, the loading time on a p a r t i c u l a r job may have varied from 0,k to 2.8 minutes, but only the overall job average was considered when l i s t i n g the entries i n Table 1.

S u f f i c i e n t studies have not yet been made to warrant analyses of the individual e f f e c t upon scraper cycle elements and pay yemiage per scraper load of such factors as indlvidiiaJ. s i z e and type of unit, kind of material, grades, ground conditions, operator e f f i c i e n c y , and so on.

Certain general observations of performance on the various jobs are of i n t e r e s t , however. As might be expected, the smaller units sho-vred a s l i g h t advantage over the l a r g e r vmits with respect to the extent of time constant. Also, for the units studied, a s l i g h t l y l a r g e r pay load i n r e l a t i o n to the s i z e of the \anit was obtained for the smaller u n i t s . On the other hand, the haul and return speeds for the l a r g e r imits were somewhat f a s t e r . The variations among these factors for various s i z e s of units ^rere within rather narrow ranges. Future reports on these matters v r i U be issued at such time as a s u f f i c i e n t nmber of studies are made to afford more positive indication of the extent of these var­i a t i o n s .

COMMITTEE REPORT NO. l6 - FEBRUARY 1950 PERFORMANCE CHARACTERISTICS OF LETOURNEAU SUPER C TOURNAPUUS ON HIGH­

WAY GRADING PROJECTS IN EASTERN AND SOUTHERN STATES

Equipment production studies made during the past two years on LeToumeau Super C Toumapull scraper units woricing on active r u r a l highvTay grading jobs i n eastern and southern States show that the average pay load was 9»6 cubic yards. The t o t a l time each unit spent i n loading, dumping, and turning,averaged 2,k minutes each rcund t r i p exclusive of delays. The haul and return speeds averaged 61*0 feet per minute.

These studies were conducted by the Production Cost Unit of the Bureau of Public Roads. The data presented i n t h i s report are a con^iosite summa­ry of observations made on random jobs and represent the perfoimance ob­tained by the contractors during the periods of study. No endeavor has been made to appraise the s i i i t a b i l i t y of the equipment for the p a r t i c u l a r jobs or to present selected data for purposes of enabling comparisons of perfonnance to be made with other types or c l a s s e s of equipment.

Nineteen units working on s i x differ e n t projects -irere observed for a period dtiring which 8,060 loads of material were moved. Pusher or p u l l e r t r a c t o r s were used during loading operations.

A v a r i e t y of c l a s s e s of material was encovintered on each job as w e l l as between jobs from "easy digging" i n comparatively l i g h t material to "hard digging" i n heavy c l a y . The average pay yardage ras computed on each job from load covints and the corresponding cubic yards of excavation obtained from cross sections.

Table 1 i s a composite summary of job average data r e l a t i n g to the Toumapull cycle elements and pay yardage per load. A l l delays have been excluded from the elements which are l i s t e d .

52

TABLE 1

SUI- MARY OF AVERAGE ROUND TRIP CYCLE DATA FOR 12.1 CUBIC YARD LETOURNEAU SUPER C TOURNAPULL SCRAPER UI«TS ON 6 RURAL HIGIWAY GRADING JOBS

IN EASTERN AM) SOUTHERN STATES

Element Range Average

1. Load 1.1--2.2 minutes l.k minutes 2. Dump and turn at f i l l O.k--0.7 minute 0.6 minute 3. Turn i n cut 0.2--0.5 minute O.k minute k. Total time constant (stun of

items 1, 2, and 3) 2.0-•3.2 minutes 2.k minutes 5. Haul distance k20. •1,890 feet 860 feet 6. Haul speed, loaded 14-70--1,110 feet/minute 620 feet/minute 7. Return speed, empty 370- •1,200 feet/minute 660 feet/minute 8. Pay haul distance 5itO--2,150 feet 9kO feet 9. Loading distance 120- • 260 feet 160 feet

10. Dumping distance 6o-•180 feet 110 feet 11. Pay yardage per load 8.2-•11.0 cubic yards 9.6 cubic yards

Haul distance, item 5, i s the distance traveled, excluding turning d i s ­tance, from the point the scraper gate i s closed a f t e r the load i s obtain­ed to the point where the scraper gate i s opened to discharge the load. Pay havl distance, item 8, i s the distance measured along the center l i n e of the roadway between the center of the inplace material loaded i n the cut to the center of t h i s same material dun^jed on the f i l l . The remaining items are l a r g e l y self-explanatory. I t i s i n t e r e s t i n g to note, however, that turning time i n the cut -sreis increased by 0.2 minute \Aien turns i n the cut were made a f t e r loading rather than before loading.

Ranges shown i n Table 1 are job averages. Daily variations, however, frequently exceeded the ranges which are shown. For example, the loading time on a p a r t i c u l a r job may have varied from O.k to 1.8 minutes, but only o v e r a l l job average was considered when l i s t i n g the entries i n Table 1

S u f f i c i e n t studies have not yet been made on t h i s p a r t i c u l a r type of \init to warrant appraisal of the individual e f f e c t upon performance char­a c t e r i s t i c s of such factors as condition of the unit, operator e f f i c i e n c y , t i r e i n f l a t i o n , condition of haul road, elevation, and e f f i c i e n c y of push­ing or pxaiing operations during loading.

COMMITTEE REPORT NO. 23 - MAY 1953 CLASSIFICATION OF MAINTENANCE AND REPAIR DELAYS OF 15 ^aN. OR MORE EXPERI­

ENCED BY RUBBER TIRED TRACTOR AND SCRAPER COMBINATIONS ON HIGHWAY GRADING JOBS

Maintenance and repair delays of 15 minutes or more each experienced by rubber t i r e d t r a c t o r and scraper combinations on active highway grading jobs account for a t o t a l down time to each unit of about I . 9 hours out of every 10-ho\ir work day. l / On some jobs down time due to such causes was more than double t h i s amount.

1/ Weather shutdowns are not considered part of the work day.

53

The magnitude of these losses \ras deteimined from studies conducted by the Bureau of Public Roads on 23 p r o j e c t s . Observations were made on 78 scraper units i n use during a combined woricing period of 7,200 hours. 2/ A t o t a l of 585 maintenance and repair delay occiirrences were experienced. On the average, one such time l o s s of 15 minutes or more takes place every 12.2 hours and i s about 137 minutes i n duration.

Table 1 shows ( l ) the p r i n c i p a l types of maintenance and repair delays encoxintered, (2) the percentage that each i s of the t o t a l meiintenance and repa i r delay time, and (3) the average duration of individ\ial delays.

Various c l a s s e s of excavation vrere encountered on these projects ranging from easy digging i n sandy s o i l s to hard digging i n material containing boulders and sizeable pieces of blasted granite. This l a t t e r type of material obviously contributes to the lik e l i h o o d of greater frequency of maintenance and repair delays to the t r a c t o r scraper u n i t . Haul distances ranged from l e s s than 100 feet to more than 5*500 feet over haul roads whose conditions varied from poorly maintained to we l l maintained.

TABIE 1

PERCENTAGE DISTRIBUTION AND AVERAGE DURATION OF 585 MAINTENANCE AND REPAIR DELAYS OF 15 MIN. AND OVER EXPERIENCED BY RUBBER TIRED TRACTOR AND SCRAPER COMBINATIONS ON HIGHWAY GRADING JOBS

Percentage of t o t a l Average dura­Type of delay maintenance and tion of each Type of delay

repair delay time delay repair delay time (Minutes)

1. Wait f o r repair parts 20 528 2. Tractor motor, transmission and

drive assembly ko 214.5 3. Tractor - other 12 100 h. Power control imit 11 136 5. Scraper control system - cable.

6 56 6.

hydraiilic l i n e s , e t c . 6 56 6. Scraper - other 6 66 7. Greasing, o i l i n g , and refueling _5 26

Total 100 137

An analysis was also made of the relationship between ( l ) shutdowns due to weather and (2) down time due to maintenance and repair. I t was foiind that both were at a maximxnn on those jobs vcpon which studies were made diiring the winter months.

There are other important factors which a f f e c t maintenance and repair delays, some of which are d i f f i c u l t to evaluate s p e c i f i c a l l y on a unifoim b a s i s . These include carefulness and e f f i c i e n c y of the operator, condi­tion of the equipment, sched\iled and nonscheduled repair and maintenance pra c t i c e s , and so on.

2/ Individual studies cover a calendar period of about three weeks during the active construction season. This f i e l d study program has been i n e f f e c t since 19^7.

COMMITTEE REPORT NO. 25 - JULY 1953 LENGTH OF HAUL FOR RUBBER-TIRED TRACTOR-AHD-SCRAPER COMBINATIONS

ON HIGHWAY GRADING JOBS

Studies of rubber-tired tractor-and-scraper combinations on highway-grading Jobs reveal that the observed t r a v e l distance, or apparent haul, from end of loading to s t a r t of dumping averages 925 feet. These studies were made over the past f i v e years by the Production Cost Unit of the Bureau of Public Roads on 19 grading jobs selected at random. Over 9,000 observations were made on 65 rubber-tired combinations ranging i n si z e from 5.91*0 ll^-.O cu. yd. struck capacity.

Figure 1 shows the percentage d i s t r i b u t i o n of t o t a l loads i n various increments of apparent haul. The number at the top of each bar i s the percentage value. The longest apparent haul observed was for four loads at 5,800 feet.

Apparent haul distances were arrayed according to scraper s i z e s to determine the relationship, i f any, between these two fa<:tors. For the p a r t i c u l a r jobs studied, no s i g n i f i c a n t relationship was found within the range of scraper s i z e s from 5'9 to ik.O cu. yd. struck capacity.

On the jobs studied, the true haul, or distance along a di r e c t path from midpoint of loading to midpoint of dumping, averaged 970 feet. I n computing true haul, adjustment was made for the fa c t that some loads were hauled over ci r c u i t o u s routes.

20-

IH

Percent of total observed loads

10

5J

200-ft. increments

6

I

Ik

'A

17 0

'A

18

1

14

\1 V/

l»O0-ft. Increments

lU V?

'A

5

I 'A v.

0 200 1*00 600 800 1000 ikOO 1800 2200 2600 to to to to to to to to to and 199 399 599 799 999 1399 1799 2199 2599 over

Length of apparent haul i n feet

Figure 1. Percentage d i s t r i b i i t i o n of t o t a l observed loads of rubber t i r e d t r a c t o r and scraper combinations by various apparent haul distances.

55

COMMITTEE REPORT NO. 15 - NOVEJffiER I9U9 OPERATING CYCIE OF PUSHER AND PULLER CRAWLER TRACTOIS WORKING IN

CONJUNCTION WITH RUBBER TIRED TRACTOR-DRAWN SCRAPER UI TETS ON HIGHWAY GRADING JOBS INIRSTERN AND SOUTHERN STATES

Equipment production studies made during the past year on pusher and p u l l e r crawler t r a c t o r s working i n conjunction with rubber t i r e d tractor-drawn scraper units on active r u r a l highway grading jobs show that each pusher or p u l l e r gives assistance i n the loading operation on the average of 2k times per hour. These studies were conducted by the Production Cost Unit of the Bureau of Public Roads, and the data presented i n t h i s report represent a composite summary of the observations made under a va r i e t y of job conditions and management p r a c t i c e s . No endeavor has been made to present selected data for purposes of enabling comparisons of per­formance to be made between various operating procedures or with other types or clas s e s of equipment under i d e n t i c a l operating conditions.

The studies cover operations of nine large pvisher and p i i l l e r crawler tr a c t o r s , from 80 to 1 *0 drawbar horsepower, on seven jobs i n eastern and southern States woricing i n conjunction with rubber t i r e d tractor-dram scraper u n i t s . The scrapers ranged i n s i z e from 8 to I3 cubic yards struck capsicity drawn by 2- and U-wheel rubber t i r e d t r a c tors having 110 to 135 drawbar horsepower. On the projects studied esich pusher or p u l l e r t r a c t o r worked with two to four scraper u n i t s .

Table 1 i s a composite summary for a l l jobs of the data r e l a t i n g to the pusher or p i i l l e r cycle elements, including waits and delays.

TABLE 1

CYCLE ELEME11TS OF PUSHER AND PULLER CRAWIER TRACTORS WORKING IN CONJUNCTION raTH RUBBER TIRED TRACTOR-DRAW SCRAPER UNITS

Item rr,. -, ^ Time i n minutes NO. Time element per cycle A^liH^

pushing or pul I'ing 0.9-l.k 1.1 2 Maneuvering: Backing, turning, and

engaging 0.5-1.2 0.8 3 Waiting for next scraper unit 0.0-1.0 O.k h Mnor delays 0.0-0.8 0.2 5 Total cycle 1.5-3.2 2.5

The pusher or p u l l e r cycle time i s considered to be the i n t e r v a l of time from the point where a given scraper unit i s engaged and aided i n loading by the pusher or p u l l e r t r a c t o r to the point where the next scraper unit i s s i m i l a r l y engaged. Time spent i n pushing or pu l l i n g during the loading operation, backing, turning, engaging, and miscellaneous waits and delays are considered as cycle elements.

Data irere obtained by timing several hiondred c y c l e s . The character of excavation varied on ea.ch job as well as between jobs from "easy digging" in loose, l i g h t , bulky materials to "hard digging" i n compacted clay or rocky materials. The ranges shoim i n Table 1 are job averages. On several of the projects the variations exceeded the ranges which are shovm. For example, the maneuver time may have varied from 0.2 to 2.3

56

minutes, but only the o v e r a l l job average was considered when l i s t i n g the entries i n Table 1.

Total cycle times shorn for item 5 i n Table 1 indicate that each pusher or p u l l e r gives assistance i n the loading operation from 19 to kO times per hour or an average of 2k times per hour for a l l jobs combined.

A m u l t i p l i c i t y of operating procedures was observed which precludes any detailed discussion of the individual cycle elements. I t i s i n t e r e s t ­ing to note, however, that there i s very l i t t l e difference between pusher operation and p u l l e r operation f o r the time spent i n loading and maneu­vering. A comparison i s shown i n Table 2.

TABLE 2

COMPARISON OF LOADING AND MANEUVERING TIME FOR PUSHER AND PULIER CRAWLER TRACTORS

Item Time i n minutes No- Time element per cycle Pusher P u l l e r

operation operation 1 A s s i s t i n loading scraper unit 1.12 O.98 2 Maneuvering: Backing, turning,

and engaging 0.79 O.89

3 Total, items 1 and 2 I.9I I .87

S u f f i c i e n t studies have not yet been made to warrant analyses of the individual e f f e c t upon scraper cycle elements and pay yardage per load of such factors as type of operation (pushing or p u l l i n g ) , s i z e and type of pusher or p u l l e r , kind of materials, grades, ground conditions, operator e f f i c i e n c y , and so on. Future reports on these matters w i l l be issued at such time as a s u f f i c i e n t number of studies are made to afford more positive indication of the e f f e c t of these f a c t o r s .

57

Other Equipment

COMMITTEE REPORT NO. li^ - NOVEMBER 19^9 PERFORMMJCE CHARACTERISTICS, PRODUCTION RATES, AND UTILIZATION OF AVAIIABIE WORKING TIME OF EUCLID BV LOADERS ON HIQIWAY GRADING

PROJECTS IN EAST CENTRAL STATES

Studies conducted during the past two years on three active r u r a l highvay grading projects reveal that Euclid BV Loaders excavated material at an average rate of 1,035 cubic yards per hour, exclusive of delays, exchanging time of hauling \mits, and turning time of the loader. When an allowance i s made f o r observed exchanging and turning time, the rate i s reduced to 705 cubic yards per hour. This rate i s s t i l l further affected by the delays which are experienced on various jobs.

These studies were conducted by the Production Cost Unit of the Bureau of Public Roads. The data presented i n t h i s report represent a composite sianmary of a var i e t y of job conditions and management practices. No en­deavor has been made to present selected data f o r the purpose of enabling comparisons of performance to be made with other types or classes of equipment.

The studies cover operations of three loaders during 213 hours of t o t a l available working time on three jobs i n east central States. The loaders worked with Euclid bottom dump wagons of 13 cubic yard struck capacity, and 3,6^1 loads were required to haul the 68,500 cubic yards excavated. The loaders were pvilled by large crawler t r a c t o r s . A pusher was occasionally used.

Table 1 shows the d i s t r i b u t i o n of the combined t o t a l available w r k i n g time f o r the three loaders.

TABLE 1

DISTRIBUTION OF 213 HOURS OF TOTAL AVAILABLE WORKING TIME FOR THREE EUCLID BV LOADERS ON THREE ACTIVE RURAL HIGHWAY GRADING PROJECTS

_. , . Percentage of t o t a l Time element available working time

Total available working time 100 Major delays 39 Net available working time 6l Minor delays 15 Productive time 16 Turning and exchanging time 15 Actual loading time 31

I n Table 1, the t o t a l available working time i s the sum of normal d a i l y s h i f t time plus such occasional overtime as actually •ivorked; major delays are i n d i v i d u a l delays of 15 minutes or more i n duration; and minor delays are indiv i d u a l delays of less than 15 minutes i n duration.

58 The extent of major delays of 15 minutes or more i n diiration due to

various causes i s shown i n Table 2. TABLE 2

CLASSIFICATION OF P4AJ0E DEIAY5 TO EUCLID BV LOADERS

Mature of major delay Percentage of t o t a l ^ available working time

Rain 12 Wet grade 5 Maintenance and repair of i m i t 19 Other 3

Total 39

The c l a s s i f i c a t i o n of minor delays i s shown i n Table 3. Individual delays are o r d i n a r i l y only a few seconds each i n duration and constitute 15 percent of the t o t a l available working time shown i n Table 1. However, t h e i r f u l l extent can usually be better visualized by comparing them t o the net available working time. For example, when minor delays are ex­pressed as a percentage of the t o t a l available working time, a job having frequent and extensive major delays, such as b£id weather, tends to show a lesser percentage of minor delays than a job having a few major delays. Thus, a better basis f o r indicating the extent of minor delays i n r e l a t i o n to the production operation i s t o express them as a percentage of the net available working time.

Minor delays amount t o one-fourth of the net available working time f o r the three jobs combined and varied on the individ u a l projects from 10 to 29 percent.

TABLE 3

CIASSIFICATION OF MINOR DELAYS TO EUCLID BV LOADERS

Nature of minor delay Percentage of net available wDiking time

Shortage of hauling units at the loader 17

Other hatiling u n i t delays 1 Maintenance and repair of uni t 2 Deadheeiding 1 Special handling of rock 1 Starting up or closing down 1 Other 2

Total 25 Materials encountered ranged from "easy digging" i n l i g h t bulky sandy

s o i l t o "hard digging" i n broken shale. A s c a r i f i e r was occasionally used to loosen materials i n order to f a c i l i t a t e the operation of the loader.

Perfomance characteristics and production rates of the loaders are shown i n Table k.

59 "EABIE k

AVERAGE PERFORMANCE CHARACTERISTICS AMD PRODUCTION RATES OF EUCLID BV LOADERS ON THREE ACTIVE RURAL HIGHWAY GRADING PROJECTS

Item Average l /

Loading time per load O.7I minute Exchange time of hauling units per load O.16 minute Turning time at end of furrow I . 0 6 minutes Loading distance per load 99 feet Cross section of b i t e 3*3 square feet Forward speed during loading 139 feet per minute Pay load carried by Euclid bottom duBip vagons having I3 cubic yard struck capsicity 12.1 cubic yards

Production per hour diiring t o t a l a v a i l ­able worfcing time 321 cubic yards

Production per ho\ir during net a v a i l ­able -working time 52? cubic yards

Production per hour diiring productive time 705 cubic yards

Production per hour of loading time 1^035 cubic yards

1/ Any s l i g h t discrepancies which may be involved i n the above figures are due to using round numbers.

The foregoing cycle data were procured by timing more than a thousand in d i v i d t i a l loads. The yardage data were obtained from load counts, and the corresponding cubic yards of excavation obtained from cross sections on each job.

S u f f i c i e n t studies have not yet been made on t h i s p a r t i c u l a r type of equipment to warrant conclusive analysis of the ef f e c t upon production of such factors as operating efficiency, kind of material, and so on. Length of furrow, grades, and p r o f i l e are likewise elements that are of major significance i n evalxiating the performance of t h i s type of equipment.

COMMITTEE REPORT NO. 20 - NOVEMBER 1950 PERFORMANCE CHARACTERISTICS, PRODUCTION RATES, AND UTILIZATION OF TOTAL AVAILABLE WORKING TIME OF THE P&H SINGLE PASS SOIL STABILIZER ON HIGHWAY

STABILIZATION PROJECTS IN EASTERN AND CENTRAL STATES

Production studies made during the past three years on f i v e active r u r a l highway s t a b i l i z a t i o n projects reveal that the Single Pass S o i l S t a b i l i z e r processed single ti-foot sections of readway at an average rate of 1,^72 feet per hoiir, exclusive of a l l delays, maneuvers, and turns. When an allowance i s made f o r the time required f o r necessary maneuvere and turns at the end of each single pass section, the rate i s reduced t o 1,3^ feet per hour. This rate i s s t i l l f urther reduced by the delays which are experienced on various jobs. The s t a b i l i z i n g process performed by t h i s machine embraces f i v e operations conducted simultaneously during a single pass. Uiese are described by the manufacturer as ( l ) shaving and pulverizing the inplace material, (2^ blending a l l dry materials, (3) applying l i q u i d s , (4) mixing, and (5) spreading.

6o These studies were conducted by the Production Cost Unit of the Bureau

of Public Roads. The data presented i n t h i s report are a composite sum­mary of observations made and represent the perfomance obtained by the contractor during the periods of study. No endeavor has been made ( l ) to appraise the s u i t a b i l i t y of the equipment f o r the p a r t i c u l a r jobs; (2) t o present selected data f o r the purpose of enabling comparison of per-fonnance to be made v i t h other types or classes of equipment; or (3) t o evaluate the e f f e c t upon perfoimance of such factors as condition of the equipment, operator e f f i c i e n c y , character of material, grades, depth of section, and so on.

The studies cover operations of f i v e s t a b i l i z e r s diiring 720 hours of t o t a l available vorking time on f i v e Jobs i n eastern and central States. During t h i s period the s t a b i l i z e r s processed 68.6 miles of 8-foot wide sections using bituminous s t a b i l i z i n g admixtures on t-vro jobs and portland cement on three jobs. The bituminous s t a b i l i z e d sections were constructed to a compacted depth of f i v e and seven inches, and the portland cement st a b i l i z e d sections to a depth of s i x inches. Hie widths being s t a b i l i z e d ranged from 16 t o 2k feet on the d i f f e r e n t jobs. T\^o t r i p s were required to complete the l6-foot widths •vrtiile three t r i p s were necessary f o r proc­essing the greater widths.

Materials encountered ranged from "easy digging" i n sandy so i l s or newly graded roadbeds to "hard digging" i n ex i s t i n g compacted surfaces containing large amounts of coarse granular material. Where hard digging was encountered, i t was the usual practice t o scsurify p r i n c i p a l l y f o r the purpose of removing the larger boulders or rocks i n advance of the passage of the s t a b i l i z e r . Average processing speeds observed on the variovus jobs ranged from 1,103 t o 1,682 feet per hour, exclusive of a l l delays, maneu­vers, and t\mis.

Table 1 shows the d i s t r i b u t i o n of the combined t o t a l available working time f o r the f i v e s t a b i l i z e r s .

TABLE 1

DISTRIBUTION OF 720 HOURS OF TOTAL AVAIIABLE WORKING TIME FOR 5 P&H SINGIE PASS SOIL STABILIZERS ON 5 ACTIVE RURAL HIGHWAY

STABILIZATION PROJECTS

Timf' element Percentage of t o t a l available working time

(Average) Total available working time 100 Major delays 56 Net available woriting time kh Minor delays 6 Productive time 38 Maneuvers and turns at end of each section 3

Actual processing time 35

I n Table 1, the t o t a l available working time i s the stmi of noimsLL d a i l y s h i f t time plus such occasional overtime as actually worked; major delays axe individxial delays of 15 minutes or more i n duration; and minor delays are i n d i v i d u a l delays of less than 15 minutes i n duration.

6i Ihe extent of major delays of 15 minutes or more i n duration due to

various causes i s shown i n Table 2,

TABLE 2

CLASSIFICATION OF MAJOR DELAYS TO P&H SINGLE PASS SOIL STABILIZER

Nature of major delay Percentage of t o t a l available working time

Rain and wet grade 17 Lack of s t a b i l i z i n g admixture at 17 job s i t e 15 Lack of water at job s i t e 2

Maintenance and repair of u n i t 11 Wait on subgrade preparation 6 Starting delays 1 Other k

Total 56 The c l a s s i f i c a t i o n o f minor delays i s shown i n Table 3. Individual

minor delays are ordinajrily only a few seconds esich i n duration and con­s t i t u t e s ix percent of the t o t a l available working time shown i n Table 1. However, t h e i r f u l l extent can usually be better visualized by comparing them to the net available working time. For example, -vrtien minor delays are expressed as a percentage of the t o t a l available woiicing time, a job having frequent and extensive major delays, such as bad i/eather, tends to show a lesser pereenteige of minor delays than a job having a few major delays. Thus, a better basis f o r indicating the extent of minor delays i n relation to the production operations i s t o express them as a percentage of the net available working time.

Minor delays amount to ih percent of the net available woiicing time f o r the f i v e Jobs combined and varied on the i n d i v i d u a l projects from 5 t o 22 percent.

TABLE 3

CIASSIFICATION OF MINOR DEIAYS TO THE P&H SINGIE PASS SOIL STABILIZER

T v T = + „ . ^ - . - . ^ ^ v . ^=io,r Percentace of net available Nature of minor delay working time

Lack of s t a b i l i z i n g admixture at job s i t e 3 Lack of water at job s i t e k

Maintenance and repair of u n i t 2 Instructions, engineering, etc. 1 Clean and replace digging teeth 1 Other 3

Total Ik

Maneuvers and turns at the end of single pass sections were observed to require an additional seven percent of the net available working time.

62 COMMITTEE REPORT NO. 32 - JUNE 1957

UTIUZATION OF AVAIIABLE WORKING TIME OF ROCK CRUSHING PIANTS ON HIGHWAY CONSTRUCTION PROJECTS

Equipment production studies made on rock cjrushing plants show that 39 percent of the t o t a l available working time i s l o s t i n delays. Hiese studies were made by the Production Cost Section of the Bureau of Public Roads, and include data on 11 portable and stationary crushers, producing base and surfacing materisils exclusively f o r high^ray projects.

Ifeterials encountered ranged from gravels to quarried basalt. Crushers included one single-ianit haramermill, with the remaining setups consisting of multiple combinations of jaw, cone, and r o l l crushers.

Table 1 shows the d i s t r i b u t i o n of 3 035 hours of t o t a l available work­ing time as determined from these studies. No time f o r move i n , set up, move out, or standby has been included. I n the table, the t o t a l available •\rorking time i s the sum of normal s h i f t time plus any overtime actually TOiked, major delays are individual time losses of 15-minute or longer diiration, and minor delays are i n d i v i d u a l time losses of less than 15-minute duration.

TABLE 1

DISTRIBUTION OF 3,035 HOURS OF TOTAL AVAILABLE WORKING TIME FOR ROCK CRUSHING PLANTS PRODUCING BASE AND SURFACING MATERIALS

EXCLUSIVELY FOR HIGHWAY PROJECTS

Time element

Total available working time Major delays Net available working time Minor delays Actual productive time

Percent of t o t a l available working time

Range 100

k-k6 3k-96 k-kl 35-87

Average 100 21 79 18 61

Hie extent and cause of major delays i s indicated i n Table 2.

TABLE 2

CLASSIFICATION OF MAJOR DELAYS TO ROCK CRUSHING PIANTS

„ . „ . , , Percent of t o t a l available Nature of major delay working time

Itepairs t o plant tointenance and adjustment of plant Vleather delays, including \ret grade Shortage of material at feeder Oversize material or overloading A l l other

Total

9 2 3 3 1

_3 21

63 Almost one-half of the repair delay time was attributable to the crush­

ing xmits, with the rest about equally divided among screens, conveyors, power units, and drive systems.

I n the category of shortage of material, two-thirds of the delay time was accoimted for i n repair and maintenance of the loading unit, with s t r i p ­ping, or d r i l l i n g and bla s t i n g accounting for most of the rest.

Table 3 shows the c l a s s i f i c a t i o n and extent of minor delays. Although minor delays are of short duration (on these jobs the aversige duration of each minor delay was 1.7 minutes), i t w i l l be noted i n Table 1 that they amount to l8 percent of the t o t a l available working time. However, the f u l l extent of minor delays can be better v i s u a l i z e d by comparing them with the net available working time. When minor delays are expressed as a pereentEige of t o t a l available -vrorking time, a job with frequent and extensive major delays might show a proportionately smaller percentage of minor delays than a job with fewer major delays. Thus a better basis for indicating minor delays i s to express them as a percentage of the net a v a i l ­able working time.

TABLE 3

CIASSIFICATION OF MINOR DELAYS TO ROCK CRUSHING PLAINTS

Type of delay Percent of net available working time

Wait for haiJling units at crusher delivery b e l t or bunker l / 10

Oversize material or overloading 5 Shortage of material at feeder h Maintenance and adjustment of crusher 1 St a r t l a t e , excess lunch, quit e a r l y 1 A l l other 2

Ttotal 23 1/ Includes hauling u n i t exchange

I t can be seen from Table 3 that waits for hauling units accounted for 10 percent of the net available working time (NAWT) and more than kO per­cent of a l l minor delay time. This i s a s i g n i f i c a n t amount and i s affected by the presence or absence of a loading bunker. For exaniple, on jobs where trucks were loaded d i r e c t l y frem the delivery b e l t t h i s delay averaged l6 percent of the NAWT; however, when loading was frcm a blanker the delay was only three percent. U i i s suggests that minor delays frcm t h i s cause can be materially reduced by use of a bunker. However, a reduction i n one type of delay i s often accompanied by increases i n other types, as indicated by Table k. I t should be noted that other delays increased frcm 11 to 15 per­cent when wait-for-hauling--unit delays were reduced frcm l6 to 3 percent. The net advantage of the bunker as indicated by these studies i s nine percent of the NAWT.

6h

TABLE k

MINOR DEIAYS TO ROCK CRUSHING PLAIvITS

Percent of net available working time

Type of delay

Wait f o r hauling units Other

Total

Crushers which loaded trucks from bunker

3 15 18

Crushers which loaded trucks d i r e c t l y from delivery b e l t

16 11 27

A l l Crushers

10 13 23

COMMITTEE REPORT NO. 1 - MARCH 19h9 UTILIZATION OF AVAILABLE WORKING TIME OF MAJOR EQUIPMENT ON ACTIVE HIGHWAY

CONSTRUCTION JOBS IN EASTERN STATES

Equipment production studies being conducted by the Production Cost Unit of the Public Roads Administration on active highway construction jobs reveal that from t o 80 percent of the t o t a l available working time of major equipment i s being l o s t i n delays. This fact i s obtained from an analysis of the f i e l d studies made during 19^7 and I9U8 on 33 t y p i c a l grading and surfacing jobs i n eastern States.

The summaries embrace a t o t a l of 55 major units of equipment including dual drum pavers, asphalt plants, bituminous fin i s h e r s , scrapers, shovels, and s t a b i l i z i n g machines f o r a combined period of 5 39 hours t o t a l a v a i l ­able working time.

I n Table 1 i s shown the percentage d i s t r i b u t i o n of t o t a l available woiic-ing time f o r a l l kinds and sizes of equipment, combined. The figures are sig n i f i c a n t only to the extent that they show the approximate degree to \diich major construction equipment i s actually u t i l i z e d during the periods that -work, i s underway on active highway construction projects.

TABLE 1 DISTRIBUTION OF TOTAL AVAIIABLE WORKING TIME FOR MAJOR UNITS OF EQUIPMENT

ON ACTIVE HIGHWAY CONSTRUCTION PROJECTS

Time element

Total available working time Major delays l / Net available working time Minor delays 2/ Actiial productive working time

Percent of t o t a l available woricing time

Range 100 33-63 37-67 4-28 20-55

Average 100 15 11 39

1/ Individual delays of 15 minutes or more i n duration. 2/ Individual delays of less than 15 minutes i n duration.

65

The t o t a l available working time i s the sum of ( l ) normal 1 y scheduled d a i l y s h i f t time and (2) 'such occasional overtime as actually worked. Ihus, i f a job had a scheduled s h i f t time of eight hours d a i l y f o r f i v e days a week, and two hours overtime vras worked on one of those days, the t o t a l available working time f o r that day would be 10 hours. I f Saturday WEIS not a scheduled work day, but eight hours were worked on Saturday to make up f o r time l o s t because of bad weather, these eight hours would be i n ­cluded as part of the t o t a l available working time.

A major delay i s an individual time loss of 15 minutes or more i n dura­t i o n which occurs within the t o t a l available working time. Major delays do not normally occur with any p a r t i c u l a r regularity. Nearly h a l f of a l l major delays are due to weather conditions. Other major delays are caused p r i n c i p a l l y by waiting upon a u x i l i a r y equipment, equipment breakdowns, and shortages of materials.

A minor delay i s an individual time loss of less than 15 minutes i n du­ra t i o n . Although minor delays usually occur f o r j u s t a few seconds, they frequently add up to si g n i f i c a n t amoiuits i n t o t a l . They are also due to a large v a r i e t y of reasons, the p r i n c i p a l ones being shortages of materisils on surfacing jobs, shortages of hauling units on a l l jobs requiring haul­ing \mits, and equipment repairs.

The majority of major delays are not as costly as minor delays. Many major delays, such as weather, cause the job to shut down over an extended period, thus reducing the contractor's pay rcll and other current expense during the delay. During such major delays, however, charges f o r overhead, demurrage, etc., are incurred. During minor delays, on the other hand, the current expense i s at a maximum since the contractor i s working with a f u l l coniplement of men and equipment.

Detailed svmmiaries of the kind and extent of time losses experienced by specific classes of equipment w i l l be reported by the Committee i n the near future.

66

HIGHWAY MAINTENANCE OPERATIONS

COMMITTEE REPORT NO. 28 - JANUARY 1955 DISTRIBUTION OF LABOR TIME ON HAND PATCHING OF BITUIvIINOUS ROAD SURFACE

Studies of hand patching of bituminous road sxxrfaces by State highway maintenance crews show that, on the average, 28 percent of the crew time i s used f o r perfonning actual work on the patch. Hie remaining 72 per­cent i s accounted f o r i n preparatory and incidental operations, waits, and delays. Over 1,000 man-hours of crew time were studied, covering both hot and cold mix patches and spot sealing. Studies Involving use of motor graders i n patching operations are not included.

TABLE 1

DISTRIBUTION OF LABOR HOURS OF AVAILABLE WORKING TDffi ON HAND PATCHING OF BITUMINOUS ROAD SURFACES

Group Percent of crew time A-verage Ranges

Actual work on the patch Prepare pavement Tacking Spread and smooth mix Roll patch Group t o t a l

3 3 20 2 28

Preparatory and incidental operations Travel between garage and work s i t e 12 Itove to next patch or worksite 9 T r a f f i c control 5 Load and unload truck at yard or worksite 6

Obtain-' additional material 7 Miscellaneous 6

Group t o t a l k3 32-62 Walts and delays Walts during crew ^rork 17 Instructions and supervision 1 Start l a t e , excess lunch, quit early 2

I d l e , personal delays and resting 3 Other h

Group t o t a l 27 Grand t o t a l 100

13-hh

67

Table 1 shows i n summary form the average d i s t r i b u t i o n of labor time i n t o three p r i n c i p a l groupings with subitems f o r each group. The ranges (low and high) f o r each group are also shovm. These ranges are arithme­t i c averages of the f i v e lowest and f i v e highest values observed among 2k studies made by the Bureau of Public Roads i n ll; States.

Operations included under Group 2 i n Table 1 are generally essential to the perfonnance of a day's work. They do not, however, represent actual work i n placing the patch. Some of the waits and delays included i n Group 3 are, without doubt, unavoidable.

I t i s of interest to note that i f i t were possible to reduce the sum of Groups 2 and 3 by, say seven percentage points from 72 percent to 65 percent, the apparent eff e c t would be t o increase d a i l y accomplishment (Grov^) 1) by a fourth.

With the exception of those studies where motorgraders were used (these studies are not included i n t h i s report) no s i g n i f i c a n t differences were observed with respect to time d i s t r i b u t i o n among the various groups, whether hot or cold mix patching or spot sealing. Daily accomplishment varied widely between the various types of patching operations. I t also varied widely w i t h i n each operation, even on successive days by the same crew. Following i s a l i s t i n g of t y p i c a l accomplishments observed f o r a four-man crew during an 8-hour worfc ,day. The 8-hour work day i s approxi­mately the average of the Ik States i n which studies were made.

Type of patching operation Typical d a i l y accomplishment of a four-man crew i n an o-hour work day

Placing cold mix patch, old pave­ment removed by hand 22 patches t o t a l i n g k6 sq. yd., or

Placing cold mix patch, tacked, no old pavement removed

Not r o l l e d 2lk patches t o t a l i n g 400 sq. yd., or Rolled 137 patches t o t a l i n g 255 sq. yd., or

Spot sealing 80 patches t o t a l i n g 1,025 sq. yd.

COMMITTEE REPORT NO. 17 - MAY 1950 UTILIZATION OF AVAILABLE WORKING TIME OF MOTORGRADERS ON COUNTY ROAD

VTORK IN SOUTEffiRN STATES

Equipment production studies made during the lat e summer and f a l l of 19k9 on motorgraders on county road work revesil that t h i s class of equip­ment i s u t i l i z e d on actual productive work f o r kj percent of the t o t a l available working time. These studies were conducted by the Production Cost Unit of the Bureau of Public Roads on k3 motorgraders operated i n f i v e counties i n three southern States. The majority of the motorgraders carried 12-foot blades, were less thaji 10 years old, and were i n good mechanical condition. A l l of the motorgraders were owned by the counties and were operated by county personnel. On the average about 60 percent of the t o t a l available woiking time was spent on routine maintenance and ditching work, whereas the remaining kO percent was on a v a r i e t y of other operations such as gravel spreading, o i l mixing, and heavy grading.

Table 1 shows the percentage d i s t r i b u t i o n of 1,526 hours of t o t a l available working time as obtained from the studies. These and other data

68 contained i n t h i s report reflect only the conditions that prevailed during the period from August t o October 19^9, and should not be interpreted as representative of year-round iisage.

TABLE 1

DISTRIBUTION OF TOTAL AVAILABIE WORKING TIME OF MOTORGRADERS ON COUNTY ROAD WORK

Time element

Total available vrorking time Major delays Net available working time Minor delays Actual productive time

Percent of t o t a l available working time

Range 100 19-57 U3-81 9-21 3i -57

Average 100

• ko 60 13 hi

I n Table 1, the t o t a l available working time i s the sum of normal d a i l y s h i f t time plus such occasional overtime as actually wrked; major delays are individ u a l delays of 15 minutes or more i n duration; and minor delays are individ u a l delays of less than 15 minutes i n diiration. The ranges sho-im i n Table 1 are composite averages f o r a l l motorgraders i n a county during the period of study.

Olie extent of major delays of 15 minutes or more i n duration due to various causes i s shown i n Table 2.

TABLE 2

CLASSIFICATION OP MAJOR DELAYS TO MOTORGRADERS ON COUNTY ROAD V70RK

Nature of major delay Percentage of t o t a l available irorking time

Bad weather Operator i n - t r a n s i t time to job s i t e , excess lunch hour, q u i t t i n g early-

Standby i d l e Repair and maintenance of vanit Deeidheading Other

Total

11 8 7 6 2 6

ho

The practice with respect t o having the county crews report f o r work iras varied. I n some instances the men reported f o r work at the job s i t e •vdiile i n others they reported f o r \rork at the county shop and then were transported to the job s i t e . These l a t t e r instances accounted f o r a portion of the major delays included i n the second item i n Table 2. I n a l l cases, hov/ever, the s h i f t time ended on the job and did not include i n - t r a n s i t time back to the county shop.

The c l a s s i f i c a t i o n of minor delays i s shown i n Table 3. Minor delays are o r d i n a r i l y only a few seconds each i n duration, and i n Table 1 i t ^•^±ll be noted they amount t o 13 percent of the t o t a l available worfting time. Ho\rever, the f u l l extent of minor delays can usually be better

69 visualized by coniparing them to the net available working time. For ex-an?>le, -vdien minor delays are expressed as a percentage of the t o t a l avsill-able working time, an area having frequent and extensive major delays such as bad weather tends t o show a lesser percentage of minor dele^rs than an area having a few major delays. Thus, a better basis f o r indicating the extent of minor delays i n r e l a t i o n t o the production operation I s to ex­press them as a percentage of the net available worfcing time.

I n the f i v e counties i n which studies were conducted, minor delays varied from l6 t o 30 percent of the net available worfcing time with an average of 22 percent.

TABIE 3

CIASSIFICATION OF MINOR DEIAYS TO MOTORGRADERS ON COUNTY ROAD WORK

Maneuvers and turns 5 Deadheading k Waiting on other graders or equip­ment k

Personnel k Repair and maintenance of u n i t 1 -Other k

Total 22 Most of the routine maintenance blading was accomplished i n two t r i p s

by the motorgraders once over each h a l f of the roadway, and the ove r a l l average was found t o be 2.1 t r i p s on a l l road sections. Travel speeds of the motorgraders were observed t o range from 3.3 t o h.2 miles per hour by counties with an average of 3'9 miles per hour. Routine d i t c h p u l l i n g was performed at a somewhat slower rate, with t r a v e l speeds averaging 2.k miles per hour and ranging from 2.0 t o 2.7 miles per hour.

With the inclusion of minor delays i t was observed that the average motorgrader completed I.5 miles of bladed road per hour and that t h i s rate ranged from 0.9 to 1.8 miles per hour by counties.

COMMITEEE REPORT NO. I8 - JULY 1950 UnnZATION OF AVAIIABIE WORKING TIME OF TRACTOR FRONT-END LOADERS IN

BORROW PITS ON COUNTY ROAD WORK IN SOUTHERN STAT^

Equipment production studies made diiring the l a t e summer and f a l l of 19^9 on t r a c t o r front-end loaders on county road work reveal that lack of hauling xmits at the loEiding s i t e constitutes the greatest single source of delay t o t h i s class of equipment while engaged i n loading select mate­r i a l i n borrow p i t s . These studies were conducted by the Production Cost Unit of the Bureau of Public Roads on seven loaders operated i n three counties i n two southern States. One loader had a 7/8-cublc yard capacity, idiereeis the others were a l l of one-cubic yard capacity. I n each instance they were owned by the county and were operated by county personnel. Five of the loaders were manned with f u l l - t i m e operators, but i n two cases the hauling u n i t drivers loaded t h e i r own trucks.

70 Table 1 shows the percentage d i s t r i b u t i o n of 315 hours of t o t a l a v a i l ­

able working time as obtained frcm the studies. These and other data contained i n t h i s report reflect only the conditions that prevailed while working i n borrow p i t s from August t o October 19* 9* snd. sho\Ald not be interpreted as representative of year-rcund usage during which t h i s equipment may be employed on a va r i e t y of operations, such as cleaning up slides, loading slough bladed frem ditches, loading stocked materials, and so on.

TABIE 1

DISTRIBUTION OF TOTAL AVAIIABIE WORKING TIME OF TRACTOR FRONT-END LOADERS IN BORROW PITS ON COUNTY ROAD WORK

Time element

Total avEiilable working time Major delays Net available vrorking time Minor delays Actual preductive time

Percentage of t o t a l available TOrking time

Range 100 kh-d2 18-56 8- 19 9- 37

Average 100 68 32 16 16

I n Table 1, the t o t a l available working time i s the sum of normal d a i l y s h i f t time plus such occasional overtime as actually worked; major delays are individ u a l delays of 15 minutes or more i n duration; and minor delays are i n d i v i d i i a l delays of less than 15 minutes i n duration. The ranges shown i n Table 1 represent averages f o r each loader diiring the period of study.

The extent of major delays of 15 minutes or more i n duration due t o various caiises i s shown i n Table 2.

TABLE 2

CLASSIFICATION OF MAJOR DELAYS TO TRACTOR FRONT-END LOADERS IN BORROW PITS ON COUI TY ROAD WORK

Mature of major delay

Bad weather Repair and maintenance of u n i t Lack of hauling units at loading s i t e

Operator i n - t r a n s i t time t o job s i t e , excessive Ivmch hour, q u i t t i n g early-

Standby i d l e Other

TDtal

Percentage of t o t a l available ^forking time

21 17 15 7 3

2 68

The practice with respect t o having the county crews report f o r w r k •VTSS varied. I n some instances the men reported f o r \rork at the job s i t e , •vdille i n others they reported f o r -irork at the county shop and then were transported t o the job s i t e . These l a t t e r instances accounted f o r a

71 portion of the major delays included i n the fourth item i n Table 2. I n a l l cases, however, the s h i f t time ended on the job and did not include i n - t r a n s i t time back to the county shop.

The c l a s s i f i c a t i o n of minor delays i s shown i n Table 3. Minor delays are o r d i n a r i l y only a few seconds each i n duration, and i n Table 1 i t w i l l be noted they amount to l6 percent of the t o t a l available woiking time. However, the f u l l extent of minor delays can usually be better visualized by comparing them to the net available working time. For ex­ample, when minor delays are expressed as a percentage of the t o t a l a v a i l ­able working time, an area having frequent and extensive major delays such as bad weather tends to show a lesser percentage of minor delays than an area having a few major delays. Thus, a better basis f o r indicating the extent of minor delays i n relation t o the production operation i s t o express them as a percentage of the net available working time.

For the seven loaders on -vrtiich studies were conducted, minor delays varied from 3^ t o 65 percent of the net available working time with an average of h9 percent.

TABLE 3

CLASSIFICATION OF MINOR DELAYS TO TRACTOR FRONT-END LOADERS IN BORROW PITS ON COUNTY ROAD WORK

Nature of minor delay

Lack of hauling units at loading s i t e Personnel Hauling u n i t maneuvers and delays Repair and maintenance of u n i t Maneuvers by the loader t o maintain digging position or clean up work s i t e

Other Total

Percentage of net avedlable working time

35 3 2 2

1 _6 h9

Table 4 i s a composite summary f o r a l l loaders of the data relating t o the cycle elements of the u n i t .

TABLE k

SUMMARY OF THE AVERAGE CYCLE DATA FOR TRACTOR FRONT-END LOADERS IN BORROW PITS ON COUNTY ROAD WORK

1/ Excludes a l l delays.

Element Range Average 1. Load 8-I9 seconds 13 seconds 2. Maneuver to dump s i t e 10-23 seconds 15 seconds 3. Dump 1- h seconds 2 seconds k. Return 8-I9 seconds Ik seconds 5. Total cycle (sum of items 1, 2,

3, and k) l / 31-65 seconds kh seconds

During the study of each loader an estimate was made of the pay yards loaded i n each truck, and the resulting t o t a l was converted t o average

72 cubic yards per bucket of the loading u n i t . The composite yardage sum­mary f o r a l l loaders indicates an average pay load of 80 percent of the rated capacity with a range between loaders of 71 t o 87 percent.

A con?)utation based on the productive woiking time rate of the units and the estimated yardage per bucket load shows that the composite average production rate of the xmits was 65 cubic yards per hour with a range between loaders of 58 t o 87 pay cubic yards per hour of actual productive time, exclusive of a l l delays.

S u f f i c i e n t studies have not yet been made to warrant analyses of the indivi d u a l e f f e c t upon cycle elements and pay yardage of such factors as condition and type of u n i t , kind of material, height of digging face, operator eff i c i e n c y , and so on.

COMMITTEE REPORT NO. 19 - SEPTEMBER 1950 UTIUZATIOK OF AVAIIABLE WORKING TIME OF |-CUBIC YARD POWER SHOVEL AND

DRAGLINE UNITS ON COUNTY ROAD WORK IN SOUTHERN STATES

Equipment production studies made during the l a t e summer and f a l l of 19k9 on power shovel and dragline units on coimty road work reveal that t h i s class o f equipment i s u t i l i z e d on actual productive work f o r 37 per­cent of the toteJ. available working time. The studies -v/ere conducted by the Production Cost Unit of the Bureau of Public Roads on one power shovel and three draglines operated i n three counties i n three southern States. A l l four units were owned by the counties, were operated by county personnel, and were of |-cubic yard capacity. Three of the units loaded select material, whereas the fourth u n i t was on ditch excavation during the period of study.

Table 1 shows the percentage d i s t r i b u t i o n of 111 hours of t o t a l a v a i l ­able working time as obtained from the studies. These and other data contained i n t h i s report r e f l e c t only the conditions that prevailed during l i m i t e d periods of study from August to October 19* 9, and should not be interpreted as representative of year-round usage.

TABLE 1

DISTRIBUTION OF TOTAL AVAILABLE WORKING TIME OF 5-CUBIC YARD POV/ER SHOVEL AND DRAGLINE UNITS ON COUNTY ROAD VJORK

Time element

Total available working time Major delays Net available working time l^inor delays Actual productive time

Percentage of t o t a l available working time

100 27-1 3 57-73 20-32 30-52

Average 100

37 ^1 26 37

I n Table 1, the t o t a l available iraricing time i s the sum of normal d a i l y s h i f t time plus such occasional overtime as actually irorked; major delays are i n d i v i d u a l delays of I5 minutes or more i n duration; and minor delays are individ\jal delays of less than 15 minutes i n diiration. The ranges shown i n Table 1 represent averages f o r individual power shovel or drag­l i n e units during the period of study.

73

The extent of major delays of 15 lainutes or more i n duration due to various causes i s shown i n Table 2.

TABLE 2

CLASSIFICATION OF MAJOR DEIAYS TO POWER SHOVEL MID DRAGLINE UOTTS ON COUIOT ROAD WORK

Nature of major delay Percentage of t o t a l available working time

Bad TOather 0 Lack of hauling units at loading s i t e 20

Repair and maintenance t o shovel or dragline 7

Operator i n - t r a n s i t time to job s i t e , excess lunch hour, q u i t t i n g early 5

Other 5 Total 37

Weather conditions were favorable throughout the pajrticular study period. This class of delay i s l i s t e d i n Table 2, ho^rever, to c a l l atten­t i o n to the fact that a certain amount of delay from t h i s source \i±ll or­d i n a r i l y be experienced.

The practice with respect t o having the county creire report f o r work was varied. I n some instances the men reported f o r woik at the job s i t e , \Aiile i n others they reported f o r vork at the county shop and then were transported t o the job s i t e . These l a t t e r instances accounted f o r a por­t i o n of the major delays included i n the foxirth item i n Table 2. I n a l l cases, ho\rever, s h i f t time ended on the job and did not include i n - t r a n s i t time back to the county shop.

The c l a s s i f i c a t i o n of minor delays i s shoim i n Table 3. Minor delays are o r d i n a r i l y only a few seconds i n duration, and i n Table 1 i t vlH be noted they amount to 26 percent of the t o t a l available woricing time. How­ever, the f u l l extent of minor delays can usually be better visualized by comparing them to the net available working time. For example, when minor delays are expressed as a percentage of the t o t a l available \rorking time, an area having frequent and extensive major delays such as bad weath­er tends t o show a lesser percentage of minor delays than an area having a few major delays. Thus, a better basis of comparison f o r indicating the extent of minor delays i n r e l a t i o n to the production operation i s to express them as a percentage of the net available working time.

For the four power shovel and dragline units upon which studies were conducted, minor delays varied from 28 t o 52 percent of the net available working time with an average of kl percent.

TABLE 3

C I A S S I F I C A T I O n OF MINOR DEIAYS TO POVJER SHOVEL AND DRAGLINE UI\riTS ON COUI-ITY ROAD WORK

Nature of minor delay Percent of net available working time

Lack of hauling units at loading s i t e

Short moves to maintain digging position Trimming and cleaning up vroik s i t e Waiting -while hauling u n i t maneuvers in t o position t o obtain load

Repairs and maintenance to power shovel or dragline

Personnel Other

Total

27 5 k

1 1 2

hi

Table li- i s a composite summary of average data r e l a t i n g to the power shovel and dragline cycle elements. A l l delays have been eliminated from the elements which are l i s t e d .

TABLE k

SUMMARY OF AVERAGE CYCIE DATA FOR 5-CUBIC YARD POWER SHOVEL AND DRAGLINE UNITS ON COUNTY ROAD

Element

1. Load 2. Swing 3. Dimp h. RetTim 5. Tot8LL cycle time (sum of

items 1, 2, 3, and i^)

Range

5-13 seconds 3 -1 -k -

seconds seconds seconds

Average

10.2 seconds k.Q seconds 1.2 seconds 6.0 seconds

13 - 31 seconds 22.2 seconds

The minimum cycle time observed was f o r a -l^cubic yard power shovel operating i n a chert bank, whereas the maximum cycle was f o r 5-cubic yard dragline engaged i n ditch excavation.

The cycle data were obtained by timing several hundred indivi d u a l cycles. The ranges shown are averages f o r each of the u n i t s . A l l obser­vations were made \Aiile the units were loading trucks. Uie average pay yardage per dipper load was estimated to be about O.k cubic yard as ob­tained from dipper load counts and corresponding estimates of the pay yardage hauled by the trucks. The average angle of swing during the ob­servations was 53 degrees.

Suffici e n t studies have not yet been made to warrant anaJLyses of the in d i v i d u a l e f f e c t upon the performance of ^ c u b i c yard power shovels or draglines on county road work of such factors as condition and type of u n i t , kind of material, boom angle, dipper p i t c h , height of digging face, operator efficiency, type and size of hauling vinit, and so on.

r p H E NATIONAL ACADEMY OF SCIENCES—NATIONAL RESEARCH COUN-I CIL is a private, nonprofit organization of scientists, dedicated to the

furtherance of science and to its use for the general welfare. The ACADEMY itself was established in 1863 under a congressional charter signed by President Lincoln. Empowered to provide for all activities ap­propriate to academies of science, i t was also required by its charter to act as an adviser to the federal government in scientific matters. This provision accounts for the close ties that have always existed between the ACADEMY and the government, although the ACADEMY is not a govern­mental agency.

The NATIONAL RESEARCH COUNCIL was established by the ACADEMY in 1916, at the request of President Wilson, to enable scientists generally to associate their efforts with those of the limited membership of the ACADEMY in service to the nation, to society, and to science at home and abroad. Members of the NATIONAL RESEARCH COUNCIL receive their appointments from the president of the ACADEMY. They include representa­tives nominated by the major scientific and technical societies, repre­sentatives of the federal government, and a number of members at large. In addition, several thousand scientists and engineers take part in the activities of the research council through membership on its various boards and committees.

Receiving funds from both public and private sources, by contribution, grant, or contract, the ACADEMY and its RESEARCH COUNCIL thus work to stimulate research and its applications, to survey the broad possibilities of science, to promote effective utilization of the scientific and technical resources of the country, to serve the government, and to further the general interests of science.

The HIGHWAY RESEARCH BOARD was organized November 11, 1920, as an agency of the Division of Engineering and Industrial Research, one of the eight functional divisions of the NATIONAL RESEARCH COUNCIL. The BOARD is a cooperative organization of the highway technologists of America operating under the auspices of, the ACADEMY-COUNCIL and with the support of the several highway departments, the Bureau of Public Roads, and many other organizations interested in the development of highway transportation. The purposes of the BOARD are to encourage research and to provide a national clearinghouse and correlation service for research activities and information on highway administration and technology.

or L w i r t L i

REPORTS 66-70,72