Human Power

The Technical Journal of theInternational Human-Powered

Vehicle AssociationDavid Gordon Wilson, Editor

11 Bacon StreetWinchester, MA 01890-3808, USA

(617) 729-2203 (home)(617) 253-5121 (office)

IHPVAP.O. Box 51255

Indianapolis, IN 46251, USA(317) 876-9478

Marti DailyAdam Englund

Bruce RosenstielPaul MacCready

Alec BrooksGlen ColeGlen Ray

David Gordon WilsonAllan Abbott

Mike BurrowsMarti DailyPeter Ernst

Chet KyleGardner Martin

Matteo MartignoniDennis Taves

David Gordon Wilson

PresidentSecretaryTreasurerInternationalPresident

VP WaterVP LandVP AirExecutive VPBoard Members

Human Power is published quarterly bythe International Human-PoweredVehicle Association, Inc., a non-profitorganization devoted to the study andapplication of human muscular potentialto propel craft through the air, in thewater and on land. Membership informa-tion is available by sending a self-addressed, stamped business-sizedenvelope to:

IHPVAP.O. Box 51255Indianapolis, IN 46251-0255 USAMembers may purchase additional

copies of Human Power for $2.50 each.Nonmembers may purchase issues for$4.00 per copy.

Material in Human Power is copyrightedby the IHPVA. Unless copyrighted by theauthor(s), complete articles or representa-tive excerpts may be published elsewhereif full credit to the author(s) and theIHPVA is prominently given.

Special thanks to the authors, SabinaRataj, Marti Daily, and The ProfessionalEdge, without whom this issue would nothave been possible.

2 Human Power 7/2

EditorialsBefore the Take-offThe lead article in the current issue (vol. 5no. 3, October 1988) of HPV News, MarciaLowe's "Bicycles Have a PowerfulFuture", impressed me because it describ-ed the situation of human-poweredvehicles in terms that reminded me ofnonsmokers' rights a mere twenty yearsago. One can make a case that smokershave rights to smoke in certain circum-stances. But in those days, one could bean asthmatic in the hospital and havedoctors and nurses smoking over one, totake what might now seem like an ex-treme example but was then common-place. Virtually one hundred percent ofthe US population, a proportion thatincludes almost all smokers, would todayagree that it is wholly right that sensitivenonsmokers should be given some pro-tection from secondhand smoke. MarciaLowe's fifth paragraph struck me asanalogous to the smoking physiciansituation: "The World Bank, the mainsource of urban transit investment in thedeveloping world, published a 1985 studyon the Chinese transport sector that doesnot even mention the word bicycle, al-though the overwhelming majority oftrips in China's cities are made by bike.This is sadly typical of a policy environ-ment in which only motor vehicles aretaken seriously."

The protection of nonsmokersthroughout the world came aboutthrough the action of one man, an MITengineer-turned-lawyer named JohnBanzhaf, who petitioned the FederalCommunication Commission that theoverwhelming and unopposed advertis-ing by tobacco companies represented anunfair and unequal treatment of a con-

In This Issue-

Prone-Position Recumbent Bicyclesby Allan V. AbbottEditorials by David Gordon WilsonLetters to the EditorVibrational Stress on Cyclistsby Rainer PivitConstructing a Fairing Mold Plugby Greg TraylingA Simple Program for Propeller Per-formance Prediction by Theodor SchmidtReviewsFrontal Area Versus Surface Area-Prone or Supine? by Chester R. KyleSharpy-Cycle: An Experiment inPedal Power and Screw Propulsionby Philip ThielIndex of Human Power Articles

1

234

7

8

1313

18

19

troversial political position. The FCC

agreed, and the public service counter-advertising that Banzhaf brought aboutled rapidly to an astounding turnaroundin what had seemed for a century to betobacco's impregnable dominance.

The time is ripe for a similar transfor-mation in the apparently universal sanc-tion given to motor vehicles to clog ourcities, put smog into our air and to makeour whole way of life totally differentfrom that for which we were equipped bynature. Virtually every city in the"western" world is facing massive prob-lems of traffic congestion, to which thereseem no easy answers. Human-poweredvehicles are not the complete solution tothese problems, but they can play a vitalrole in a "kinder, gentler" transportationpattern. The technical advances that weseek in the IHPVA are helping to prepareordinary citizens to accept some futuretransformation in the present dominantrole of motor vehicles. All we need now isa Banzhaf to take the vital catalytic step.

The End of a Brave EffortBike Tech, "Bicycling Magazine's

newsletter for the technical enthusiast",will no longer be published after 1988.While it is easy to criticize a publishingempire for not continuing to back aworthy experiment, we should, rather,pay tribute to the support that RodalePress devoted for many years to some-thing that could not promise any financialreturn. Although Human Power and BikeTech should have been rivals, we havealways had friendly relations, withsomeone from the IHPVA board usuallyone of the contributing editors. Bike Techstarted out at a very high level under theeditorship of Crispin Miller, now pursu-ing his doctorate at MIT, and ended in thesame high tradition with Bruce Feldman,who will continue with Rodale as editorof its Mountain Bike publication. We salutethem and their colleagues, and wish themwell.

How-To-Build ArticlesIt is always good to appear respon-

sive. A letter from P. Michael Ditchen inthe October 1988 HPV News laments nothaving many "how-to" articles. I hopethat we will have several in this or laterissues of Human Power. Three factorscombined to bring this development. Itseemed, as it did to Michael Ditchen, to

be a good idea. I had seen several excel-lent articles in the NWHPVA newsletter(Seattle area) and in "hpv nieuws"(Holland) and had written for permissionto publish them in their entirety or in ashortened form. And, third, there hasbeen a seemingly sudden stoppage in theflow of articles coming in. Werner Stiffel'sconstruction plans required translationfrom German, and the indefatigable TheoSchmidt, who contributes materially toalmost every issue, volunteered fromSwitzerland. For the translation from theDutch, I asked Ellen Warner of OklahomaCity, where she rides an Avatar 1000. Herphotographs have appeared in previousissues. It seemed highly desirable that hermany talents be tapped for HIuman Power;accordingly, she and I were wed onDecember 30, 1988. How else may I showmy dedication to the cause of HPVs?

Probably not all of these pieces willappear in this issue. For an explanation ofthe uncertainty, read on.

How Human Power isPublished

Jean Seay has written somethingabout how she operates as editor of HPVNews, and I would like to do likewise fortHuman Power. Ideally I would be sentcontributions and, every three months, Iwould select the most scintillating for thenext issue. Actually, only a few contribu-tions come unsolicited. I phone and writeto many people to ask for papers andarticles (if there's a difference it is some-thing to do with technical or scientificcontent) and send a set of guidelines onhow we would like material to be writtenand reproduced. About a quarter of theseactually send something. (More estab-lished journals have room to publish onlya quarter or less of what is sent to them). Iedit everything that I believe needschanges to bring about more clarity orgrammar, trying to keep our overseasreaders especially in mind (many HPVenthusiasts write in a racy vernacular thatis wholly impenetrable by most non-Americans), and occasionally I mayshorten something that seems too long. Ifthere are major changes, I send a copyback to the author(s) to check that myalterations are acceptable, or I ask her/him to do some re-writing. When a majorcontribution (as distinct from a letter ornews item) comes in good time, I like tosend a copy to one or two people workingin the same area to ask for comments, andto give the author(s) an opportunity torespond. If a contribution is not on adiskette, Sabina Rataj, our generous suite

secretary at MIT, will usually be able totranscribe it when there are no other high-priority claims on her time. (Alas! Sabinais moving on, and I don't know how wewill manage for the next issue withouther help. I do some transcriptions myself,and some re-drawing of diagrams, but Iwould not like to have to do the wholeissue.)

I will do my editorial comments andreviews on weekends and evenings, andeventually send them to Marti Daily, whogets all the diskettes converted to aMacintosh format. Then she sends themto Kim Griesemer at The ProfessionalEdge for the production lay-up andcamera-ready copy. This is a major task.Kim has to arrange all these diversepieces and photographs and diagrams sothat we end up with exactly 20 or 24pages, and so that the issue is easy toread. Newspapers have lots of little"filler" pieces to make the task easier. Wehave very few. Kim often has to delay anarticle because it can't be made to fit. Shesometimes retranscribes a piece toachieve a more balanced layout. Eventu-ally a camera-ready copy is produced andsent to Marti, who takes it to a printingand distribution house. Very little wouldget done in the IHPVA without the helpof our intensely dedicated president.

What might seem to you to be asimple job takes many people a great dealof their spare time. Forgive us if some-times we slip in some respects.

A Human Power Index

In August I finished a longstandinggoal: to index all the articles that haveappeared in Human Power since it firstappeared ten years ago. It is reproducedon pages 19 and 20. Just after I finished it,Marti Daily sent me a categorized listingmade by an unknown (to me) hero. I willtry to incoporate this into an expandedindex later, and acknowledge her/himthen. -Dave Wilson 1I

Letters to the Editor

As the recent purchaser of a DeFelicerecumbent, I have wondered about thepossibilities of making some sort ofsimple enclosure that would improve airflow and exclude rain. It would have tobe simple enough for commuting service,and not appreciably increase the overalldimensions. Some sort of plastic sheetover a framework of wood strips starting

just in front of the front wheel would beeasy to construct, or it could be done withthin plywood as was the "Cafe Racer"(vol. 6/2), or a combination. Somequestions are these:

1. How detrimental is an openingto put feet down during stops intraffic?

2. Considering the benefits of theZzipper fairings, would it beworth the trouble to extend itfarther back than the rider'sknees or hips?

3. If carried all the way back past afairly wide seat and packagerack, how should it be termi-nated without going behind therear tire? I frequently carry itindoors by standing it up on itsrear wheel. Many cars havesome sort of turned-up fin acrossthe back to do something (pre-sumably beneficial) to theairflow when the rear of thebody does not taper to a line orpoint. For a vehicle taller than itis wide, could there be a verticalfin on each side to accomplishsomething similar? Can the bodybe left open at the rear, or shouldit be closed; if the latter, where isthe best location of an exhaustvent?

(On the topic of wheel-suspensionsystems for recumbents) I would like tooffer my experience with an alternative. Ipurchased my DeFelice after a short rideto determine the required frame size.However, as I became more confidentafter some weeks of riding it, I found thatI occasionally pedalled hard enough tostretch the nylon seat fabric sufficiently topush the straps against the rear tire (thefabric is in front of the seat-frame tubes,and the straps are behind). I decided Icould gain the required clearance byreplacing the fabric with a lawn-chair-style cord wrapping, but arranged in afigure-eight pattern around the frame sothat the cords crossed in the middle. Sincethe backrest must resist the force ofpedalling on a recumbent bike, I furtherstrengthened the seat by using polypro-pylene rope, which does not have theelasticity of nylon. For the lower part,which supports the major portion of therider's weight, however, I used nylon forits slight elasticity. The result was totallysatisfactory: the backrest stays where itshould, and the nylon "seat" allowsseveral inches of vertical movement of theridpr' hnbcl with renee-t tn h frmn A n"U" V Vei uuJ Ist I ruvt *V -1.. I - .. - . A- l

additional benefit is that the "seat" and(continued on page 15)

7/2 Human Power 3

Vibrational Stress on Cyclistsby Rainer Pivit

ABSTRACTThe vibrational stress on bicycle riders

with different bicycles and on different (cycletrack) surfaces was measured. Rough surfacesof typical West German city cycle tracksnearly always impair performance and evensometimes the health of the rider. Suspensionsystems can reduce vibrational stress.

INTRODUCTIONIn Oldenburg, a town of 140,000 in-

habitants in the lowlands of North WestGermany, bicycle traffic plays an impor-tant role in the traffic. In the inner cityabout 10% to 25% of the traffic is done bybicycles. All major streets have cycletracks on the sidewalks. The situation ofthe bicyclists is not as good as in theNetherlands but better than in mostGerman towns where only motorizedtraffic is promoted.

The traffic safety for the bicyclists inOldenburg is not better than in townswithout sidewalk cycle tracks. The ac-cidents happen at the crossings instead ofalong the street as in towns without cycletracks.

Most cycle tracks in Oldenburg aremade of concrete bricks because they arecheap and easily removeable for excava-tion. Riding on those surfaces is not verycomfortable, but bicyclists are forced bylaw to use them and are not allowed toride on the smoothly asphalted roadwaypavement.

As a small group of physicists at theUniversity of Oldenburg we are workingon bicycles and HPVs. In order to initiatea public discussion about cycle-trackquality we tried to quantify vibrationalstress on the rider. The method we used isstandardized by international ISO stand-ard 2631 and German VDI (VereinDeutscher Ingenieure = Society ofGerman Engineers) standard 2057. Thesestandards are mainly used on tractors andother machines where the operationalstaff is exposed to vibrations. Accordingto the standards the acceleration ismeasured at the interface with the rider.The acceleration is then filtered accordingto the frequency response of vibration ofthe human body. German VDI standardcalls the resulting effective value the K-Value. K-Values go linear with the accel-eration but differ with frequency. In theVDI Standard this K-Value--there is no

corresponding designation in the ISOCLA_,,I- , ... ... 1 - ALc..... LA -;

Ddranluaru-- useu to get exposure-Ime

limits for health or capacity of reaction orcomfort impaired. In the ISO standard thelimit of reduced comfort is identical to theVDI, the German limit of reduced capa-city of reaction is called exposure limit inISO standard, and is the upper limit.There is no limit of health impaired in theISO Standard; vibration should always bebelow the exposure limit (ISO) or limit ofreduced capacity of reaction (VDI).

The frequency response of (wo)manand the exposure-time limits are empiri-cal results. This method is very similar tothe standardized measurement of loud-ness. But (wo)man has a different fre-quency response concerning different di-rections and different parts of the humanbody. The hand-arm-system is, independ-ent of direction, most sensitive between 8and 16 Hz. The maximum sensitivity forvibration in the direction of the spinalcolumn of the body lies between 4 and 8Hz.

MEASUREMENTWe measured the acceleration at the

handlebar of the bicycle and at the under-side of the saddle in direction of the back-bone. The signals of the sensors wereamplified and encoded to a PCM-systemon the bicycle and sent to a data taperecorder in a nearby car by HF-telemetry.The data were evaluated with electricalfilters corresponding to the frequencyrating of the ISO and VDI standard.

Because the standards allow theinterpretation only of signals lastinglonger than 1 minute time we cannotmake statements about the effect of singlebad spots on cycle tracks like potholesand very bad transitions between cycletrack and driveway at crossings.

We carried out the measurement oneleven different surfaces:

* a very old pavement of irregular fieldstones (Hochhauser Str. flank),

· pavement of small (Werbachstr.) and* normal cobble-stones (Elisabethstr.),· very old brick-stone pavement with

stones on end (Hochhauser Str.middle)-this was an historic cycletrack as they were built in Oldenburgat the beginning of this century: 0.4m wide smoother brick-stone pave-ment at the middle of the street forbicyclists and field-stone pavement

for the other, slower vehicles at therest of the narrow street-,

* brick-stone pavement with old flatstones (Marschweg), and

* new (Damm),* concrete-stone pavement in a figure-

Y pattern, (Staugraben)-widelyused in the inner city area-and

* rectangular shaped (Carl-von-Ossietzky-Str. cycle track)-this kindof pavement is used on nearly allnew cycle tracks-,

* asphalted surfaces of cycle-trackquality (Freibad cycle track),

. country-road quality (Kuepkersweg)and

· highway quality (Carl-von-Ossietzky-Str. drive way).We repeated the measurement with

six different vehicles: a roadster bicycle,two touring bicycles, a Moulton bicycle,an OLF (Oldenburger Leichtfahrzeug =Oldenburg Lightweight Vehicle) and acar.

The roadster bike was similar to thetypical bicycles in the Netherlands and isthe type most commonly used in Old-enburg. The tires were 37-622 mm (28 x 1-3/8") at 320 kPa (45 PSI).The saddle haslarge pressure and tension springs. Thediamond-framed bicycle weighed 17 kg,the rider 80 kg.

Both touring bicycles had tires of thesize 28-622 mm (26 x 1-1/8") at 600 kPa(85 PSI) front and 700 kPa (100 PSI) rearand an 'anatomic' saddle without springs.The bicycles differ in the position of thehandlebar, wall thickness of CrMo steeltubes and weight. On no. 1 the rider'sarm had an angle of approximately 70degrees to horizontal, no. 2 was with 45degrees more at the standard position ontouring bikes. The wall thickness of thetubes of no. 2 were thinner (exact dimen-sions unknown). Bike no. 1 weighed 15 kgand its rider 80 kg, no. 2 14 kg and 72 Kg.

The Moulton bicycle was an AM 7with its 17" tires at 700 kPa (100 PSI). Thesuspension system is at front a weaklydampened steel spring and at rear arubber-block spring with internal damp-ing. Resonance frequency front and rear isapproximately 3 Hz. It had the samesaddle as the touring bicycles. Weight ofthe bike was 14 kg and of the rider 80 kg.

The OLF is a three-wheeled recum-bent prototype built by our bicycleresearch group (see Human Power,

4 Human Power 7/2

Constructing a Fairing Mold Plug byGregTrayling

This article is reprinted with permission fromthe North West Human Powered VehicleAssociation. It originally appeared in its Nov-Dec, 1986 newsletter.

If you're looking for an accurate andinexpensive method of building a sturdy,light-weight plug to make a moldedfairing, try the following method which Iused to make the fairing for the Paragon.

Start With the ProfileStart your design by drawing just the

profile that fits the rider and componentsof the vehicle. Cut out a template of thisprofile using a thin board, like eighth-inch (3mm) Masonite. Sand the edgesalong the cut to ensure a smooth curve.Draw vertical lines ten inches (250 mm)apart which will be stations for the per-pendicular supports of the plug. Alsodraw a horizontal reference line; I suggesta line indicating 200 mm from theground. Nail a wood stiffener on thesheet for reinforcing. Use thinner reinforc-ing near the tail where the form willtaper.

C.

0 o0 0o

Figure 1

Find the Width at Points Along theProfile

Next determine the shape of the fair-ing across its width. At such criticalpoints as the wheel axis and shoulders,cut out one side of the station templates.Figure 2 shows a front view of a shapewhich accommodates the wheel. Whendesigining, note that 3mm (1/8 inch) willbe added later by the surfacing layersover the whole plug.

Design While ConstructingMake intermediate stations using the

shape of the critical templates. One candesign while constructing, an advantageover constructing a preset design. Foruniformity, make all the templates curveinto a 90 ° angle at the top and bottom.Measure the template height from the

Front View

- Wheel

20

Figure 2profile. Trace two critical stations, asshown in Figure 3, and interpolate thestations between. Keep in mind the heightof the station from the profile. A NACAairfoil may be used to obtain the maxi-mum station width.

$50

C 34)

line ofation atark 50

10

so

signed-411-t

Outline of Stationat Mark 10

Inxermeu 1I Station atMark 30

Figure 3

When all templates for one side arefinished, make duplicates. I suggestclamping the duplicates together andsanding the edges to make identicalcurves.

Figure 4

Glue the station templates to the profile; Isuggest using a hot-glue gun. Add suchhorizontal supports as shown in Figure 5.Preview the overall shape, check thatcomponents fit, and adjust the design.

Fill the Form with FoamNext, finish the full form of the plug

with a blanket of polyurethane. First, tapecardboard strips a half-inch (13mm) fromthe edge and seal off to conserve foam.Mix the two parts of polyurethane pour-in-place foam. (Avoiding the vapors fromthis mix requires a proper respirator.) Just

Figure 5

as the mixture begins to foam, pour itbetween the plug and such a barrier as aplastic sheet held against the edges of thestations. Hold in place until foam sets,then peel barrier off. Fill all sections.

Figure 6

Smooth the form of the plug. Carefullysand any bulging foam down to thestation edges. If in doubt, sand to belowthe fairing shape desired, rather thanabove. Fill in gaps, holes, and depressionsby adding foam; simply paint on theliquid mix before foaming starts.

Apply a Hard SurfaceLastly, make the hard surface for

molding with fiberglass and filler. Applytwo to three layers of fiberglass mat withpolyester resin to entire plug. Let harden.Apply a layer of inexpensive talc resinfiller. Sand and repeat filler applicationuntil the plug is finished. Apply moldwax and release solution to ready theplug for molding.

As an alternative to foam, all of thesections may be filled with carefully bentand taped pieces of cardboard. Thefiberglass and talc filler layers give amplerigidity and accuracy.

The method described above yields astrong, light, and cheap plug. In addition,the fairing can be designed as the plug isbuilt. This saves considerable time invisualizing the rider and vehicle compo-nents from a scale drawing. All materialsand technical support can be found atyour local lumber supply and fiberglassshop.

Greg TraylingP.O. Box 4454Vancouver, BC V6B 3Z8CANADA O

7/2 Human Power 7

100 REM110 REM120 REM130 REM

Propeller Design 28.11.87By Theodor SchmidtInput data thru variables at beginning of programProgram runs from low RPM to top RPM given by R1and R2

140 REM in steps of "incr". Basic may take several minutes150 REM to work out first result.160 Diameter = 0.50 :REM (Meters)170 Ptch=0.66 :REM (Meters)180 U=1.5 :REM boat speed in m/s190 Rl=100 :REM (RPM)200 R2=600 :REM (RPM)210 Incr=10 :REM (RPM)220 Blades=2230 Header$="Y" :REM "Y" or "N" (prints out basic blade

parameters)240 Range$="Y" :REM "Y" or "N" (Limits top RPM to low blade

loadings)250 CH(1)=.075 :REM Chord at radial station 1 (near hub) in m.260 CH(2)=.080270 CH(3)=.087280 CH(4)=.091290 CH(5)=.091300 CH(6)=.087310 CH(7)=.080320 CH(8)=.070830 CH(9)=.055340 DIM FF(16,14)350 FOR K=1TO14360 FOR J=OTO15370 READ FF(,K)380 NEXT J390 NEXT K400 PI=3.14159410 CIRCUM=PI*DIAMETER420 OPEN,4:CMD1 :REM TRANSFERS OUTPUT TO PRINTER430 TA=ATN(PTCH/CIRCUM):TD=TA*57.296 :REM TIP

ANGLE440 SWPT AREA=PI*(DIAMETER/2)2450 FOR I=1TO9460 A(I)=CH(I)*DIAMETER/20* BLADES470 BETA(I)=ATN((PTCH/CIRCUM)/(I/10))480 A=A+A(I)490 NEXT I500 A=A+A(9)/4 :REM TOTAL BLADE AREA510 BAR=A/SWPT AREA :REM BLADE AREA RATIO520 AR=(DIAMETER/2)T2/A*BLADES :REM BLADE ASPECT

RATIO530 IF HEADER$="N'THEN 650540 PRINT "PROPELLER SIMULATION PROGRAM"550 PRINT " ":PRINT:PRINT "BLADE NUMBER=";BLADES560 PRINT"DIAMETER= ";DIAMETER; "M"570 PRINT "PITCH = ";PTCH;"M"580 PRINT "SWEPT AREA = ";INT(SWPT AREA*10000+0.5)/

10000;"SQ M"590 PRINT "BLADE AREA RATIO = ";INT (BAR*10000+0.5)/

10000600 PRINT "BLADE ASPECT RATIO- ";INT(AR*1000+0.5)/100610 PRINT 'TIP ANGLE= ";INT(TD*100+0.5)/100; "DEGREES"620 PRINT "STATION CHORD (M) ANGLE (DEGREES)"630 FOR N=1TO9640 PRINTN;SPC(9);CH(N);SPC(9);INT(BETA(N)*5729.6+0.5)/

100:NEXT N;PRINT

650660670680690700

PRINT DIA PITCH BT SPD PR SPD P IN P OUT ETA";PRINT"ETA F THRUST CL(5) SLIP'PRINT"(M) (M) (M/S) (RPM) (W) (W) (%) (%) (N)"R3=R1;R4=R2FOR RR=R1TOR2 STEP INCRVR=CIRCUM*RR/60

710 I=1720 DELTA(I)=ATN(U/(VR*(I/10)))730 ALPHA(I)=BETA(I)-DELTA(I) :REM ANGLE OF INCI-

DENCE AT BLADE ELEMENT740 IF ALPHA(I)<-0.1 THEN R3=RR+INCR:GOTO770 :REM

LIMITS PROGRAM TO POSITIVE LIFT750 IF ALPHA(I)>.26 THEN R=4=RR:GOTO780 :REM RE-

STRICTS BLADE LOADING760 IF 1<8.5 THEN I=I+1 :GOTO720770 NEXT RR780 IF RANGE$="N"THEN R4=R2790 FOR RPM=R3TOR4 STEP INCR800 VR=CIRCUM*RPM/60810 PP=0:PW=0:T=0 :REM POWER IN, POWER OUT, THRUST820 UR=U*(1+Q) :REM SPEED THRU DISC, Q IS SLIP FACTOR830 FOR I=1TO9840 UR(I)=U*(1+Q(I))850 VR(I)=VR*(I/10)860 W(I)=SQR(UR(I)t2+VR(I)t2) :REM RESULTANT SPEED AT

BLADE SEGMENT870 DELTA(I)=ATN(UR(I)/VR(I))880 ALPHA(I)=BETA(I)-DELTA(I)890 CL(I)=ALPHA(I)*5.75/(1+2/AR)+0.35 :REM COEFFICIENT

OF LIFT900 IF CL(I)<0 THEN GOTO1470910 RE(I)=1E6*W(I)*CH(I) :REM REYNOLD'S NUMBER (for air

replace 1E6 with 7E5)920 X=ABS(INT)(10*CL(I)+0.5))930 IF X>15THEN X=15940 IF RE(I)<45000THEN Y=1:GOTO1000950 IF RE(I)<105000THEN Y=INT(RE(I)/1E4-2.5):GOTO1000960 IF RE(I)<212500THEN=INT(RE(I)/2.5E4+3.5):GOTO1000970 IF RE(I)<2E6THEN Y=12:GOTO1000980 IF RE(I)<4E6THEN Y=13:GOTO1000990 Y=141000 CD(I)=FF(X,Y)/1000 :REM PROFILE COEFFICIENT OF

DRAG1010 IF CL(I)>1.2 THEN CL(I)=1.2 :REM PATHETIC ATTEMPT

TO SIMULATE APPROACHING STALL1020 ID(I)=CL(I)T2/(PI*AR) :REM INDUCED DRAG*1030L(I)--500*A(I)*CL(I)*W(I)T2 :REM LIFT*1040D(I)--500*A(I)*(CD(I)+ID(I))*W(I)t2 :REM DRAG1050 T(I)=L(I)*COS(DE(I))-D(I)*SIN(DE(I)) :REM THRUST1060 F(I)=L(I)*SIN(DE(I))+D(I)*COS(DE(I)) :REM LATERAL

FORCE1070 PP(I)=F(I)*VR(I) :REM POWER IN1080 PW(I)=T(I)*U :REM POWER OUT1090 ETA(I)=PW(I)/PP(I) :REM EFFICIENCY*1100 CT(I)=T(I)/(500*DI*(I /10)*PI*U*U*DI/20) :REM COEFFI-

CIENT OF THRUST1110 C2(I)=Q(I)*4*(1+Q(I)) :REM ALSO COEFFICIENT OF

THRUST1120 EF(I)=2/(1+SQR(1+CT(I))) :REM FROUDE EFFICIENCY-I ,n r' _.1 IrT 1

1 IOU ,.lU=L / VtL1)-1

* For salt water, replace 500 with 512. For air, replace 500 with0.625

7/2 Human Power 9

1140 IF ABS(C2(I)/CT(I)-1)>0.05 THEN 8401150 T=T+T(I)1160 PP=PP+PP(I)1170 PW=PW+PW(I)1180 NEXT I1190 ETA+PW/PP*1200CT=T/(500*SW*U*U)1210 EF=2/(l+SQR(1+CT))1220 Q=1/EF-11230 C2=4*Q*(1+Q)1240 UJ=U*(1+2*Q)1250 P$=RIGHT$(STR$(INT(DIAMETER*101)/100),51260 PRINTP$;SPC(7-LEN(P$));1270 P$=RIGHT$(STR$(INT(Pr*101)/100),5)1280 PRINTP$;SPC(7-LEN)(P$));1290 P$=RIGHT$(STR$(INT(U*100)/100),5)1300 PRINTP$;SPC(7-LEN(P$));1310 P$=RIGHT$(STR$(INT(RPM)),5)1320 PRINTP$;SPC(7-LEN(P$));1330 P$=RIGHT$(STR$(INT(PP+0.5)),5)1340 PRINTP$;SPC(7-LEN(P$));1350 P$=RIGHT$(STR$(INT(PW+0.5)),5)1360 PRINTP$;SPC(8-LEN(P$));1370 P$=RIGHT$(STR$(INT(ETA*100+0.5)),5)1380 PRINTP$;SPC(7-LEN(P$));1390 P$=RIGHT$(STR$(INT(EF*100+0.5)),5)1400 PRINTP$;SPC(8-LEN(P$));1410 P$=RIGHT$(STR$(INT(T+0.5)),5)1420 PRINTP$;SPC(7-LEN(P$));1430 P$=RIGHT$(STR$(INT(CL(5)*100)/1 00),5)1440 PRINTP$;SPC(6-LEN(P$));1450 P$=RIGHT$(STR$(INT(Q*1 000+0.5) /1000),6)1460 PRINTP$

1470 NEXT RPM1480 PRINT#1:CLOSE 1 :REM CLOSES FILE TO PRINTER1490 REM THE FOLLOWING VALUES ARE READ INTO THE

ARRAY FF AND1500 REM REPRESENT CD AS A FUNCTION OF CL AND RE1510 DATA25,23,27,50,70,80,80,80,75,70,60,50,50,200,1000,1000

(RE<45000)1520 DATA24,22,25,40,50,55,57,58,55,50,45,42,46,180,1000,1000

(RE=50000)1530 DATA23,21,23,35,40,46,46,46,46,46,42,38,45,150,800,1000

(RE=60000)1540 DATA22,21,22,31,35,39,39,39,39,39,37,35,41,140,700,1000

(RE=70000)1550 DATA22,21,21,27,30,33,33,33,33,33,32,31,37,130,700,1000

(RE=80000)1560 DATA21,21,21,23,25,27,27,27,27,27,27,27,33,120,600,1000

(RE=90000)1570 DATA20,20,20,20,19.9,19.5,19,19,19.1,19.5,20.2,23,30,100,600,

1000 (RE=100000)1580 DATA19,16.8,18.6,18.3,18,17.5,17.2,17.3,17.8,18.3,19.2,21,28,84,

600,1000 (RE=125000)1590 DATA18,17.7,17.2,16.5,15.6,15,14.6,14.8,15.3,16.2,17.3,20,25,

80,500,1000 (RE=150000)1600 DATA17.5,16.3,15,13.6,12.7,12,12,12.4,13.6,14.6,16,18,24,60,

400,1000 (RE=175000)1610 DATA1 7,14.5,12,10.2,9.5,9.3,9.4,9.8,10.8,12,13.8,16,21,42,84,

168 (RE=200000)1620 DATA12,10.3,9.3,8.6,8.3,8,8,8.3,9,10,11.1,13,15.5,20,40,80

(RE<2 106)1630 DATA7,7,7,7,7,7,7,7.1,7.5,8,8.8,10,12,15,20,30 (RE<4 10 )1640 DATA6.2,6.2,6.2,6.2,6.2,6.3,6.4,6.6,6.9,7.3,8,9,10.1,1 2,14,17

(RE<4 106)

Propeller data taken fromHUMAN POWER

page 11 vol. 6 no. 2 (Summer, 1987)*compare with results In Table 1, page 11

PROPELLER SIMULRTIOH PROGRAM

TIrMETER = .4 M Bl;--h = .44

iE T RE = .1257 SQ BLiE ARER RMTIO = .2821BLDE RASPECT RRTIO s 3.15TiP AHGLE = 2.11 DEGREESSTfTION CHORD CM] ARNGLE [DEGREESi

1 .o 0 .0834 62.842 0 .0894 52.553 ,? 9 .01 44.714 . .0874 38.33 Rjq i ortc6 .1, .0698 28.98 5 . B . 33.j7 .il .0569 25.538 . 4 .8404 22.679 .1 .8293 21.42

DIP PITCH BT SPD PR SPD P IN P OT ETA ETR F THRUST a(s) C

[Mi [M] IM/S] [RPM] C[W) W] %1 [1% N] (S1.4 .46 .5 188 11 7 62 84 14 .74 .188.4 .46 .5 118 16 9 59 81 18 .82 .237.4 .46 .5 128 21 12 5 78 23 .87 .287.4 .46 .5 130 27 14 53 75 29 .S2 .339.4 .46 .s 148 34 17 58 72 34 .96 .392.4 .46 .5 158 43 20 48 69 40 .99 .445.4 .46 .s 168 52 24 45 67 47 1.82 .5.4 .46 .5 178 63 27 43 64 54 1.e4 .55.4 .46 .5 188 77 30 39 63 68 i.04 .595

1.4 .46 .s 19e 91 33 36 61 66 :. .643,4 S .5 200 106 37 ,s 59 74 100 .697

.4 .46 .3 218 126 41 32 57 82 1.09 .746

.4 .46 .s 228 151 44 29 56 89 1.11 .79

.4 .46 .5 238 161 l1 31 54 1ol 1.12 .864

.4 .46 .5 240 183 56 30 52 1!1 1.13 .92

.4 .46 .5 258 206 61 29 51 121 1.14 .977

.4 .46 .81

.4 .46 = .01

.4 .46 ,.01

.4 .46 .81

.4 .46 .01

.4 .46 .1

.4 .46 -=.81

.4 .46 -.81

100 19120 32140 51

168 76

18 107200 111220 144

248 173

0O8801

I1

1

1 4 19 1.2 27.3341 3 28 1.2 32.9161 3 38 1.2 38.4851 2 50 1.2 44.8811 2 63 1.2 49.6661 2 82 1.2 36.771 2 1 100 .2 62.563I . 121 1.Z 69.012

Dlf P.TCH i-SFF F i t,[M] [M] [M/S,]; [EPMV :KJ

.4 .46 Z 220 l

.4 .46 Z.2 - 27

.4 .46 2. 240 46.4 .46 L.2 250 65.4 .46 2.2 260 88

.4 .46 2.2 270 113

.4 .46 2.2 28e 19

.4 .46 .- 29 168,* .4 2.2 300 19.4 46 2.2 310 . .46 _. _ _. t.4 .46 2.2 33 307.4 .46 2.2 348 348.4 .46 2.2 350 392.4 .46 2.2 368 438

.4 .46 2.2 370 488

.4 .46 2.2 388 340

.4 .46 2.2 390 596

.4 .46 2.2 480 655

.4 .46 2.2 4"a 717.4 .46 2.2 420 782

.4 .46 2.2 438 851

.4 .46 2.2 440 923

.4 .46 2.2 4se 998

.4 .46 2.2 270 113

.4 .46 2.2 271 116

.4 .46 2.2 272 118

.4 .46 2.2 273 121

.4 .46 2.2 274 123

.4 .46 2.2 275 126¢ .4 .46 2.2 276 129

4 .46 2.b Z I'l 132.4 .46 2.2 278 134.4 .46 2.2 279 137.4 .46 2.2 280 148

.4 .46 1 188 1

.4 .46 1 11l 5

.4 .46 1 120 10

.4 .46 1 130 15

.4 .46 1 140 22

.4 .46 1 138 38

.4 .46 1 168 39

.4 .46 1 170 49

.4 .46 1 188e 60

.4 .46 1 198 73

.4 .46 1 280 87

f1¢.4 .46 1 210 183.4 .46 1 2ZZ 121

.4 .46 1 230 140

.4 .46 1 240 162

.4 .46 1 250 185

1 3

547494:!5

138

6-

236265294324355386421455491527565603643

74 92 1

-75 91 4

74 70 :47EZ _. .a. 9- 3373 9 1 672 87 176SZ 9 6771 85 19178 87 207

64 84 22376 6 1217 91 13474 se 1 4773 es 16272 Bs 17671 85 ISI70 87 27

68 86 22367 86 24066 85 25765 84 27464 83 292

94 83 97 4397 84 97 4499 83 97 45101 83 96 46

103 83 96 47

185 B3 96 48107 83 96 491 9 83 96 58111 83 96 51114 83 96 52116 83 96 03

% T8 13 100 0

4 72 99 48 78 97 812 78 96 1217 77 94 17

22 75 92 2228 73 91 2835 71 89 3541 69 87 4149 67 86 4956 65 84 56

65 63 82 6574 61 81 74

83 59 79 8393 57 78 93183 56 76 103

10 Human Power 7/2

.e-- :E-O?

.8 - E-el

.1L3 .c13

.L4 .32728 .03443 041

3 091.3- .Q49.,4 .35

.5 .a132.5'3 ,091

.56 .14.5 .505

.61 .119

.63 .1279

.75 .139

.67 .143

.71 .169

.73 .179

.75 .19.76 .2

.28 .834.29 .035,29 .036

.3 .036

.3 .037

31 ,3s.31 .~.31 .630

.32 .04

.32 .041

.33 .842

.62 IE-03.15 .014

.26 .029

.35 .84s

.43 .863

.51 .882

.57 .102

.62 .122

.67 .144

.71 .166

.74 .189

.79 .213

.81 .237

.83 .261

.86 .286

.88 .312

-

Prone-Position RecumbentBicycles(continued from page 1)

categories of items on the questionnairepertained either to their "most successfulprone-position HPV design" or to "prone-position HPVs in general". Items in eachcategory were further divided into areas ofcomfort, power, and control, and in eachcase, respondents were asked to compareprone recumbents to conventional racingbicycles. A five-point scale was used foreach specific item with "1" being poor, "3"being the same, and "5" being excellent ascompared with a conventional racing bi-cycle. Respondents were asked also tocomment on each of the above areas and todiscuss the advantages and disadvantagesof the prone position. The author has builtand ridden four prone recumbent bicyclesand also completed a questionnaire. Ninecompleted questionnaires were received.Means and ranges for each of the scoredresponses were calculated and commentsrelevant to each item are included in theresults.

RESULTSThe means and ranges of ratings for

each item are included in Table 1. Generalcomfort received a mean rating of 1.9 (ascompared to a standard 3.0 rating for aconventional bicycle). All components ofcomfort, including visibility were gen-erally rated as inferior to a conventionalbicycle. Most respondents commented onthe need for comfortable supports rigidlyattached to the frame for the pelvis andshoulders. All used toe clips to support thefeet. Some used a padded support for thechin. One used elastic supports for theknees. Several respondents commented onthe rider's difficulty in turning his headwhile in this position to see directly to therear.

Power generated in the prone positionwas generally rated as slightly inferior tothat in the conventional position. Therewas, however, a great deal of variability inthe opinions. Brief ergometry testing byChet Kyle showed long-term power to bean average of 8% less than the conven-tional position. While most respondentsagreed that long-term power was slightlydecreased, the respondent with the mostexperience (GJ) felt that his ability toproduce prolonged power in the proneposition was excellent, and that long uphillclimbs were no more exhausting than on astandard bicycle. Most felt that peakpower was slightly better than in the

Table 1Means and ranges of ratings of prone-position human-powered vehiclesby designers and riders*

Category Own Best Machine Prone Machinesin General

ComfortGeneral comfort 1.9 (mean)(1-4)(range)** 1.9 (1-4)Head/neck comfort 1.4 (1-3) 1.5 (1-4)Leg comfort 2.4 (1-4) 2.4 (1-4)Visibility 1.8 (1-2) 2.1 (1-3)

PowerPeak (short-term) 3.5 (2-5) 2.3 (2-5)Long-term power 2.4 (1-5) 2.5 (1-5)Hill-climbing power 2.3 (1-4) 2.3 (1-5)

ControlControl when turningcorners 2.2 (1-3) 2.3 (2-3)

Control on roughterrain 1.5 (1-2) 1.4 (1-2)

* number of respondents = 9** rating scale: 1 = poor, 3 = same as conventional racing bicycle,

5 = excellent

conventional position and that having theshoulders against solid supports aided inthe production of peak power. It wasnoted that training in the prone positionis necessary to improve efficiency in thisposition. The inability to change positionswhile in the prone position was noted tobe a disadvantage as compared to theconventional position where the rider canstand for hill climbing, stretching, etc.Two of the respondents utilized the proneposition to facilitate hand and foot powerto increase peak power for short periodsof time.

Control was rated at a level similar tocomfort, moderately inferior to the con-ventional cycling position. Two of therespondents built three or four-wheeledmachines and did not comment on con-trol. Two of the respondents with a greatdeal of prone bicycling experience (GJand CD) felt that cornering ability of aproperly designed prone recumbent wasequal to that of a conventional bicycle. Allof the respondents used low-slung, long-wheelbase designs and stated that thelong wheelbase and low ground clearancewere disadvantages in some maneuver-ing situations. Control over rough terrainwas a consistent problem.

All of the respondents cited lowfrontal area and the potentially lowassociated aerodynamic drag as the chief

advantage of the prone recumbent posi-tion. This position allows the possibilityof a simple, lightweight vehicle designutilizing standard bicycle parts (no longchain paths, etc.). Two of the respondentsfelt that the prone position felt natural,powerful and aggressive. Most respon-dents felt that it is possible to producemore peak, short-term power in the proneposition.

Comments about disadvantages ofthe prone position varied greatly anddepended upon the respondent's experi-ence and type of machine. Several com-ments were made about the potentialdanger in a head-first, "head-on" colli-sion. Respondents frequently noted thedisadvantages in maneuvering their long-wheelbase, low-ground-clearance pronemachines. The low profile of thesemachines was also noted to make themhazardous when on the road with auto-mobiles. Reduced comfort, poor visibility,inability to use "body English" in balanc-ing, and inability to "post" to avoid shockinput were also noted by some respon-dents.

DISCUSSIONAll but one of the respondents de-

signed their prone recumbent machinesprimarily for top-speed competition.Thus, their experience and opinions must

7/2 Human Power 11

speed land vehicle might benefit from thelow frontal area and potentially low aero-dynamic drag which are possible with theprone position. The prone position mightalso be best for human-powered subma-rines because drag problems are multi-plied many times under water. The over-all combined opinions as summarized inTable 1 suggest, however, that the proneposition is inferior to the conventionalbicycling position in nearly every way. Itshould be kept in mind that those indi-viduals who were the most enthusiasticabout the prone position for human-powered vehicles were also the individu-als with the most experience and greatestsuccess with prone recumbents. Futuredesigners considering the use of theprone position for human-poweredvehicles should pay particular attentionto the successes of these experienceddesigners.

The author wishes to acknowledgethe following individuals who contrib-uted their time, experience and knowl-edge to this paper: Steve Ball, ColeDalton, Greg Johnson, Chester Kyle, FredMarkham, Gardner Martin, Paul VanValkenburg, and Kurt Wold.

Allan V. AbbottP.O. Box AAIdylwild, CA 92349

Allan Abbott was the first president of theIHPVA; he held the paced bicycle speed recorduntil recently; offered the Abbott prize for thefirst IIPV to exceed 55 mph; developed theFlying Fish hydrofoil with Alec Brooks, and isa physician.-ed. Li

ReviewsAs reported in the editorial com-

ments, Bike Tech ceasing publication--orperhaps has already done so (as ofDecember 1988). There have been threeissues-April, June and August, 1988,since our last review. In April there werearticles on do-it-yourself grease fittings,the Campagnolo Synchro shifter, a shortnote on human power that continues inthe next issues, an article on clincher tires(the successor, on mountain-bike tires,appears in June), and a piece by editorBruce Feldman on the Long Beach show:"Steel springs back". He refers to bikeframes. I for one am relieved. Aluminum-alloy frames, and particularly forks, scareme if they are subjected to hard use.

(continued on page 16)

Frontal Area Versus SurfaceArea-Prone or Supine?by Chester R. Kyle

David Gordon Wilson asked me tocomment on a question posed by AllanAbbott's survey of prone recumbentdesigners. The question is the relativeimportance of frontal area versus surfacearea in achieving low aerodynamic drag.Although I can't answer this exactly,some discussion should help clarify it.

Since 1975, when competitors sys-tematically began trying to build theworld's fastest human-powered vehicle,various schemes have been used toachieve the lowest aerodynamic dragpossible and the highest speed. To do thisHPV builders have generally employedefficient aerodynamic shapes and mini-mum frontal area. The belief is common

VEHICLES TESTED GIVING THE RESULTS IN FIGURE 1

1 Paul Van Valkenbu2

3

4

that minimum frontal area will produceminimum aerodynamic drag. This is trueup to a point. Hoerner (Aerodynamic Drag,1965, p. 6-16), reports that with symmetricstreamlined airship shapes, the optimumlength-to-fineness ratio is about 5. Withvery careful design of the profile, othersfind that this ratio can be from 3.5 to 5.This means that as the ratio of the lengthto width increases, the skin frictionbecomes more significant compared topressure drag, until an optimum occurswithin a certain family of shapes.

The proximity of the ground planecomplicates the matter, but it is obviousthat by increasing length, larger surfaceareas will sooner or later cause an in-

rgh racing bicycle, bare.. . .. .with

Aeroshell fairing and bottom skirt

Mario Palombo tricycle, rear steering,no fairing

". . ... . faired but

MAX.SPEEDmph

46.51

(20.79 m/s)

exposed rear wheels 44.38 (19.84)Chester Kyle standard racing bicycle, faired 46.46 (20.77)O

* Paul Van Valkenburgh prone quadracycle,+ hand-and-foot powered

, - )0= -_

A Steve Ball prone tricycle,hand-and-foot powered

=Co°

linear-actioi

49.38(22.07 m/s)

54.69

(24.45 m/s)

U Bill Watson supine bicycle 46.12

i t --a (20.62 m/s)

J Eric Edwards supine tricycle, rear-steering,oval pedal travel 50.72

.=C) Z (22.67 m/s)0 - ,

The coast-down tests, 1977-1984, involved two streamlined bicycles,two prone recumbents, andthree supine recumbents.

CRK/DGW 89.01

7/2 Human Power 13

-S

.4

I2

65 tO 15 20i ,

S 10

5 PEE

1 Van Valkennurgh racing bicycle, bare, 19772 " Aeroshell

faring and botomn skirt, 1977L " prone quadracyle, 1977

19783 Palombo supine tricycle, bare, 1976

wit fairing, exposed heels, 1976bicycle, streamlined

sus supine tricycle, 1984bicycle, 1978

.y prone tricycle. 1984

AST- TS

uT-eWN T vehles,

,uan-poered ehicles.to.a. rag versus speea.

Ik5s r r

25 30 35 40 45

5 etLj/s,,e 20

D C.8eYE I 12k/ ' Do 0119

Figure 1. Coast-down tests, streamlined human-powered vehicles, total drag versus speed.

crease in drag, no matter how small thefrontal area. Actually the most successfulHPVs today are relatively short. GardnerMartin's Gold Rush, (a supine bicycle andthe curent world-record holder- 65.49MPH), is only 8 feet long. It has a frontalarea of 5 square feet, and an equivalentlength-to width ratio of only 3.2. Table 1gives the dimensions of the Gold Rushplus Steve Ball's tricycle Dragonfly, (aprone recumbent with hand and footpower and linear pedal travel, topspeed-54.7 MPH), Allan Abbott's pronebicycle (50.44 MPH), and several others.Five of them are also listed in Figure 1.

From the table, it is apparent thatthere can be a considerable advantage to aprone recumbent in achieveing low fron-tal area compared to a more uprightsupine bicycle. However as to actualcomparative drag, the advantage isquestionable.

Using high-speed coast-down testsbetween 1976 and 1984, I measured thetotal drag of seven streamlined HPVs.The measurements were done on smoothasphalt or concrete pavement (the LosAlamitos Naval Air Station Runway andthe San Gabriel River Channel, Califor-nia). The results are shown in Figure 1.With a coast-down test, all components ofdrag are summed including rolling-bear-ing friction, rolling-tire friction, and airdrag. The curves show that some of themachines had a very high rolling drag(extrapolate the curves to zero speed). Forexample, the rolling drag of the Palombotricycle is about double that of the rest,probably due to a sticky sealed bearing,or a gummy freewheel. Also, the curvefor Steve Ball's Dragonfly shows a higherrolling friction than the others. This isprobably due to a friction-clutch mecha-nism used in the linear drive.

If the rolling friction is disregarded,then the Dragonfly has the lowest aero-dynamic drag of any of the vehicles meas-ured. The highest would be the Palombosupine tricycle closely followed by theVanValkenburgh standard bicycle withthe Aeroshell fairing. The other fourmachines are approximately equal. Coast-down tests therefore support the conclu-sion that a prone machine can have a verylow aerodynamic drag.

However, a well-designed supinetricycle such as Don Witte's Allegro (62.98MPH) probably has as low a frontal areaas the Dragonfly, and it is probably some-what shorter as well. Abbott's prone bi-cycle however holds the record for mini-mum frontal area at only 3.3 square feet.Even though Abbott's top speed was low-er than some of the others, all of the othervehicles mentioned were ridden bynationally ranked bicycle racers. Abbottrode his own vehicle, so it is unclear whatthe potential of his machine really is.

Besides using the prone position toachieve minimum frontal area, designershave often resorted to linear pedal travel.Because of the increased complexity oflinear mechanisms the lower mechanicalefficiency could hamper speed. No onehas measured the mechanical or biomech-anical efficiency of linear-pedal-travelmechanisms versus the conventionalcircular motion, so their effect on speed isuncertain.

Another strategy to minimize frontalarea with tricycles is to decrease the re-quired width between the paired wheels.Two schemes have been used. EricEdward's Pegasus drives the two frontwheels and uses rear-wheel steering. Hesolved the rear-steering stability problemby using negative trail, dampeners, and avery limited steering angle. Don Witte'sAllegro reversed this plan by combining

Table 1

Vehicle Length Width Height Frontal Area L/W

Gold Rush SupineAbbott ProneDragonfly ProneVanValkenburgh

Standard BikeKyle Standard BikePalombo SupineTricycle

VanValkenburghProne

8 feet12.5 feet10.2 feet

8.3 feet

19 inches18 inches22 inches

20 inches

51 inches31 inches30 inches

62 inches

5.0 square feet3.3 square feet4.4 square feet

7.3 square feet7.6 square feet

5.0 square feet

5.0 square feet

14 Human Power 7/2

ES-

20

3

2

IS0

U

3.26.14.3

5

the drive and steering in the single frontwheel, and by allowing the rear pair tofreewheel.

Practical results have shown that aslightly higher frontal area does notnecessarily result in a higher drag. Thetwo fastest HPVs in the world are supinebicycles, Gardner Martin's Gold Rush,65.49 MPH; and Tim Brummer's Light-ning X2, 64.19 MPH).

Probably the breakthrough that ledto these high-speed supine bicycles wasthe development of what could be calledthe Land Shark-Nosey Ferret-Lightning-Infinity-Gold Rush shape. Except for theLand Shark, each of the above vehicleshas won the Speed Championships. Thisshape consists of a low, narrow, roundednose, tapering upward and back andreaching the widest point at the rider'sshoulders. From this point, the contourtapers back to a sharp trailing edge. Asfar as I know, this shape was not pat-terned on any wind tunnel or theoreticalmodel, but was based on logic and eye-ball intuition. The first of this generationwas probably Danny Pavish's Land Sharkin 1980, using the Easy Racer bicycle as abase. Over the years, the shape has beenrefined by numerous designers until it issuperbly efficient in many forms. Accord-ing to Danny Pavish, it leads to laminarflow over the forward part of the fairing,minimizing air-friction drag.

One conclusion that can be drawnfrom the above discussion is that frontalarea is not the most important factor indesigning a successful human-poweredvehicle. Total aerodynamic drag, stability,visibility, biomechanical practicality andefficiency, mechanical efficiency, and lowweight are some factors that can be ofequal importance. It is a pity that moreexperimental information is not available;however, the typical designer is often toobusy building and testing, and can't oftenafford the time to write about her/hisobservations and findings. For thisreason, Allan Abbott's article is verymuch appreciated. I hope that it will leadto others of a similar nature.

Chester R. Kyle9539 Old Stage Rd.Weed, CA 96094 O

Letters to the Editor(continued from page 3)

the seat frame as the one-piece fabric did.Theoretically, the unsprung weight is

much greater in this case. In practice, thetotal weight of a bike frame is much lessthat that of a car, or even a motorcycle,which has a rear suspension similar to theMoulton upright bike, the German Radiusrecumbent, and a similar U.S.-made one.While it would not be possible to suspendthe seat of an upright bike independentlyof the pedals, the bounce motion of therecumbent rider is perpendicular to thedirection of pedalling, analogous to theswinging rear suspension that pivotsapproximately around the center of thedriving sprocket. When the front wheelhits a bump, the entire bike pivots aroundthe rear axle, but with the nylon-rope seatthe inertia of the rider's body allows it tofollow later, probably after the wheel haspassed over the bump and returnedalmost to its previous road level. Thus thebody is not required to deflect to theextent that it would on a more rigid seat(the rope seat has considerably moreflexibility than the original fabric, whichin turn is much more flexible than thecustomary bike saddle). A similar seriesof reactions follows as the rear wheel thenhits the bump, except that the bike nowpivots around the front axle.

I do not know how effective such aseat would be on a tricycle, where theouter wheels can impart both roll andpitch to the frame unless they are sus-pended independently, as on that in HPvol.7/1. That vehicle is intriguing as amechanical engineering project, but incomparison to my suspension of the rider,I wonder if it is worth the additionalweight and complexity. One must re-member that in a car, the body constitutesthe major portion of the sprung weight,with two passengers in a small carcomprising some 15% of the total, where-as a bicycle is just the opposite-the bikealone is a similar fraction of the weight ofthe vehicle plus rider. Isolating the bodyfrom the wheels of a car allows much ofthe mass to move less than the wheels.

On the other hand, the controlledflexibility of the trike shown may reducethe required strength of the supportmembers because they allow the wheeldeflection by a bump to be dissipatedthrough compression of the spring ele-ment, and thus do not need the rigidity totransmit the motion to the rider (comparethe dimensions of the A-arms of thelightweight commuting vehicle in HPvol.7/1 with the si7P nf th tnn ancl nwn

tubes of a diamond frame). A completeengineering study of this aspect of

complexity vs. weight would be veryinteresting.

Milford S. Brown7308 Gladys AvenueEl Cerrito, CA 94530

(I combined two letters here -ed.)

This is a late comment on RamondoSpinnetti's article, (vol. 6/3), because Iwas busy in Greece on the Daedalus crew.

First, I agree with the concern expres-sed by Prof. Bussolari in his commentsthat it is hard to draw conclusions from asingle-subject experiment, especiallywhen the test subject is the experimenterand author of the paper. It would be veryuseful to get more data with some otherriders on the apparatus.

I will, however, disagree to an extentwith (Steve) Bussolari's concerns aboutthe differences in rider position. I feel thatit is quite valid to choose any suitableposition for the reverse-pedalling tests,with the possible restriction that it bepractical for actual bicycle applications(which this position clearly must be,based on the photograph of the author'sbicycle in issue 7/1). There is no reason toarbitrarily restrict the reverse tests to aposition that may be unsuitable. On theother side of the issue, it could conceiva-bly be that better results would be obtain-ed for forward pedalling using somesuperior seating position that has eludedframe designers, but the author certainlycannot be faulted for using the "stan-dard" position as his basis of comparison.

The biggest problem that I find,however, has to do with the lack of footrestraint on the test apparatus. If thephotographs accurately represent the testsetup, then it would seem that the bi-cycles had no toe clips. The force-vs.-crank-angle graph would seem to beconsistent with this. (The bicycle in thephoto in issue 7/1 also seems not to havetoeclips.) It would seem quite possiblethat with no foot restraint, greater powercould be obtained with a reverse ped-alling motion; however, almost allapplications that would attempt to extractmaximum power would use some form oftoe clips, and I feel that toe clips (espe-cially if used with cleated shoes) couldhave a dramatic effect on the data, as theyallow the rider to pedal "in circles",rather than just pushing down on thepedals.

I have wondered about the efficiencyof reverse pedalling for some time, and in

7/2 Human Power 15

backrest portions are not connected; thusthe vertical movements of the rider do notcause the backrest covering to slide down

..... ...... ~ v.- .~ L.. .- - -,

SHARPY- CYCLELENGTH GL0 I

BEAM, A, 3 LGD AFT-, wU L O-3ZMAT7 Eat t'-7U

__i -, f--- -r- - -i- '_- 5EC71ONAL ARE S

1i L, 358 LBS.

tCS

-

F-IL P T EL 1987

SEATLE. WA5.NGON

98105 _USA

SHARPY-CYCLE: An Experiment in PedalPower and Screw Propulsion by Philip Thiel

What do you do if you like boatingbut do not care to cope with the whims ofthe wind, suffer the noise and smell of amotor, or fuss with oars or paddles? Usepedal power, of course!

Then you may sit comfortably facingforward, use your powerful leg musclesto spin an efficient propeller, and haveyour hands free for things more interest-ing than rowing or paddling.

The Sharpy-Cycle is one of a series ofboats exploring these possibilities. Thisexperimental model is a narrow versionof the traditional "sharpy" hull form andis lightly and cheaply built of exterior ply-wood and cedar, with fiberglas-coveredstyrofoam sponsons on the sides foradded stability. A tunnel and well arebuilt into the hull so that the propellerand shaft may be retracted for ease inbeaching and trailering. The drive systemuses stock bevel gears, pillow blocks,shaft seal and universal coupling to turnan aluminum propeller. The outboardswing-up rudder is controlled by a yokewith lines carried forward to theoperating position.

18 Human Power 7/2

After further testing this prototype"demonstrator" will be available at areasonable price.

Philip Thiel4720 7th Avenue NESeattle, WA 98105USA

Reviews(continued from page 17)

to a Draisienne brought to them for repairin 1861, when Ernest was 19 (althoughone version puts the date at 1855, whenErnest would have been 13). Ernest laterinvented and built a steam tractor. Of hisother sons, Edmond was the sales genius,Henry the promoter and manager, andFrancisque was another fine engineer andteacher. But the book also taught memuch about France of those days. Forinstance, it seems that engineers andtechnicians were forced to relocatefrequently as the economy changed andbusinesses sprang up and went under,just as today. Derek Roberts' footnotes are

invaluable. He has a double mission inlife: to record the history of the bicycleand to expunge the many myths that arerepeated endlessly in most supposed"histories." What you read here is eithertrue or questioned. There is scope forfurther work. Meanwhile, you willundoubtedly learn much from thisunpretentious but valuable book.

-Dave Wilson

AUTERNATE ENERGY TRANSPORTATION

This typewritten newsletter thatshould, presumably, be called "Alterna-tive-Energy Transportation", unless it isdesigned to complement one of thoseschemes in which motorists are allowedto use their cars every other day, is pub-lished monthly by Campbell Publishingin New York, NY. It is subtitled "Thenewsletter of technology in motion.Incorporating chopper noise." I cannothelp you decipher this. But once beyondthe title and subtitle you can find interest-ing pieces about HPVs, inter alia. It's truethat Daedalus, for instance, is referred toas a "flying moped," which seems to indi-cate further confusion by the headlinewriter. The Sunraycer and the Tour de Solare covered extensively and an IIPV Newscomment on the inclusion of hybridvehicles in our fold is quoted well.

-Dave Wilson

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HUMAN POEINDEX 1977-1988

This is a first cut at an index ofall the major articles and many of thetopics in all the 22 issues of HUMAN POWERproduced up to August 1988. The fournumbers after each entry refer to thevolume/no/year/page. The first issue wasvol.1 no. 1 Winter 1977/8 -I have used theyear in which the winter started in allcases. The next five issues have novolume nor number, and I've designatedthem as volume 1, nos. 2-6. A furthercomplication is that no. 2 was "Winter 79"but came out before no. 3, "Summer 79" -so for conformity I've re-designated no.2as "Winter 78". Likewise no. 5, "Winter81", which came out before no. 6, "Fall81", I have redesignated 1/5/80. There isonly one issue for vol. 4, and that is no.4. After that the numbering system is, Ihope, logical. To keep entries to oneline I've put in the author's name only ifthere is room. Only the number of thefirst page of a multipage article isgiven.

Paul Van Valkenburgh edited the firstfive issues, with Dick Hargrave as co-editor for layout and art work. DickHargrave was editor-in-chief of issues 6-8, with Tom Milkie as technical editor in6 & 7, and Dave Swertsen, Stuart Hustonand Chuck Champlin as co-editors in issues6, 7, & 8 respectively. I took over aseditor with the ninth issue, 3/1/84, withhelp from many dedicated people. MikeEliasohn edited all or most of 4/4/85 and6/4/87, the HPV source directories.

Let me have suggestions for improvingthe next publication of the index.

Dave Wilson

Abbott $2500 55-mph prize 1/1/77/2Abbott Prize - reflections 1/3/79/1Aerodynamic bicycle fairing 6/2/87/6Aero drag, std & recmbnt bicycles 3/4/85/3Aeroshell fairing results 1/4/80/7Aeroshell, Team 1/1/77/6Airship White Dwarf 3/3/85/1Angular momentum and stability 6/3/87/4Arm-leg cranking systems 6/3/87/8Arm-powered machines 1/2//78/2Arms race - new world record 3/1/84/8Automatic transmission, Reswick 5/4/86/16Auxiliary HP in sailboat race 3/2/84/13

Backward vs forward pedalling 6/3/87/1Backward pedalling - comments 7/1/88/8Baidarka, review 7/1/80/11Bicycle research - symposium 5/1/85/2Bioenergetics, arm-leg cranking 6/3/87/8Bionic Bat - Lynn Tobias 3/1/84/3Blimps and HP flight - Allen 3/3/85/4Bluebell's victory 2/2/83/6

British speed championshipsBritish speed-record attemptBrummer Tim - wind-tunnel testsBuilder s workshop, HPVBuilders' workshop, second,Building of HPVs - Terry HrenoBuilding BPVs - Mike EliasohnBurrows report from Britain

Cafe Racer, European HPVCarson Speed Challenge - ChamplirClarke, Arthur C.College courses in HPVsCommuting HPV, design criteriaComposites and advanced matls.Composites, cont.Computing across America - rev.Covering spoked wheels - AglerCyclecars in Sussex - Desmond

DaedalusDaedalusDaedalusDaedalus

triumphs!projectHPA rollout- photos and diagram

Danta, Randy, HPB designDatsun-Compton Grand PrixDesign considerations for HPVsDeveloping countries HPDirectors, Board of, 1977Dorycycle - Philip ThielDrag due to internal flowDragonfly II - Steve BallDutch HPV competitionDynamic stability of bicycles

Early HP blimps !Easy Racer history - MartinEasy Racer wins Du Pont PrizeEighth IHPSC report - ChamplinElectric vehiclesEvolution of new species

Fairing - Breeze-Cheater, devt.Fifth IHPSC - records & reportsFigure-eight drive - PatroniFlying Fish breaks recordFlying Fish hydrofoil - BrooksFoil propulsion at sea - JakobsenFoil-propelled kayak - GongwerFoiled Again - David Owers HPBFork angle - Mike EliasohnFree-blown canopies - Tom MilkieFriction damping as shimmy cure

Goals, rules and innovationGossamer AlbatrossGossamer Condor

1/5/80/61/6/81/101/4/80/73/4/85/15/1/85/73/4/85/54/4/85/85/1/85/6

6/2/87/72/2/83/93/3/87/191/3/79/77/1/88/11/6/81/42/1/82/87/1/88/114/4/85/42/1/82/6

7/1/88/23/1/85/1 06/3/87/1/1 /88/191/1/77/81/6/81/144/4/85/13/3/85/181/1/77/113/2/84/41/4/80/11/4/80/23/1/84/103/1/87/15

3/4/86/132/2/83/75/2/86/62/2/83/11/6/81/25/3/86/10

7/1/88/41/3/79/1

5/4/86/205/3/86/13/2/84/15/3/86/75/3/86/6

3/1/85/1/85/164/4/85/32/2/83/127/1/88/6

6/2/87/11/2//78/21/1/77/4

Hale tricycles (letter) 5/4/86/3Helfrich, Gary, master builder 3/3/85/9Helicopter Sikorsky competition 5/2/86/16Helicopter HPA update - Tobias 5/4/86/2Helicopters - Japanese work 6/1/87/3History of rowing 3/2/84/2History, IHPVA 1/1/77/10Homeless HPVs - Dennis Dollens 7/1/88/10HP floats - Alex Brooks 2/2/83/13HP foot in the door - Peter Ernst 6/2/87/4HP in developing countries 3/3/85/18

7/2 Human Power 19

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HP seacraft: Bill Watson 1/1/77/9HPA Light Eagle test flights 5/4/86/1HPA optimization - Schoberl 6/1/87/4HPA, inflatable Phoenix 3/4/85/17HPB design: Randy Danta 1/1/77/8HPB regatta - IHPVA first 3/1/84/7HPBs - comparative speeds 5/1/85/2HPBs - report on Vancouver 5/3/86/1HPBs - "Getting wet" 1/3/79/6HPV builder's workshop 3/4/85/1Human factors of long HPA flights 5/4/86/8Hybrid vehicles and HP - Schmidt 5/2/86/4Hydro Challenge (HPBs) 2/1/82/2Hydrofoil, HP, development 3/3/85/11Hydrofoil breaks 2000-m record 5/3/86/1

Icarus, The Boat that Flies 7/1/88/18IHPSC, 7th, photos & comments 1/6/81/6IHPSC, 8th, plans 2/1/82/2IHPSC highlights 1980, (photos) 1/5/80/4IHPSC: British view 1/6/81/1IHPVA history 1/1/77/10IHPVA first boat regatta 3/1/84/7IIHPVA around the world 1/2//78/7Indy photos (1984) 3/1/84/11Innovators challenge bike racers 1/3/79/7IPSOB 1/6/81/3

Japanese IHPVA competition 1/2/78/7Joyrider pedalling mechanism 3/4/85/14

Kremer prize claimed by MIT 3/1/84/1Kremer World Speed competition 3/1/84/3

Laminar-flow underwater vehicles 2/2/83/16Leitra tricycle - Rasmussen 5/1/85/14Life with an HPV builder 2/2/83/14Lightning X-2 development 3/1/84/21Linear pedalling 1/4/80/3

MacCready, Paul: goals and rules 6/2/87/1MacCready, Paul: Gossamer Condor 1/1/77/4Machine technology 1/2//78/4Madeline - pedalled sidewheeler 3/2/84/10Major Taylor - champion 6/2/87/20Mallard HPB, sea test 5/4/86/14Material selection - Bartter 4/4/85/4[le,,,ber's forum (letters &c) 2/1/82/3Michelob Light Eagle test flights 5/4/86/1MIT Monarch B: Kremer winner 3/3/85/21Monarch wins third Kremer prize 3/1/84/1Musculair 2 HPA 5/1/85/11Musculair 1 & 2 HPAs - Schoberl 5/2/86/1

Oar and rigger experiments 3/3/85/3Officers, IHPVA, 1977 1/1/77/11Oh for the wings - Clarke 6/3/87/19Olympics bicycle-design project 2/1/82/11Olympics project update - Kyle 2/2/83/1Oscillating-foil propulsion 5/4/86/7Overseas HPV competitions 3/1/84/10Oxygen cost: recumbent vs convnl 6/3/87/7Oxygen cost, pedalling - comments 7/1/88/9

Partially faired HPVs - HrenoPaul Van ValkenburghPedal height and crosswindsPhoenix inflatable HPAPhotograph album of HPVsPractical HPVs at last - Abbott

3/1/84/151 /4/80/75/2/86/3

3/4/85/171/1/77/122/2/83/8

Practical HPV competitionPressodyne II - Alec BrooksPrize donors - salute toPropeller for HPBPropellers for HPVs - LarrabeePublic-relations reportPublicity on HPVs

Ready About, reviewRecords '77Recumbents on dirt roadsRiblets for turbulent-drag redn.Rickshaw for BangladeshRickshaws in Bangladesh- WillkieRickshaws in Bangladesh, pt IIRightmyer's monocoque tripleRoad race, IHPSC '78Rolling drag - three vs twoRose, Sid, of CapetownRowing - theoretical studyRowing machine, Flexifit Ltd.

S.Africa HPV racing (letter)Safety researchScientific Symposium - secondScientific symposium, firstScientific Symp., 1st, reviewSea Saber and other HPBs - KnappShimmy cured by friction dampingSidewheeler HPB - Phillip BolgerSolar: human power? Peter ErnstSource guide, builders', secondSource directory, firstSource-guide updateSpeed-sailing week - reportSpoked-wheel responseStability, dynamic, bicycleStability of bicycles & momentumSteering geometry noteSubmarine, HP competitionSubmarine, HP, O'Neil dry HPSSubmerged-buoyancy HPB - SchmidtSwinging-arc pedalling

Tandem recumbent - Kurt WoldTen-speed fairingsTherrio, Ralph: AeroshellTraction on ice, how to getTrailer, construction of FlunderTransmission, automatic, ReswickTravelling with the VectorTricycle steering geometryTricycles, long and short WBTriflex speed vehicle - GentesTube-frame recumbent suggestedTwenty-knot HPB - Alec BrooksTwo wheels vs three wheels

Van Valkenburgh, story of recordVector record run on freewayVectorl World's fastest HPVVentilation of faired HPVs

Water Strider HPBs - Richard OttWaterbug HPBWatson, Bill: HP seacraftWhite Lightning - wind-tunnelWhite Dwarf HP AirshipWho needs a wind tunnel? - WhiteWinter tricycle - Fred Willkie

20 Human Power 7/2

2/1/82/21/4/80/33/1/84/143/2/87/103/2/84/101/3/79/61/1/77/7

5/4/86/141/1/77/165/2/86/135/2/86/34/85/27

5/3/86/195/4/86/51/5/80/31/1/77/9

5/1 /85/1 21/2//78/83/2/84/3

7/1/88/1 5

2/2/83/23/1/84/233/1 /84/181/6/81/22/1/82/53/2/84/127/1 /88/63/2/84/105/1/85/16/4/87/14/4/85/25/3/86/137/1/88/3

5/2/86/12/1 /87/1 56/3/87/4

5/1/85/136/3/87/3

7/1/88/173/3/85/63/4/85/14

6/3/87/33/1/84/231/1/77/6

5/4/86/1 36/1/87/205/4/86/152/2/83/144/4/85/54/4/85/31/4/80/44/4/85/76/1/87/14/4/85/1

1/1/77/61/5/80/11/3/79/46/2/87/5

3/2/84/1 53/4/85/101/1/77/91/4/80/63/3/85/11/5/80/7

3/4/85/11

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