Module 8: Special Drives - Jones & Bartlett Learningd2jw81rkebrcvk.cloudfront.net/assetscdx/diesel/resource/pdf/rfr/... · Module 8: Special Drives ... Arc is the contact or wrap

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CDX Diesel Drive Trains

Module 8: Special Drives

� Alignment is the adjusting or positioning of parts to bring into line.

� Arc is the contact or wrap between belt and pulley. � Belt creep is the slight stretching of the belt as it

runs over the pulley.Note: The words “sheave” and “pulley” mean the same thing.

� Belt slip is the slight loss of speed between the drive and driven pulleys as a result of insufficient grip between belt and pulleys.

� Chain pitch is the distance from the center of one pin to the center of the next pin.

� Detachable-link chain is a series of formed links, either open or closed, that can be detached and are either malleable cast iron or pressed steel.

Note: Detachable-link chains are also called plain chains.

� Displacement is the quantity of fluid a pump can move during each revolution.

� Flat belt is a belt of flat construction used where pulleys are far apart and high power is needed for a separate machine such as in old threshers or sawmills.

� FPM is an abbreviation for “feet per minute.” � Gear drive is a type of drive in which a system of gear

arrangement is used to transmit power.Note: When two gears are in mesh, all slippage is

gone; for this reason, gears are widely used for high power applications.

� Hydrostatic drive is a drive using fluid under pressure to transmit engine power to the driven unit.

� ID is used as an abbreviation for “inside diameter.” � Misalignment occurs is when bearings are not on the

same center line with good functional or working limits.

� OD is an abbreviation for “outside diameter.” � Reciprocating drives are drives that change a rotary

motion to a linear motion as with mowing cutter bars. � Roller chain is made up of alternate roller links and

pin links with pins and free rolling bushings. � Silent chain is a series of flat metal links, with a

tooth shape at each end, connected by pins to form a flexible continuous chain.

� Sprocket pitch is the distance between one point on a sprocket tooth and the corresponding point on the next tooth.

� Tension is an effort that elongates or stretches a material.

� Variable speed drive has the ability to change the speed of a driven component by changing revolutions per minute (RPMs), sheave size, or gear size.

� V-belt is a belt of V construction used for driving light loads between short-range pulleys; the load is carried on the sides of the belt.

ÂTeRMS AnD DeFInITIOnS

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ÂDeTACHABLe-LInk CHAInS

ÂROLLeR CHAInS

ÂSILenT CHAInS

ÂCHARACTeRISTICS OF DeTACHABLe-LInk CHAInS

ÂCHARACTeRISTICS OF STAnDARD PITCH ROLLeR CHAInS

ÂCHARACTeRISTICS OF DOuBLe PITCH ROLLeR CHAInS

ÂCHARACTeRISTICS OF SILenT CHAInS

ÂPRInCIPLeS OF CHAIn DRIVeS

ÂALIGnMenT OF SPROCkeT SHAFTS AnD SPROCkeTS

ÂADJuSTMenT OF CHAIn TenSIOn

ÂMeTHODS OF ADJuSTInG CHAIn TenSIOn

ÂPARTS OF A CHAIn SPROCkeT

ÂWORn CHAInS AnD SPROCkeTS

ÂReASOnS FOR LuBRICATIOn OF CHAInS

ÂMeTHODS OF LuBRICATInG CHAInS

ÂRePAIR OF CHAIn DRIVeS

ÂCLeAnInG CHAInS

ÂTyPeS OF BeLTS

Â FACTORS GOVeRnInG THe ABILITy OF BeLTS TO TRAnSMIT POWeR

ÂBeLT DRIVe ARRAnGeMenTS

ÂBeLT SeCTIOnS uSeD On COMBIneS

ÂVARIABLe SPeeD DRIVeS

ÂBeLT TenSIOn

ÂBeLT CARe AnD MAInTenAnCe

ÂMAInTenAnCe OF PuLLeyS OR SHeAVeS

ÂTyPeS OF GeAR DRIVeS

ÂMeTHODS OF LuBRICATInG GeARS

ÂGeAR BACkLASH

ÂTyPeS OF ReCIPROCATInG DRIVeS AnD THeIR CHARACTeRISTICS

ÂMAInTenAnCe OF ReCIPROCATInG DRIVeS

ÂHyDROSTATIC DRIVeS

ÂReVeRSInG HyDROSTATIC DRIVeS

ÂMAInTenAnCe OF HyDROSTATIC DRIVeS

ÂTeSTInG HyDROSTATIC DRIVeS

Â FunCTIOnS OF A SAFeTy ReLeASe MeCHAnISM

ÂTyPeS OF SAFeTy ReLeASe MeCHAnISMS AnD THeIR DeSCRIPTIOnS

ÂMAInTenAnCe OF SAFeTy MeCHAnISMS

Terms and Definitionsready for review


CDX Diesel Drive Trains Module 8: Special Drives

� Detachable-link chain. � Roller chain.

� Silent chain.

� Series of formed links (closed or open). � Detachable links. � Larger plain chains are of pintle construction.

� Low speed use (conveyors or drags). � Open plain chains used in light loads. � Closed pintle chains used in heavier loads.

� used at speeds up to 500 RPM. � Low in cost. � Ideal for conveyor or elevator work. � Provide better wear under dirty conditions.

� Malleable cast iron chain more resistant to corrosion than steel (pintle).

� Pressed steel has lower initial cost.

Types of Chain Drivesready for review

Detachable-Link Chainsready for review

Roller Chainsready for review

� May be installed in multiple strands for heavier loads. � Have less vibration than plain chains. � Good for low to medium speed heavy loads with

sprockets far apart.

� Made up of pin bushing and roller for less wear. � Two types of roller chains, single pitch and double

pitch.

Silent Chainsready for review

� Sprockets are similar to gears in appearance. � Quieter operation and less vibration. � Can operate at higher speeds.

� Some have links with teeth on both sides so that over-and-under drives can be used (serpentine drives).

� used as timing chains.

Characteristics of Detachable-Link Chainsready for review

Characteristics of Standard Pitch Roller Chainsready for review

� Satisfactory at speeds of 100 FPM to 4,500 FPM depending on pitch.

� As speed increases the pitch must be decreased. � May be 98% to 99% efficient under ideal conditions.

� Oil bath lubrication desired for high speed drives. � Sprockets may be driven from either side the of the

roller chain.

Characteristics of Double Pitch Roller Chainsready for review

� Similar to standard pitch roller chains, except is twice the pitch of standard chain.

� Satisfactory for small sprocket speeds of up to 600 RPM.



� More satisfactory at higher speeds than roller chains. � Have practically no sliding action.

� Most commonly used in final drives of tractors and transfer cases for four wheel drive vehicles.

Characteristics of Silent Chainsready for review

Principles of Chain Drivesready for review

� Chain drives consist of one or more sprockets and an endless chain.

� The links of the chain mesh with the teeth of the sprocket and maintain constant speed ratio between the drive and driven sprockets.

� Sprockets on the same side of a chain turn in the same direction.

� Sprockets on the opposite side of the chain turn in opposite direction.

� Sprockets should always be no smaller than ten teeth to prevent excessive wear.

� If the chain has an even number of pitches, the sprockets have to have an odd number or teeth or vice versa.

Note: If pitches and teeth are both odd or even, it will cause uneven chain vibration.

� The smaller the sprocket, the more wear on chain and sprocket.

Note: On small sprockets, the chain bends more, causing more wear on chain, and the small sprocket turns more RPM than the larger sprocket, causing more wear on smaller sprockets.

Alignment of Sprocket Shafts and Sprocketsready for review

� Level each shaft with machinist’s level or protractor. � Align all shafts parallel to each other by making sure

the distance between the shafts is equal on both sides of the sprockets.

� Align sprockets with straight edge on the finished surfaces on the sides of the sprockets.

Adjustment of Chain Tensionready for review

� Horizontal and inclined drives.• The chain sag should be about ¼ inch per foot

between shaft centers.• All slack should be on one side.

� Vertical drives and shock loading or reversible rotation drives’ chains should be almost taut.

Methods of Adjusting Chain Tensionready for review

� Moveable sprocket shafts. � Adjustable idler sprockets.

� Adjustable shoe.

Parts of a Chain Sprocketready for review

� Tooth height. � Tooth thickness. � Tooth width. � Point width. � Tooth face. � Base circle.

� Pitch circle. � Outside circle.

Note: Base circle, pitch circle, and outside circle are imaginary terms used to define movement and are not physically parts of a chain sprocket.



� Adjuster has reached end of travel. � Chain begins to ride on the tips of the sprocket teeth.

Note: If adjuster has reached the end of its travel, and chain still fits sprocket, remove chain links and readjust to proper tension.

� Manual lubrication.• Applied with brush on chain.• Applied with spout can.

Note: Lubricate every 8 hours or when oil starts to discolor between joints; manufacturer’s specifications for lubrication should be followed carefully.Caution: never manually lubricate a chain that is moving.

� Drip lubrication.• Oil drops are directed between the link plates.• Oiling should be sufficient to prevent discoloration

of oil between joints. � Oil bath lubrication.

• Lower strand of chain runs through a sump of oil.• Oil level should reach pitch line of chain at its

lowest operating level.

� Disc lubrication.• Chain runs above oil level in sump.• Disc rotates and picks up oil and deposits it onto

the chain by means of a trough or collector. � Oil stream lubrication.

• Lubrication is supplied by a pump onto chain through a nozzle.

• excess returns back to pump.• Properly lubricated chains will not show a

brownish color at joints, and connecting link pins will be brightly polished.

Worn Chains and Sprocketsready for review

Reasons for Lubrication of Chainsready for review

� Reduces wear. � Protects against corrosion.

� Prevents galling. � Prevents seizing of pins and bushings.

Methods of Lubricating Chainsready for review

Repair of Chain Drivesready for review

� Grind off heads of link pins or remove keys. � Drive out the two pins of the link evenly.

Note: A chain-breaking tool is an efficient method of removing links.

� Reverse sprockets, if design permits.Note: Reversing sprockets can increase sprocket life.

� Do not install new chain on worn sprockets. � Do not add new chain links to worn chain.

Cleaning Chainsready for review

� Wash chain in cleaning solvent. � Drain and dry chain.

� Soak chain in oil. � Hang chain to let excess oil drain off.



� Flat belt. � V-belt. � Round belt.

� Polygrooved or ribbed belt. � Cogged belt.

� Open. � Turned. � Crossed.

� Serpentine. � Mule.

Types of Beltsready for review

Factors Governing the Ability of Belts to Transmit Powerready for review

� Tension of belt. � Friction of belt to pulley.

Note: Type of material belt and pulley are made of help determine the amount of friction.

� Speed of belt.Note: The higher the speed, the less contact and friction between belt and pulley.

� Belt wrap on pulley.Note: The more wrap on a pulley, the more area for friction contact.

Belt Drive Arrangementsready for review

Belt sections Used on Combinesready for review

� 1⁄2 × 5⁄16

� 21⁄32 × 13⁄32

� 7⁄8 × 17⁄32

� 1 1⁄4 × 3⁄4

� 1 3⁄4 × 25⁄32

� 2 1⁄4 flat 12 ribs

Variable Speed Drivesready for review

� uses of variable speed drives.• Verify production rates.• Adjust speed of drive component. • Offer less torque with more speed on lighter loads.• Offer more torque with less speed on heavy loads.• Offer a variety of speeds for different applications.

� Causes of speed variation.• RPM: The driving component may have the

capability to speed up or slow down resulting in more or less output to the driven component.

• Sheave size: Sheave size can determine the speed of the driven component; for instance, if you increase the size of the sheave, you will slow down the driven components.

• Gear size: Gear size can determine the speed of the driven component; some gear selections can be made manually by the technician or automatically by the component at the will of the operator.



� Results of too little tension on belt.• Broken belt.• Burned spots.• excessive cover wear.• Overheating of belt and pulley.• excessive slippage.

� Results of too much tension on belt.• Belt heating.• excessive stretch.• Damage to bearings in drive and driven units.• Damage to pulleys.

� Correct tension on V-belt.• Belt should show springiness when hit with the

hand.• Belt tension gauge should be used if space

permits.• note: Belt tension should always be set according

to manufacturer’s specifications.• Belt should be readjusted after 1 hour of operation

and checked periodically.Note: Initial belt seating and stretch occurs during first 24 hours of operation.

� Worn sheave grooves can be caused by:• Dust.• Corrosion from moisture and chemicals in the air.

Note: When sheave grooves are worn 1⁄32 inches or more, the sheave should be repaired, regrooved, or replaced.

� Shiny sheave groove bottom can be caused by:• Worn belt. • Worn sheave.• Wrong sheave.• Wrong belt.

Note: Shiny sheave bottom groove is caused by belt bottoming in sheave groove.

� Wobbling sheaves can be caused by:• Bent shaft. • Bent sheave. • Worn bore in sheave. • Worn or damaged shaft bearings.

Note: A wobbling sheave should be corrected at once to prevent belt or unit damage.

Belt Tensionready for review

Belt Care and Maintenanceready for review

� Problems caused by oil and grease.• Causes belts to become soft.• Causes belts to slip.

� Problems caused by heat over 120° F.• Belts may harden. • Belts may crack.• Belts may stretch.

Note: Be sure to keep belts ventilated properly by keeping shields and screens clean.

� Matching of belts.• If one belt in a set needs to be replaced, replace all

belts in that set. • never use belts manufactured by different

companies in the same set. � A belt should seat 1⁄16 inches above or below outer

edge of sheave.

Maintenance of Pulleys or Sheavesready for review

Types of Gear Drivesready for review

� Screw gears are used in screw jacks and in machine feed.

� Bevel gears are used to change direction such as hand crank controls or in ring gear and pinion such as rear axle, right angle drives.

� Worm gears are a type of screw gear that are used in steering gears, winch drives, and in applications with high speed input and low speed output.



� Splash pan, which the gears run through. � Hand lubrication by brushing or squirting lubricant on

gears. � Automatic lubrication by drip oiler.

� Pressure lubrication by means of a pump.Note: Gear drives require many types of lubrication from simple oils to complex formulas. For type of lubricants to use, consult manufacturer’s operator’s manual.

Note: A reciprocating mechanism is not actually a drive, but is a supplement or helper for the drive.

� Crankwheel and lever.• Crankwheel has lever mounted off center.• As wheel turns one revolution, lever makes two

strokes.Note: A mower cutting bar is an example of a machine using this principle.

� Crankarm and lever drive.• Operates like a crankshaft and rod assembly in an

engine.• Has a flywheel or counterbalance to offset the

inertia of the sudden changes in direction.

• The direction of the counterbalance is always the opposite of the pitman or lever.Note: The plunger head in a hay bailer is driven by a crankarm and lever assembly.

� Cam drives.• Change rotary motion to reciprocating motion by

use of a cam and cam follower.• Cam follower always returns to the same starting

point.• Action may be simple direct motion, complicated

motion, or delayed motion.• Cam drives may use a spring load, gravity, or a

track to return them to their starting position.

Methods of Lubricating Gearsready for review

Gear Backlashready for review

� Gear backlash is the clearance or play between two gears.

� Too much gear backlash can be caused by any of the following:• Worn gears.• Improper meshing of teeth.• Worn bearings.• Improper bearing adjustment.

� excessive backlash results in severe gear teeth impact causing damage to gear teeth.

� Gear backlash is adjusted either by shims or by bearing preload.

� Gear backlash in some cases is preset at manufacture by gear and bearing arrangement.

Note: Always set gear backlash according to manufacturer’s service manual.

� not enough backlash results in binding of gears once gears heat up and expand.

Types of Reciprocating Drives and Their Characteristicsready for review

Maintenance of Reciprocating Drivesready for review

� Lubrication is the key to good operation of all mechanical drives; any moving part that contacts another part should be lubricated.

� Bearings should be kept lubricated and checked for wear or damage periodically.

� Cam tracks or cam surfaces require greasing for smooth operation and minimum wear.

� Hinged areas need lubrication. � enclosed drives should have oil level checked

periodically. � Refer to machine operator’s manual for proper

lubrication periods and type of lubricants.



� Fixed displacement pump with fixed displacement motor.• Constant input speed gives constant horsepower

and torque at the output.• Input speed varies; output horsepower and speed

will vary, but torque will remain the same.• When both pump and motor are fixed displacement

they act as a gear drive. � Variable displacement pump with fixed displacement

motor.• Pump output is variable, motor output speed is

variable, and torque output is constant for any given pressure.

• This type drive gives variable speed and constant torque.

� Fixed displacement pump with variable displacement motor.• Output speed is controlled by changing the motor

displacement. As motor displacement decreases, output speed increases, and torque decreases.

• When balanced, constant horsepower output is obtained.

� Variable displacement pump with variable displacement motor.• Output of both constant torque and constant

horsepower (torque × speed = horsepower).• Most flexible drive but also is the most difficult to

control.

� Reversing output shaft of motor can be done by shifting either the pump or motor swashplates.

� In neutral, the swashplate is vertical and no oil is pumped.

� In forward, the swashplate is tilted and oil is pumped in one direction.

� In reverse, the swashplate is tilted the opposite way and oil is pumped the opposite direction reversing the motor output.

� note: The pump drive shaft always rotates clockwise, but the motor drive shaft can rotate in either direction, depending on the direction of the oil flow from the pump.

Hydrostatic Drivesready for review

Reversing Hydrostatic Drivesready for review

Maintenance of Hydrostatic Drivesready for review

� Clean unit before removing components.• Steam clean entire area around component to be

worked on.• If steam cleaning is unavailable, use a cleaning

solvent.Note: never use paint thinner, gas, or acetone to clean the area to be worked on; they are fire hazards and could damage hoses.

• Prevent water from entering system when steam cleaning.

� Precautions to take before repairing pump or motor.• Seal all lines and fittings with plastic bags or plugs

as lines are removed.

• Have a container of clean solvent to wash parts in.• Have clean, dust-free work area.• Have a container of clean transmission fluid to

lubricate parts as they are assembled.• Have a container of clean petroleum jelly to

lubricate surfaces where needed.• Have new o-rings and gaskets.• Have new or clean oil for system.

Note: Internal service on either the pump or motor must be done under extremely clean conditions. The tolerances in these units are similar to those in diesel injection pumps, and equal care must be taken.

Testing Hydrostatic Drivesready for review

� Test charging and operating oil pressures. � Test for oil flow rate and oil temperature.

� use the proper test equipment and procedures as given in the machine technical manual.



� Relieves shock on the power source. � Protects machine doing the work.

Note: In a machine where one power source drives several work functions, and each function has a

different work load, a torque limiting factor or safety release mechanism is placed in the power line to prevent damage in case an obstruction enters the machine.

� Lubrication of safety mechanisms:• Light coat of oil on faces of clutches to prevent

sticking.• Too much oil causes slipping.• Lubricate springs.• Lubricate shafts where they come together.

� Follow machine specifications for adjustment of safety mechanisms and proper shear pins.

Functions of a Safety Release Mechanismready for review

Types of Safety Release Mechanisms and Their Descriptionsready for review

� Slip clutches.• Installed in drive line.• Works by means of friction discs and springs.• Obstruction in machine overcomes friction clutch

facings, preventing damage to machine.• Tension can be adjusted at the springs.

� Jump clutches.• Installed in drive line.• Have ratchet teeth and spring tension.• In case of overload, the spring tension is overcome

and ratchet slips, disengaging the power train.• Tension should be adjusted at the spring.

� Shear pin.• Works on stress principle.• The harder the pin, the more force it takes to

shear.• When an obstruction enters the machine, the pin

will shear, protecting the machine.• Shear pins are inexpensive.• When the pin shears, the machine is inoperative

until the pin is replaced.

Maintenance of Safety Mechanismsready for review

Documents

Module 8: Special Drives - Jones & Bartlett Learningd2jw81rkebrcvk.cloudfront.net/assetscdx/diesel/resource/pdf/rfr/... · Module 8: Special Drives ... Arc is the contact or wrap