Introducing Clutches & Gears

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2Purpose of the Clutch Allows engine to be disengaged from transmission forshifting gears and coming to a stop Allows smooth engagement of engine to transmission

• Easy to operate.• As small as possible.• Dynamically balanced.• Damp the vibrations and noise.• Dissipate maximum amount of heat.• Engage gradually to avoid sudden jerks.• Transmit maximum torque of the engine.

Requirement of Clutch

3Clutches

Rear wheel drive Front engine Rear engine Mid engine

Front wheel drive

Coil spring pressure plate (cover and pressure plate)

Construction of the Clutch

Location of the Clutch

4Clutches

Flywheel boltsto crankshaft

Pressure plate & coverbolt to flywheel

If there is a chance you will be reusingpressure plate, make alignment marksto flywheel to maintain proper balanceBEFORE removal

When unbolting pressure plate from theflywheel, remove bolts evenly as not tobend the cover. REMEMBER, this is under high spring pressure.

5Flywheels Add weight to crank for non-power strokes Has ring-gear for cranking engine (usually

replaceable)

6Clutches

Bolted to Crank

(friction disk) splined to transmissionInput shaft

throw-out bearing(T/O bearing) allowsto push on rotatingclutch fingers

Bolted to flywheel - Applies the spring force to clamp thefriction disk to the flywheel

(clutch fork) pushesT/O bearing to releaserotating clutch

Pilot bushing or bearing in centerof flywheel or crankshaft, supportsthe end of input shaft

7Types of Clutches (pressure plates)

Coil spring 9 spring 12 spring

3 fingers for T/O bearing to push on

8Torsional Springs

Has pins to limit amount of twist.Springs try to keep it centered between pins.

Springs sometimes get weak and start rattling or fall out

9Diaphragm-Spring Clutches

GEARSGears Purpose

Normally mounted on shaftTransmits rotating motion from one parallel shaft

to anotherTransmit rotating motion

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Types of Gears 11

Helical Gear Are quieter than spur

gears Two teeth at a time

contact Has a tendency to move

shaft for and aft Are left and right handed Opposites on parallel

shafts

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Drives a spur gear Provides maximum

tooth contact Used in recirculating

ball steering boxes Speedometer cable

drive mechanisms

Worm Gear 13

Bevel Gears

Change the direction of rotation

Spider gears are straight cut bevel gears

Transfer motion between two shafts at an angle to each other

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Gear Ratios Gear Ratio can be found by dividing number of teeth on

driven gear by the number of teeth on the driving gear. Ex: 75 driven teeth : 45 drive teeth = 1.66 gear ratio

Can multiply torque and speed Can reduce torque and speed Same size and number of teeth = no change in

output Equal size gears create equal output Small drive gear to larger driven gear = driven gear

speed decreases Larger drive gear to smaller driven gear = driven

gear speed increases

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