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Clutches A clutch is a mechanical device that provides for

the transmission of power (and therefore usually motion) from one component (the driving member) to another (the driven member) when engaged, but can be disengaged.

In the simplest application, clutches connect and disconnect two rotating shafts (drive shafts or line shafts). In these devices, one shaft is typically attached to a motor or other power unit (the driving member) while the other shaft (the driven member) provides output power for work. While typically the motions involved are rotary, linear clutches are also possible.

In a torque-controlled drill, for instance, one shaft is driven by a motor and the other drives a drill chuck. The clutch connects the two shafts so that they may be locked together and spin at the same speed (engaged), locked together but spinning at different speeds (slipping), or unlocked and spinning at different speeds (disengaged).

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Location of Clutches Rear wheel drive

Front engine Rear engine Mid engine

Front wheel drive

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Construction Of Clutches

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Coil spring pressure plate (cover and pressure plate)

44-3 Construction of the Clutch

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Splines to input shaftOf transmission

Clutch Disk orFriction Disk

Pilot Bushing or bearing

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Construction of the Clutch

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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.

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Bolted to Crank

(friction disk) splined to transmissionInput shaft

(throw-out bearingT/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

Pressure Plate

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PivotsT/O bearing

Moves pressurePlate right

Releases friction diskfrom flywheel

Clutch terms

Clutch disengagedClutch pedal is in or down

Clutch engagedClutch pedal is out or up

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What would it mean if someone said the clutch pedalIs engaged?Make sure you know if you are talking about the clutch or the clutch pedal !!!

Throw out Bearing (release bearing)

Slides on transmission input shaft bearing retainer

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Clutches

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READ ON

Slipping clutch

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Clutch Linkage

Can be very complicatedHave the right amount of

movement and direction without too much pedal pressure

WearMotor mountsSpring to pull T/O bearing

awayHas to be lubricated

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Clutch fork

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T/O bearinghooks here

Fulcrum point

Hydraulic clutch

Uses master cylinder and slave cylinder Uses brake fluid Must be bleed

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Hydraulic clutch

No complicated linkage

Can easily control mechanical advantage with piston sizes

Self lubricating No motor mount

problems

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Service just like you would hydraulicbrakes

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Slave cylinder

Some are adjustablefor free-play and

some not

Cable clutch

No complicated linkage

Flexibility No motor mount

problems

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Friction disks

Often made of asbestos

Must be put in only one wayUsually markedClutch won’t

release if wrong

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Friction disks Cushion springs

Waved metal between clutch half'sDampen clutch engagement

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Friction disks Torsional springs

Can be spring or rubberDampen power impulses from crankshaft

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Torsional Springs

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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

Clutch disks

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Friction material isn’t very thick.Minimum thickness around .012”

Types of Clutches (pressure plates)

Coil spring9 spring12 spring

3 fingers for T/O bearing to push on

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Diaphragm-Spring Clutches

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Diaphragm-Spring Clutches

Centrifugal Clutch The faster the RPM, the harder the

clutch disk is squeezed

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Multi-plate Clutch

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Conical Clutch

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Clutch Safety Switch

Prevents from cranking with clutch engaged

Some standard transmissions won’t let you take the key out and lock the steering column with out the transmission in reversePrevents steering lock while moving forward

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Checking pressure plate for warpage

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Clutch Disk Replacement

Very wise to:Have flywheel surfaced (even with no run-

out or hot spots)Replace pilot bushing or bearingReplace T/O bearingReplace pressure plate (cover, plate

springs)

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Clutch Disk Replacement

Very wise to inspect & replace as necessary:Clutch fork & pivotInput shaft bearing retainer on transmission

(where T/O bearing slides)Linkage, cable or hydraulic componentsMotor mountsFlywheel ring gear

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Universal clutch alignment tool Select end that fits tight in pilot bushing

or bearing

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Universal clutch alignment tool

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Universal clutch alignment tool

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Clutch Alignment tools (pilot shaft)

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