1. Clutches

2. Definition
A clutch is a mechanism for connecting and disconnecting an engine and the transmission system in a vehicle, or the working parts of any machine. It allows a temporary separation of drive between drive source and driven mechanisms. When engaged this will allow for a smooth take up of drive as the clutch is gradually engaged.

3. Clutch Action Clutch action can be demonstrated by two discs
Drive Disc
Input Shaft to Transmission
Drive disc attached to engine
Driven disc attached to transmission input shaft
Engine
Driven Disc
Driven disc disconnected, no drive
Driven disc in contact with drive disc, drive applied
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5. Clutch System Parts Clutch system consists of: Flywheel Clutch Plate
Clutch Housing
Clutch Plate
Flywheel
Pressure Plate Assembly
Release Bearing
Release Bearing
Clutch Fork
Clutch Plate
Clutch housing protects clutch components from outside elements
Pressure Plate Assembly
Clutch Fork
Clutch Housing
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6. Clutch System Parts - Clutch Plate - 1
Friction Material
Rivets
Located between flywheel and pressure plate
Splined Hub
Splines mesh with input shaft
Friction Ring
Frictional material riveted to cushion springs on either side of friction ring
Cushion Springs
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7. Clutch System Parts - Clutch Plate - 2
Cushioning springs cushion force as pressure plate pushes clutch plate onto flywheel
Torsional Spring
Cushion Springs
Torsional springs soften load applied to clutch plate as it begins to turn
Cushion Springs
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8. Clutch Operating Mechanisms - Hydraulic
Master Cylinder
Pipe connected between foot pedal and clutch fork
Two cylinders: master cylinder and slave cylinder
Slave Cylinder
Pipe
As foot pedal depressed, master cylinder builds pressure in system, slave cylinder activated
As foot pedal released, springs return system to rest position
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10. Clutch Types & Applications
Single Plate clutch is used in almost all motor vehicles where manual transmission takes place
Cone clutch was used in some automobiles in the past, but now is restricted to racing / rally car & power boats
Centrifugal clutch is used on a petrol powered lawn mower-as the lawn mower is revved at a higher speed, the centrifugal force spreads the clutch shoes apart so the clutch mechanism engages
Multi Plate clutches are used in extreme car racing and in automatic gearboxes.

11. Flat Plate Clutch

12. Cone clutch α = semi-apex angle of the cone w T = μWrm cosecα
Only one pair of driving surfaces is possible, n =1 α w
Driving shaft
Driven shaft
Friction lining
The maximum torque transmitted =
T = μWrm cosecα

13. Centrifugal clutch F=mrω2 ω Driven shaft Driving shaft Friction lining
Total friction torque , T = nµR(F-P)
F=mrω2 ω P R

14. Multi plate clutches
In a multi plate clutch, the torque is transmitted by friction between several pairs of co-axial annular driving faces maintained in contact by an axial thrust.
Both sides of each plate are lined with friction material, so that a single-plate clutch has two pairs of driving faces in contact.
The advantages of using these types of clutch are due to the frictional surface area used, a lesser diameter clutch plate can be used thus less space is used.

15. Multi plate clutch driver driven Pressure plates 1 2 3 4 6 5
Friction plates 2 1 4 3 6 5