Friction value, spring tension, friction area -> transferable torque
The dry-clutch has mostly, only one clutch plate, the coating of which is laid out for dry friction and a higher friction value. The transferable torque depends not only on this lining, but also on the size and amount of friction areas and the pressure force.
Flywheel - clutch plate - pressure ring
The flywheel (1) and the pressure ring (3) are solidly connected to the crankshaft (7) and transfer the torque through the friction surfaces of the clutch plate (2) to the transmission drive shaft (6). The clutch plate is tightly clamped between the flywheel (1) and the pressure ring (3).The necessary pressure force is provided by membrane springs (4). The clutch cover (5), the pressure ring (3) and the membrane spring are collectively known as the clutch system.
A clutch can be operated either by pulling or pushing.
One distinguishes between the pressed version, (see left figure) mainly used for motor cars, and the pulled version, (see right figure) which is mainly found inutility vehicles. In a direct comparison,the latter is slightly lighter and has a more favourable operation/pressure force ratio.
The highest wear and tear takes place at about the middle of the pedal travel distance.
The highest amount of wear on the clutch plate occurs at the pressure point when engaging the clutch. If the pressure plate is movedaway from the flywheel, friction with the clutch plate no longer exists and the connection is broken. This movement can occur either through a cable, linkage rods or it can be hydraulically operated. Instead of beingoperatedby the driver, an electric or pneumatic servo-motor with a control device is also possible.
Double plate clutch -> double the amount of transferable torque.
In the case of the double plate clutch, an additional pressure plate, (intermediate plate) which is solidly fixed to the flywheel, and a second clutch plate on thegearing of the gearbox shaft areadded. Through the two-fold friction area, twice the amount of torque can be transferred.
A clutch can slip, refuse to disengage and pluck.
The most common damage found in the clutch, is too little friction (slipping) between the clutch- and pressure plate or the the flywheel. This can be caused by oil leakage, lining wear, worn outsprings or to little clutch-play. One notices it, e.g., when pulling off, the engine revs higher at that speed than it would do normally. If the clutch only partially disengages, or not at all, the reason could be that the clutch plate is skew, the lining is sticky, the clutch plate is solidly rusted onto the gearing, or there is too much clutch play. If a gearcannot be engaged at all, the gearbox willinform you by making unusual and unpleasant grating noises. More seldom is a plucking clutch, which is caused by eneven linings or friction. In this case, evenexperienced drivers can be made tolook like beginners. This means, at least a new clutch plate is due. 10/10
Wear and tear -> too little clutch play (without readjustment!).