HOW THE CLUTCH WORKS
The clutch is a device to engage and disengage power from the engine, allowing the vehicle to be stopped and started. A pressure plate or “driving member” is bolted to the engine flywheel and a clutch plate or “driven member” is located between the flywheel and the pressure plate. The clutch plate is splined to the shaft extending from the transmission to the flywheel, commonly called a clutch shaft or input shaft. When the clutch and pressure plates are locked together by friction, the clutch shaft rotates with the engine crankshaft. Power is transferred from the engine to the transmission, where it is routed through different gear ratios to obtain the best speed and power to start and keep the vehicle moving.
The flywheel is located at the rear of the engine and is bolted to the crankshaft. It helps absorb power impulses, resulting in a smoothly-idling engine and provides momentum to carry the engine through its operating cycle. The rear surface of the flywheel is machined flat and the clutch components are attached to it.
THE PRESSURE PLATE
The driving member is commonly called the pressure plate. The pressure plate consists of a heavy metal plate, coil springs or a diaphragm spring, release levers (fingers), and a cover.
THE RELEASE BEARING
The release (throw out) bearing is usually a ball bearing unit, mounted on a sleeve, and attached to the release or throwout lever. Its purpose is to apply pressure to the diaphragm spring or the release levers in the pressure plate. When the clutch pedal is depressed, the pressure of the release bearing or lever actuates the internal linkages of the pressure plate, releasing the clutch plate and interrupting the power flow. The release bearing is not in constant contact with the pressure plate. A linkage adjustment clearance should be maintained.
MECHANICAL CLUTCH ACTIVATION
The clutch pedal provides mechanical means for the driver to control the engagement and disengagement of the clutch. The pedal is connected mechanically to either a cable or rods or hydraulic master and slave system, which are directly connected to the release bearing lever.
POWER FLOW ENGAGEMENT
While the clutch pedal is depressed and the power flow interrupted, the transmission can be shifted into any gear. The clutch pedal is slowly released to gradually move the clutch plate toward the flywheels under pressure of the pressure plate springs. The friction between the clutch plate and flywheel becomes greater as the pedal is released and the engine speed increased. Once the vehicle is moving, the need for clutch slippage is lessened, and the clutch pedal can be fully released.
Coordination between the clutch pedal and accelerator is important to avoid engine stalling, shock to the driveline components and excessive clutch slippage and overheating unless it is hydraulic.