What is the purpose of Fingers in pressure plates?
The pressure plate pushes the clutch disc, sometimes called the
clutch plate, against the constantly spinning engine flywheel. The
clutch disc, therefore, is either stationary or rotating at the
same speed as the flywheel. Friction material, similar to that
found on brake pads and brake drums, causes the clutch disc to spin
at the same speed as the engine flywheel. It is this friction
between clutch disc and flywheel that allows the engine torque to
drive the wheels.
Pressure plates are, as the name implies, round, metallic
devices containing springs and fingers, or levers, and controlled
by the release fork connected to the shifter. All of the clutch
components are enclosed in the bell housing of the transmission,
between the rear of the engine and the front of the gearbox. The
purpose of pressure plate fingers are as follows: When the driver
steps on the clutch pedal, a number of springs in the pressure
plate are compressed by multiple - most often three - fingers. This
compression of the spring(s) pulls the pressure plate and the
clutch disc away from the flywheel and thus prevents the clutch
disc from rotating. When the clutch disc is stationary, the driver
can shift into the proper gear and release the clutch pedal. When
the pedal is let up, the fingers in the pressure plate release
their grip and the spring(s) expand to push the pressure plate into
the clutch disc, thereby engaging the flywheel. This release
process is often called the "clamp load".