Barir's World

How It Works: Clutch Play

To get the clutch moving, the clutch pedal is connected to a sheathed cable or a hydraulic master cylinder and slave cylinder. The cable system works much like a heavy-duty version of the brake-caliper cable that can be found on a 10-speed bicycle-depressing the pedal pulls on the cable to release the clutch. With the hydraulic system, pressing on the clutch pedal moves a piston in the master cylinder, which displaces fluid, causing the piston in the slave cylinder to move. This, in turn, operates the clutch. Some older cars and trucks use a simple mechanical bellcrank linkage instead of a cable or slave cylinder, but the mechanical principle is the same: Depress the clutch pedal and the clutch is released. How?

Whether the clutch-pedal system is operated hydraulically or by cable, it moves a release fork that pivots on the bellhousing. The pivoting action moves the end of the fork toward the pressure plate. A throwout bearing (also called a clutch-release bearing) at the end of the release fork applies even pressure to the diaphragm spring and the pressure plate moves back, releasing the clutch disc. Let the clutch out, and the pressure on the spring releases and the clamping force on the disc returns.