Clutch
To stop the transfer of power, the friction disk is moved away from the flywheel by means of a lever mechanism.
Drag racing cars use multi-plate clutches to control the rate of power transfer to the wheels as the vehicle accelerates from a standing start.
[6][7] In addition to their use in heavy manufacturing equipment, single-revolution clutches were applied to numerous small machines.
In tabulating machines, for example, pressing the operate key would trip a single revolution clutch to process the most recently entered number.
[9] Similarly, in teleprinters, the receipt of each character tripped a single-revolution clutch to operate one cycle of the print mechanism.
[10] In 1928, Frederick G. Creed developed a single-turn wrap spring clutch that was particularly well suited to the repetitive start-stop action required in teleprinters.
[11] In 1942, two employees of Pitney Bowes Postage Meter Company developed an improved single turn spring clutch.
[12] In these clutches, a coil spring is wrapped around the driven shaft and held in an expanded configuration by the trip lever.
These clutches have long operating lives—many have performed tens and perhaps hundreds of millions of cycles without the need of maintenance other than occasional lubrication.
Most cars and trucks with a manual transmission use a dry clutch, which is operated by the driver using the left-most pedal.
The motion of the pedal is transferred to the clutch using mechanical linkage, hydraulics (master and slave cylinders) or a cable.
A "neutral" gear position is provided, so that the clutch pedal can be released with the vehicle remaining stationary.
[17] Older belt-driven engine cooling fans often use a heat-activated clutch, in the form of a bimetallic strip.
When the temperature is low, the spring winds and closes the valve, which lets the fan spin at about 20% to 30% of the crankshaft speed.
Racing motorcycles often use slipper clutches to eliminate the effects of engine braking, which, being applied only to the rear wheel, can cause instability.
