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A Centrifugal clutch is a clutch that works off of rotational motion rather than lateral. In an automobile clutch with a manual transmission, the clutch is deactivated with a foot pedal which in turns pushes on a fulcrum, which retracts the pressure plate, causing the engine and transmission to separate from power, and the driver able to change gears.

A centrifugal clutch works by centrifugal force. The input of the clutch is connected to the engine crankshaft while the output may drive a shaft, chain, or belt. As engine RPM increases weighted arms in the clutch force the clutch to engage. The most common type has friction pads or shoes radially mounted that engage the inside of the rim of the housing. On the center shaft there are an assorted amount of extension springs, which connect to a clutch shoe. When the center shaft spins fast enough, the springs extend causing the clutch shoes to engage the friction face. It can be compared to a drum brake in reverse. This type can be found on most home built karts, lawn and garden equipment, and low power chainsaws. Another type used in racing karts has friction and clutch disks stacked together like a motorcycle clutch. The weighted arms force these disks together and engage the clutch.

When the engine reaches a certain RPM, the clutch activates, working almost like a Continuously variable transmission. As the load increases the rpm drops, disengaging the clutch, letting the rpm rise again and reengaging the clutch. If tuned properly the clutch will tend to keep the engine at or near the torque peak of the engine. These results in a fair bit of waste heat, but over a broad range of speeds it is much more useful then a direct drive in many applications.

Centrifugal clutches are often used in mopeds, underbones, lawnmowers, battlebots, go-karts, chainsaws and mini bikes to:

• keep the internal combustion engine from stalling when the blade or weapon is stopped abruptly
• provide low load during starting
• allow engine to idle

The centrifugal clutch was invented by Thomas Fogarty, who also invented the balloon catheter.

• Saxomat

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