Centrifugal clutch

It is often used in mopeds, underbones, lawn mowers, go-karts, chainsaws, mini bikes, and some paramotors and boats to keep the engine from stalling when the output shaft is slowed or stopped abruptly, and to remove load when starting and idling.

The most common types have friction pads or shoes radially mounted that engage the inside of the rim of a housing.

When the central shaft spins fast enough, the springs extend, causing the clutch shoes to engage the friction face.

This type can be found on most home-built karts, lawn and garden equipment, fuel-powered model cars, and low power chainsaws.

This results in a fair bit of waste heat, but over a broad range of speeds, it is much more useful than a direct drive in many applications.