Centrifugal clutch

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Centrifugal clutch

A centrifugal clutch is a clutch

Clutch

A clutch is a mechanism for transmitting rotation, which can be engaged and disengaged. Clutches are useful in devices that have two rotating shafts....
that uses centrifugal force

Centrifugal force

In classical mechanics, centrifugal force is an outward force associated with rotation. Centrifugal force is one of several so-called pseudo-forces , so named because, unlike Fundamental interaction, they do not originate in interactions with other bodies situated in the environment of the particle upon which they act....
to connect two concentric shafts, with the driving shaft nested inside the driven shaft.

The input of the clutch is connected to the engine crankshaft

Crankshaft

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Encyclopedia

A centrifugal clutch is a clutch

Clutch

A clutch is a mechanism for transmitting rotation, which can be engaged and disengaged. Clutches are useful in devices that have two rotating shafts....
that uses centrifugal force

Centrifugal force

Crankshaft

The crankshaft, sometimes casually abbreviated to crank , is the part of an engine which translates reciprocation linear piston motion into rotation....
while the output may drive a shaft, chain, or belt. As engine RPM increases, weighted arms in the clutch swing outward and force the clutch to engage. The most common types have friction pads or shoes radially mounted that engage the inside of the rim of a 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

Drum brake

A drum brake is a brake in which the friction is caused by a set of Brake shoe or Brake pad that press against the Brake lining of a rotating drum....
in reverse. This type can be found on most home built karts, lawn and garden equipment, fuel powered model cars 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

Continuously variable transmission

A continuously variable transmission is a Transmission which can change steplessly through an infinite number of effective gear ratios between maximum and minimum values....
. 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. 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.

Centrifugal clutches are often used in moped

Moped

Mopeds are a class of low-powered motorized vehicle, generally two or three wheeled. Moped classification is designed to allow the use of small motorized vehicles seen as not requiring the safety restrictions and license requirement that larger motorcycles are subject to....
s, underbone

Underbone

Underbones or Underbone Motorcycles are a class of small motorcycles based on a singular tube frame, the 'underbone' supporting the vehicle....
s, lawnmowers, battlebots, go-karts, chainsaw

Chainsaw

A chainsaw is a portable mechanical, motorized saw. It is used in logging activities such as felling, limbing, and Log bucking; by tree surgeons to fell trees and remove branches and foliage; to fell snags and assist in cutting firebreaks in wildland fire suppression, and to harvest Wood fuel#Firewood....
s, and mini bikes to:

keep the internal combustion engine
Internal combustion engine

The internal combustion engine is an engine in which the combustion of a fuel occurs in a combustion chamber inside and integral to the engine. In an internal combustion engine it is always the expansion of the high temperature and pressure gases that are produced by the combustion which apply force to the movable component of the engine, such as...
from stalling when the blade
Blade

A blade is the flat part of a tool, weapon, or machine that normally has a cutting edge and/or pointed end typically made of a flaking stone, such as flint, or metal, most recently steel....
or weapon
Weapon

A weapon is a tool used to apply or threaten to apply force for the purpose of hunting, attack or defense in combat, subduing enemy personnel, or to destroy enemy weapons, equipment and defensive structures....
is stopped abruptly
provide low load during starting
allow engine to idle

Thomas Fogarty

Thomas Fogarty , is a professor of surgery at Stanford University. He is also an inventor of medical devices and a vintner....
, who also invented the balloon catheter

Balloon catheter

A balloon catheter is a type of "soft" catheter with an inflatable "balloon" at its tip which is used during a catheterization procedure to enlarge a narrow opening or passage within the body....
, is most often credited with first inventing the centrifugal clutch in the 1940s, although automobiles were being manufactured with centrifugal clutches as early as 1936 (Dr Fogarty was born in 1934).

Centrifugal clutch

See also