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Centrifugal Force and Centrifugal Clutch

Centrifugal Force usually refers to a fictional or pseudo force that seems to give an outward "center-fleeing" acceleration to an object traveling in a circle. Let us imagine a book on a slippery dashboard in a moving car. To a passenger in the car the book appears stationary until the driver makes a sharp turn to the left. At this point the book appears to the passenger to accelerate to the right. The passenger may be inclined to conclude that some force is accelerating the book away from the center of the car's curved path. Actually the book is not accelerating. Someone outside the car would observe the book from going in a straight line, and the car moving out from underneath it. This is an example of Newton's First Law of Motion: since there is no force acting on the book it moves in a straight line. At the same time, the passenger feels as though there is something pushing him into the right side of the car. What the passenger is actually experiencing is the right side of the car pushing against him, causing the passenger to travel in a circular path with the car. The passenger may conclude from his frame of reference that there is a centrifugal force causing him and the book to slide toward the outside of the curve. The outside observer would conclude from his frame of reference that there is no force acting on the book and the only force acting on the passenger is normal force provided by the surfaces of the car. To the outside impartial observer, the motion of the book is because of the book's inertia, and the centrifugal force is not a real force.


Centrifugal Forces come into effect when an object is continuously going around in a circle, such as when a ball, attached to a spring, which is attached to a nail in a board, is going around in a circle. Centripetal force is applied onto the ball. Centrifugal force is applied to the spring. The centripetal force is the force that is applied on the ball causing it to move inwards. The centrifugal force is the force that is applied on the spring making it stretch outwards. If the centrifugal force is too large, the spring connecting the ball to the nail will break and the ball to fly off in a straight line tangent to the circular path. The faster the ball spins, which is called Rotations Per Minute (RPM), the farther the ball will move outward from the nail, which brings us to the Real Life Application. Centrifugal force is harnessed in a clutch used in go-karts.

A centrifugal clutch is used on most racing go-karts. Centrifugal clutch is the common name given to a clutch which uses centrifugal forces to engage. It is what connects the engine's drive shaft to the drive axle which spins the wheels. The centrifugal clutch and the drive axle have sprockets which spin a chain, which will spin the wheels.

A centrifugal clutch uses a spring, pivot, hub, and shoe that enable centrifugal force to engage the clutch.

Observe the picture of the Centrifugal Clutch. Inside of the centrifugal clutch are pads (also known as shoes) which move outward as the drive shaft of the engine spins faster, just like with the ball and nail explanation stated before. Once the shaft is spinning fast enough, the pads start to push on the inside of the hub on the clutch. Once the hub of the clutch has started spinning, the sprocket which is attached to the hub starts spinning, which in turn, spins the drive chain, and the go-kart moves forwards.

During this time the pads are slipping somewhat inside of the hub, which makes it possible for the vehicle to be run at different speeds. Once the maximum rotation speed (RPM) is reached by the engine, there will no longer be any slipping between the clutch shoes and the hub. Maximum speed of the vehicle has been reached at this time. Centripetal and centrifugal forces are at their limit here, if excessive centrifugal forces are achieved, the clutch will blow apart, as in the ball and nail explanation in which the spring broke and the ball flew away in a straight line.


Why do some racing organizations require a safety shield to be secured around the centrifugal clutch of the racing vehicle?

Answer: The safety shield is in place to protect the driver and spectators from flying debris if the centrifugal forces inside a centrifugal clutch cause the clutch to blow apart.

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