What is a Centrifugal Clutch?

What is a Centrifugal Clutch?

A centrifugal clutch is a mechanical device which is used on driven rotary equipment. Most commonly used with a combustion engine, the clutch can be used to automatically transmit the torque from the drive to the driven equipment giving a “soft start” with no load engagement.

A centrifugal clutch is an automatic clutch that uses centrifugal force to operate. The output shaft is disengaged at low rotational speed and engages more as speed increases. It is often used to keep the engine from stalling when the output shaft is slowed or stopped abruptly, and to remove load when starting and idling. It has been superseded for automotive applications by the fluid coupling.

Centrifugal Clutch

By using this type of clutch between the drive and the driven equipment the speed at which the mechanical driven shaft engages can be controlled. As the engine speed is increased to or above the set engagement speed of the centrifugal clutch the mechanical drive will become engaged.

This enables the operator to run the engine at a designated idling speed without driving the equipment, thus allowing the engine to reach its optimal torque before experiencing load.

How Does A Centrifugal Clutch Work?

A centrifugal clutch works, as the name suggests, through centrifugal force. The key components of a centrifugal clutch are the hub, flyweights (clutch shoes), springs, linings and housing. The centrifugal force, created by the revolutions of the engine is transmitted through two or more flyweights.

The clutch can be driven in a number of ways depending upon the design of the machinery. One of the most common methods is by mounting the clutch onto the parallel or taper crankshaft of the engine. When the crankshaft rotates the shaft of the clutch rotates at the same speed as the engine. The rotation of the hub forces the shoes or flyweights outwards until they come into contact with the clutch drum, the friction material transmits the torque from the flyweights to the drum.

The drive is then connected. The springs, flyweights and the friction material are responsible for determining the speed at which the clutch engages. Depending on the design of the machine the output from the clutch can be one of a variety drives, including but not limited to shaft, pulley, sprocket or flange.

Different Parts of Centrifugal Clutch:

There are so many parts present in the Centrifugal Clutch. From that, the main parts are discussed below:

  1. Shoes
  2. Spring
  3. Spider or Guides
  4. Friction Lining
  5. Drum
Centrifugal Clutch

Shoes:

Shoes can be used as friction consumers. It is mainly a sliding type of thing. These shoes are attached between the guides. In guideways, the shoes used to slide. At the end of the shoes, the shoes have friction lining. At the time of engagement, with the drum, this friction lining can be used to make contact.

Spring:

Spring is a controlling element here. It can be usually used at a time of lower speed. Spring is attached to each shoe. With the help of this spring, shoes are attached with the guide.

When the engine used to rotate at a low speed then the clutch is needed to be disengaged. Here the Spring disengages the clutch. Otherwise, spring holds the shoe in the initial position of it since the proper speed is not achieved. Higher spring indexed springs are required when the engaging speed is needed to be the change of the clutch.

Spider or Guides:

The spider is placed on the motor shaft or on the driver (engine) shaft. The space between spiders is equal. This space is equal means, the distance between each guide is the same.

As an example, if it is considered that if there are three guides present then for each guide, the next guide is separated by 90 degrees from that. Between these guides, the shoes are kept to consume the frictions between these guides and each guide consists of a spring to disengage the clutch.

Friction Lining:

The Friction lining is a part of the sliding shoes. Friction lining works in the same principle as the friction plate of a simple clutch works. With the end of the outer surface of shoes, this friction lining can be attached.

Friction lining transmits torque. It helps to make a grip on the drum’s inner surface. And it avoids the direct contact of the sliding shoes by the drum. It reduces the tear and wear of the sliding shoes.

Drum:

The Drum works as the housing component in the clutch. All the clutch parts, like guides, sliding shoes, springs, friction lining and others are surrounded by the Drum. The drum is attached with the driven shaft of the belt or chain or the transmission system.

Working Principle of Centrifugal Clutch:

Centrifugal clutch mainly works on the principles of two forces. They are Centrifugal Force and Friction Force. Centrifugal Force is that special kind of force that creates on a rotating body and it is the force that pulls the body which is rotating from its center.

On the other hand, the Friction Force is the force that creates between two surfaces of other bodies when they are moving from the opposite side of each other.

Centrifugal clutch can be used to connect the accelerated load with the power sources (turbine, motor, engine and others). According to the amount of Centrifugal force made by a driving member (motor or engine), the working of the Centrifugal clutch depends. Centrifugal clutch mainly attaches other clutches or engages the driven shaft with the clutches.

When the engine starts to rotate then the Centrifugal force produces. This centrifugal force turns the driveshaft. This force also activates the transmission depending on the enhancement of the engine rpm.

The size of the clutch is developed according to the load but in that case, the motors’ horsepower cannot be considered anytime. Alongside, a small-sized motor can also be utilized in order to develop or bring the maximum output regarding the torque. Also, the size of the gear reducer is small.

The Centrifugal force can also be used to push the sliding shoes outward. Then the friction lining of the shoes makes a connection with the drum’s inner surface. So, the drum starts to move. The drum is then attached to the driven shaft. At first, it helps to transmit the power to the transmission shaft from the engine shaft and then to the load.

Centrifugal clutch makes the current draw to be the minimum and the torque is the maximum. Due to less amount of heat emissions the clutch plate does not slip through which the load can be accelerated. Alongside this, the motor is also safe due to the low amount of heat dissipation.  Oftentimes it is found that due to high heat, motor JA burnt and that is not good for any machinery around the manufacturing industry.

Advantages of Centrifugal Clutch:

There are many reasons present to choose the centrifugal clutch as an alternative one. These reasons can be counted as the advantages of the Centrifugal clutch. They are as follows:

  • Centrifugal clutch does the work of engaging and disengaging automatically. So, there is no necessity or requirement of any other kind of mechanical part to control the peak speed of the engine. The working principle of the centrifugal clutch is mainly based on the law of physics.
  • In comparison with other clutches, the cost of the Centrifugal clutch is much lower. Relatively the Centrifugal clutch is less expensive. In the case of the Centrifugal clutch, fewer parts are involved. No battery or extra component is needed to assist the Centrifugal clutch to perform the function properly.
  • The servicing and maintenance cost of the centrifugal clutch is low. As the construction and primary design is good so there is a little chance of breaking down or wearing away the system. As the construction and design of this clutch are sound at the initial stage so there are minimal chances present to be damaged. So, users of this clutch have to expend a little money for maintenance and servicing. Therefore, it is more cost-effective and too good to use the centrifugal clutch and it is economically good for users.
  • Overloading and abrupt starting can create a burden on the engine which causes damage to the engine. In the case of a centrifugal clutch, it is better and safer than the others with load and progressive engagement. Centrifugal clutch is mainly specialized to perform shock less and smooth acceleration.
  • The centrifugal clutch can control the speed of the engine. This clutch has a greater progressive engagement and this feature helps in increasing the torque, a twisting force moving toward the load from the engine.
  • The centrifugal clutch having the feature of greater engagement and speed control that enhances the longer lifespan and excess energy accumulation on the startup.

Disadvantages of Centrifugal Clutch:

There are so many disadvantages of the Centrifugal Clutch present. They are as follows:

  • Though the centrifugal clutch has many benefits yet this clutch is not suitable for all applications on all occasions.  The user must be aware of the fact of lack of experience in applications of a centrifugal clutch.
  • The transmission power of the centrifugal clutch has limitations because of slippage. In the case of an engine with a low RPM, a centrifugal clutch is not suitable for that one because of the overheating problem. More heat can be produced due to friction between shoes and clutch drum. This problem of overheating can damage the clutch due to slippage and loss of power.
  • Various sizes of clutch create a different amount of peak speed. The clutch is smaller in size and produces a faster speed. This happens due to the centrifugal force that is needed to be engaged.
  • The clutch is activated when an engine reaches a particular speed. If the engine wants to attain a certain speed the clutch does not work properly. If loading capacity goes beyond the capability of the clutch loses its performance which leads to slippage. Due to this problem engine cannot perform properly causing damage to the engine. So, the centrifugal clutch is suitable for an engine having high speed but not for a lower speed engine. So, the centrifugal clutch protects driven equipment and saves the engine with a vast range of speed.
  • Centrifugal clutch cannot create high torque.
  • So much power loss is present, during the slipping and friction.
  • In the case of vehicles, so many heats get produced during bad driving habits. This overheating may damage the clutch completely.

Applications of Centrifugal Clutch:

There are many applications of the Centrifugal Clutch is present. They are as follows:

  • Centrifugal clutch is generally used in vehicles.
  • Centrifugal clutch is widely used in industrial applications like machinery, mining, military, manufacturing purposes.
  • In chemical industries, the Centrifugal clutch is used in mixers.
  • Used in lawn movers, chain saw.
  • Used in scooters, go-karts, and mopeds.
  • During stalling, in paramotors and boats, a Centrifugal clutch is used to keep this stalling and during idling and start of the disengagement of the loads are done by Centrifugal clutch.

FAQ

A centrifugal clutch is a mechanical device which is used on driven rotary equipment. Most commonly used with a combustion engine, the clutch can be used to automatically transmit the torque from the drive to the driven equipment giving a “soft start” with no load engagement.

When the crank shaft rotates the shaft of the clutch rotates at the same speed as the engine. The rotation of the hub forces the shoes or flyweights outwards until they come into contact with the clutch drum, the friction material transmits the torque from the flyweights to the drum.

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