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 in mopeds, under bones, lawnmowers, 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. It has been superseded for automotive applications by fluid coupling and automated manual transmissions.
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.
More Resources: What is a Clutch?
A centrifugal clutch works, as the name suggests, through centrifugal force. 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.
As we have experienced since childhood in roundabouts on playgrounds, when a mass is rotating/spinning a force is generated that points away from the axis of rotation and is known as centrifugal force. The faster the rotation gets, the stronger that force gets and that is why it is so difficult to stay in roundabouts that are spinning quickly.
The operation of the centrifugal clutch is based precisely on the generation of this centrifugal force. In particular, the rotating shaft is connected to the crankshaft of the engine and arranged in the middle of the clutch.
The outer housing is positioned concentrically and connected to the driven shaft. As the engine speed increases, the speed of the drive shaft increases, forcing the shoes installed on the inside of the assembly to expand and reach the inside wall of the drum.
Both the inside of the drum and the outside of the shoe are made of materials with high friction so that a reliable engagement is possible, similar to braking. However, this also causes high temperatures if the engagement/disengagement action occurs more frequently than intended.
As soon as the engine speed drops again, the clutch is disengaged immediately so that the driven shaft no longer receives any rotational movement energy. This helps prevent the engine from stalling when the load is overwhelming and the engine has trouble handling it and makes overall operation safe for both the systems and the user.
Centrifugal clutches can have two, three, four, five, or even six shoes that follow a symmetrical positioning on the drive shaft. In order for them to expand in a controlled manner and in relation to engine speed, manufacturers use expansion springs to compensate for this expansion.
Manufacturers can use different spring strengths and lengths to achieve specific engagement and disengagement points for their centrifugal clutch, whereby the engagement should generally be maintained in the optimum engine torque range.
This means that not every centrifugal clutch is ideal for every type of engine and that both must be considered and optimized together in order to achieve the best possible results.
These are sliding shoes that slide in the guideways. It consists of friction lining at the end and this friction lining contacts the drum during the engagement.
Spring is a controlling element here, it is used to release the clutch when the engine is turning more slowly.
The spiders are mounted on the drive shaft (motor shaft) or the motor shaft. The spiders are evenly distributed. Equally spaced means, if there are four guides, each guide is 90 degrees apart. The shoes are held between these guides and each guide holds a spring.
The outer surface of the sliding shoes is provided with friction lining. It helps hold the inside surface of the drum in place.
The clutch drum serves as a housing that encloses all parts of the clutch, including sliding shoes, guides, springs, etc. It is connected to the driven shaft of the transmission system or to chains or belts.
There are several reasons to choose the centrifugal clutch over alternative types:
There are also several disadvantages of centrifugal clutch:
Centrifugal clutches that correctly transmit a movement with centrifugal force are mainly used in industrial machines such as sweepers, mowers, chain saws, generator sets, motor pumps, lawnmowers, or fans. They are also used in cooling systems and mini karts.
While friction clutches offer numerous advantages, they are not always suitable for every application. Here are some considerations to keep in mind when planning to use a centrifugal clutch:
A centrifugal clutch is a mechanical device that 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 works, as the name suggests, through centrifugal force. 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.
Advantage:
Centrifugal clutches, which use centrifugal force to convey a movement correctly, are primarily applied to industrial machineries such as sweepers, mowers, chainsaws, generator sets, motor pumps, lawnmowers or fans. Moreover, they are also applied to refrigeration systems and mini-karts.
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.
NORAM centrifugal clutches are designed to fit engines ranging from fractional horsepower up to 50 HP applications.
A clutch starts to engage around 2,000 rpm and will lock up around 2,600 rpm. Driving at full throttle gives the clutch a chance to cool down. Full throttle locks the shoes in the clutch against the drum.
Disadvantages of Centrifugal Clutch:
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.
Improper installation of the centrifugal clutch can result in its failure as quickly as in a couple of minutes. Still though, even if installed properly, it won’t last more than five years maximum.
Your clutch may be overheating due to several reasons. One of the most common reasons is a lack of lubrication. If your clutch is not lubricated properly, there is no agent that helps to reduce friction and disseminate heat.
Torque converters are great for lower-end torque, as they have the ability to adjust the gear ratio depending on the engine’s RPM. This makes it ideal for heavier or off-road go-karts. On the other hand, a regular clutch maintains the same gear ratio all the time.
If the clutch engages too quickly, back the adjustment screw off a half-turn. If engagement is too high or slow, tighten the adjusting screw up a bit.
a semi- centrifugal clutch uses lighter pressure plate springs for a given torque carrying capacity so that the engagement of the clutch in the lower speed range becomes possible. The centrifugal force supplements the necessary extra clamping thrust at higher speeds.
