The clutch connects the two shafts so that they can either be locked together and spin at the same speed, or be decoupled and spin at different speeds. In a car, you need a clutch because the engine spins all the time, but the car's wheels do not.
In order for a car to stop without killing the engine, the wheels need to be disconnected from the engine somehow. The clutch allows us to smoothly engage a spinning engine to a transmission that is not spinning by controlling the slippage between them. To understand how a clutch works, it helps to know a little bit about friction , which is a measure of how hard it is to slide one object over another.
Friction is caused by the peaks and valleys that are part of every surface — even very smooth surfaces still have microscopic peaks and valleys. The larger these peaks and valleys are, the harder it is to slide the object.
A clutch works because of friction between a clutch plate and a flywheel. We'll look at how these parts work together in the next section. In a car's clutch, a flywheel connects to the engine , and a clutch plate connects to the transmission. When your foot is off the clutch pedal in a manual car, springs push the pressure plate against the clutch disc, which in turn presses against the flywheel.
This locks the engine to the transmission input shaft, causing them to spin at the same speed. The amount of force the clutch can hold depends on the friction between the clutch plate and the flywheel, and how much force the spring puts on the pressure plate. The friction force in the clutch works just like the blocks described in the friction section of How Brakes Work , except that the spring presses on the clutch plate instead of weight pressing the block into the ground.
When the clutch pedal is pressed, a cable or hydraulic piston pushes on the release fork. This in turn presses the release bearing , which disengages the engine from the transmission during gear shifts, against the middle of the diaphragm spring. As the middle of the diaphragm spring is pushed in, a series of pins near the outside of the spring causes the spring to pull the pressure plate away from the clutch disc.
This releases the clutch from the spinning engine. Note the springs in the clutch plate. These springs help to isolate the transmission from the shock of the clutch engaging. This design usually works pretty well, but it does have a few drawbacks. We'll look at common clutch problems and other uses for clutches in the following sections. From the s to the s, you could count on getting between 50, and 70, miles 80, and , kilometers from your car's clutch.
Clutches can now last for more than 80, miles , kilometers if you use them gently and maintain them well. If not cared for, clutches can start to break down at 35, miles 56, kilometers. Trucks that are consistently overloaded or that frequently tow heavy loads can also have problems with relatively new clutches. The most common problem with clutches is that the friction material on the disc wears out. The friction material on a clutch disc is very similar to the friction material on the pads of a disc brake or the shoes of a drum brake — after a while, it wears away.
When most or all of the friction material is gone, the clutch will start to slip, and eventually it won't transmit any power from the engine to the wheels.
The clutch only wears while the clutch disc and the flywheel are spinning at different speeds. When they are locked together, the friction material is held tightly against the flywheel, and they spin in sync. It's only when the clutch disc is slipping against the flywheel that wearing occurs. So, if you are the type of driver who slips the clutch a lot, you'll wear out your clutch a lot faster.
Sometimes the problem is not with slipping, but with sticking. If your clutch won't release properly, it will continue to turn the input shaft. This can cause grinding, or completely prevent your car from going into gear. Some common reasons a clutch may stick are:. A "hard" clutch is also a common problem.
All clutches require some amount of force to depress fully. If you have to press hard on the pedal, there may be something wrong. Sticking or binding in the pedal linkage, cable, cross shaft, or pivot ball are common causes. Sometimes a blockage or worn seals in the hydraulic system can also cause a hard clutch.
In fact, there are several different types of clutches, which include:. Frictional forces are what clutches rely on to operate.
Frictional clutches connect one moving member to another one that is moving at a different speed, or not at all, to get it moving at the same speed so that there is no slippage.
Various materials are used to create this friction. They include:. You'll mostly see ceramic materials used in racing or heavy-duty hauling situations, though this material can increase wear and tear on the flywheel and pressure plate. With wet clutches, you find the use of composite paper. Because these types of clutches tend to use an oil bath or flow-through cooling method, they have less wear than ceramic material. Multiple plate clutches have more than one driving member, making them ideal for racing cars such as Formula 1, Indy , and club racing as well.
In drag racing vehicles, a lot of abuse goes to the clutch, which is why they often have this type of clutch. It can also be found in motorcycles and diesel engines with mechanical transmissions. Additionally, you might find one in a car with an electronically controlled all-wheel-drive system and in some transfer cases too.
A cone clutch has a conical shape, and its taper means that it approaches or recedes more slowly than a disc-type clutch. What this translates to is that speeds of the shift hub and gear wheel are synchronized to give you smoother shifting when you change gears. It's most likely that you'll find a centrifugal clutch in a vehicle such as a moped or machinery like chainsaws, where the speed of the engine defines the state of the clutch.
When the rpms of the engine rise above or fall below a certain level, it will either engage or disengage the clutch using centrifugal force. A wet clutch system differs from a dry clutch in that it is immersed in a cooling fluid that lubricates it to keep it clean and extend its life.
It's important to note however, that this type of clutch will lose energy because they tend to be slippery. Stacking multiple clutch discs can help to compensate for this slippage. A dry clutch, on the other hand, uses friction, as it isn't bathed in liquid. It is possible to get up to 80, miles out of your clutch, shares AAMCO, but you'll need to treat it well for this to happen.
Some of the most common clutch problems are:. The main function of the pressure plate is to establish even contact with the driven plate facing through which the pressure springs can exert a sufficient force to transmit the full torque of the engine. The pressure plate presses the clutch plate on to the flywheel from its machined surface. Between the pressure plate and clutch cover assembly, pressure springs are fits. The pressure will be withdrawn from the flywheel whenever release levers depress by the toggle or release levers pivots accordingly.
The clutch cover assembly bolts to the flywheel. It consists of a pressure plate, release lever mechanism, clutch cover, and pressure springs. Generally, the clutch plate revolves with the flywheel. However, when the clutch has disengaged, the flywheel, as well as the pressure plates, are free to rotate independently from the driven plate and driving shaft. These pivots on pins to the clutch cover, their outer ends locate and positions on pressure plate legs, and the inner ends are projecting towards the clutch shaft.
A careful and accurate adjustment of the release mechanism is one of the most important factors governing the performance of a clutch assembly. It is a component of the gearbox. Since it is a splined shaft to the hub of the clutch plate, which is sliding on it. One end of the clutch shaft attaches to the crankshaft or flywheel and the other end connects to the gearbox or forms a part of the gearbox.
A Clutch is defined as a system that is used to connect or disconnect the engine from the rest of the transmission elements. It is located between the engine and gearbox. During normal running and stationary position, it is always in the engaged condition.
The clutch disengages when the driver processes the clutch pedal. The clutch disengages for starting, changing gears, stopping, and idling. When the clutch engages, the engine will connect to the transmission, and power flows from the engine to rear wheels through a transmission system When the clutch disengages by pressing the clutch pedal, the engine will disengage from the transmission.
Thus, the power does not flow to rear wheels while the engine is still running. The clutch is a device that is necessary to transmit power from the engine to the wheels of the vehicle by engaging the engine to the transmission system gradually without giving the jerks to the body of the vehicle.
The clutch works on the principle of friction. Now, an external force is applied to the flange D so that it comes in contact with flange C. As soon as the contact is made, they are united due to friction between them and the flange D starts rotating with flange C.
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