How Clutches Work

You might be startled to learn that a manual gearbox car has more than one clutch if you drive one. It turns out that people who drive cars with automatic transmissions also have clutches. In fact, you probably use or see clutches in a lot of products every day. A clutch is a common feature of chain saws, many cordless drills, and even certain yo-yos.

How Clutches Work

This article will explain why you need a clutch, how your car’s clutch functions, and several interesting—and possibly unexpected—locations where clutches can be located.

Cars and other equipment with two spinning shafts benefit from clutches. Usually, a motor or pulley drives one of the shafts while another device is driven by the other shaft. The clutch joins the two shafts so that they can be disconnected and spun at various speeds or locked together and spun at the same speed.

A clutch is necessary in a car because, unlike the wheels, the engine rotates continuously. The wheels must be somehow uncoupled from the engine for an automobile to stop without damaging the engine. By regulating the slippage between them, the clutch enables us to smoothly engage a spinning engine to a transmission that is not spinning.

Knowing a little bit about friction, which is a measurement of how difficult it is to move one thing over another, is helpful in understanding how a clutch operates. Every surface has microscopic peaks and valleys; even very smooth surfaces have them. These peaks and valleys are what produce friction. The harder it is to slide the object, the bigger these peaks and valleys appear.

Friction between a clutch plate and a flywheel is how a clutch operates. In the section after this, we’ll examine how these components interact.

Fly Wheels, Clutch Plates and Friction

In a car’s clutch, a flywheel connects to the engine, and a clutch plate connects to the transmission.

Exploded View of a Clutch

In a manual transmission vehicle, the clutch disc and pressure plate are pressed against each other by the flywheel and pressure plate when the clutch pedal is depressed. The engine and transmission input shafts get locked to one another as a result, spinning at the same speed.

The friction between the clutch plate and the flywheel and the force the spring exerts on the pressure plate determine how much force the clutch can withstand. The friction force in the clutch operates similarly to the blocks mentioned in the How Brakes Work section on friction, with the exception that the spring forces against the clutch plate rather than the block being pressed into the ground by weight.

How a Clutch Engages and Releases

The release fork is pushed against by a cable or hydraulic piston when the clutch pedal is depressed. In turn, this pushes the middle of the diaphragm spring up against the release bearing, which releases the engine from the transmission during gear shifts. The pressure plate is pulled away from the clutch disc while the centre of the diaphragm spring is forced in by a row of pins on the exterior of the spring. The clutch is now freed from the rotating engine.

Take note of the clutch plate’s springs. The transmission is protected by these springs from the shock of the clutch engaging.

Although this design typically functions rather well, there are a few shortcomings. In the parts that follow, we’ll examine typical clutch issues as well as some additional clutch applications.

Common Problems

Your car and garage likely have a variety of additional clutches.

The clutches of an automatic transmission are numerous. These clutches engage and disengage various sets of planetary gears, which consist of an orbiting gear in the center that serves as the drive gear. In an automatic transmission, pressurized hydraulic fluid is used to move each clutch. Springs cause the clutch to release when the pressure decreases. The interior and exterior of the clutch are lined with uniformly spaced ridges known as splines that lock onto the gears and the clutch housing. More information about these clutches may be found in How Automatic Transmissions Work.

An electromagnetic clutch is found on a car’s air conditioning compressor. With the engine running, the compressor can turn off thanks to this. The clutch engages when current passes through a magnetic coil inside the clutch. The clutch disengages when the current ceases, which happens when you switch off your air conditioner.

The temperature of the fluid drives the viscous clutch, which is found in the majority of vehicles with an engine-driven cooling fan. This clutch is located in the airflow passing through the radiator at the fan’s hub. The clutch fluid thickens as it warms up, forcing the fan to turn more quickly to keep up with the engine’s rotation. As the fan runs slowly and the clutch fluid stays cold when the car is cold, the engine warms up fast to the proper operating temperature.

Both limited slip differentials and viscous couplings, which use clutches to help boost traction, are common in automobiles. One wheel spins quicker than the other when your car is turning, making the vehicle difficult to control. That is compensated for by the slip differential’s clutch. The clutch engages to slow one wheel down and bring it into balance with the other three when it spins more quickly than the others. Your wheels can spin when you drive over water or ice spots.

Centrifugal clutches are a feature of gas-powered chainsaws and weed eaters that allow the chains or strings to cease spinning without having to switch the engine off. Centrifugal force is used to automatically operate these clutches. The engine crankshaft is linked to the input. The output can power a shaft, chain, or belt. Weighted arms swing out as the revolutions per minute rise, forcing the clutch to engage. Lawn mowers, go-karts, mopeds, and mini-bikes all frequently use centrifugal clutches. Centrifugal clutches are used in the manufacturing of some yo-yos as well.

Clutches are useful and essential for a variety of uses. Check out the links below for more information on clutches and related subjects.

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