Clutches:

A clutch is a mechanical device that engages and disengages the power transmission means shaft, especially from the driving shaft to the driven shaft. When we have to change the gear in the transmission system then for that time we have to use the clutch. Clutch plate is defined as the mechanism to transmit rotary motion from driving shaft to drive Shaft as and when required without stopping the driving shaft. A layout of transmission of system which includes location of clutch.

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A clutch is a mechanism which enables the rotary motion of one shaft to be transmitted at will to second shaft, whose axis is coincident with that of the first.

The purpose of clutch:

(a) To transmit power smoothly.
(b) Once the clutch is engaged, the clutch must transmit power without slipping.
(c) During initial pick up of vehicle from stationary to moving the engine is running but the vehicle is stationary.
(d) To overcome the self-inertia of vehicle.
(e) For gradual engagement of rotary motion from the engine to the gear box shaft.
(f) These are also used to disengage the drive from engine to gear box for changing of different gears.
(g) At the time of stopping of vehicle the clutch is utilized to disengage engine from drive wheels and enable smooth stopping of the vehicle.
(h) Clutch also takes the care of speed and torque fluctuation for engine crankshaft to gear box input shaft since clutch is made up from friction material.

Working of clutch:

The clutch is located between the engine and gear box. When the clutch is engaged, the power flows from the engine to the rear wheels through the transmission system and the vehicle moves. When the clutch is disengaged, the power is not transmitted to the rear wheels and the vehicle stops while the engine is still running. Clutches are useful in devices with two rotating shafts one will act as a driver and the other is a driven shaft. One of the shafts is typically driven by a motor or pulley and the other shaft is driving another device.

Functions of a Clutch:

 

1. 1. To permit engagement or disengagement of a gear when the vehicle is stationary, and the engine is running.

1. 1. To transmit the engine power to the road wheels smoothly without shock to the transmission system while setting the wheel in motion.

1. 1. To permit the engaging of gears when the vehicle is in motion without damaging the gear wheels.

Characteristics of good clutch:

 

1. 1. It should engage gradually to avoid sudden Jerks.

1. 1. It should be easily operated.

1. 1. It should be dynamically balanced.

1. 1. It should be free from slip when engaged.

1. 1. It should be as small as possible so that it will occupy minimum space.

1. 1. The wearing surfaces should have long life.

1. 1. It should be easily accessible and have simple means of adjustment.

1. 1. It should be able to dissipate large amount of heat which is generated during the clutch operation due to friction.

Principle of operation of a clutch:

The clutch principle is based on friction. When two friction surfaces are brought in contact with each other and pressed, they are united due to friction between them. If one is revolved, the other will also revolve.

The friction between the 2 surfaces depends upon:

(i) Area of surface. (ii) Pressure applied upon them. (iii) Coefficient of friction of the surface materials.

One surface is considered as driving member and the other as driven member. The driving member is kept rotating. When the driven member is brought in contact with the driving member, it also starts rotating. When the driven member is separated from the driving member, it stops revolving. In this way a clutch operates.