Clutch

Clutch is located in between engine and gear box and purpose of clutch is act as a linkage between engine and gear box. 
Clutch is use for engage and disengage of gear box from engine. 
When we engage the clutch, the pressure plate squeeze with flywheel and rotate at the same speed of flywheel. The engage and disengage mechanism is done with the help of diaphragm spring.

Why we need clutch ? 
Ans. In car we need clutch because the engine spins all the time, but the car's wheels do not. in order for car to stop without killing the engine. The wheel need to be disconnected from engine somehow. The clutch allows us to smoothly engage a spinning engine to a non spinning transmission.


How clutch is working ?
Ans.When the clutch pedal is pressed, a cable or hydraulic piston pushes on the release fork, which presses the throw-out bearing 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. 

 If clutch won't release properly, it will continue to turn the input shaft. This can cause grinding, or completely prevent car from going into gear. Some common reasons a clutch may stick are:

·         Broken or stretched clutch cable - The cable needs the right amount of tension to push and pull effectively.

·         Leaky or defective slave and/or master clutch cylinders - Leaks keep the cylinders from building the necessary amount of pressure.

·         Air in the hydraulic line - Air affects the hydraulics by taking up space the fluid needs to build pressure.

·         Misadjusted linkage - When your foot hits the pedal, the linkage transmits the wrong amount of force.

·         Mismatched clutch components - Not all aftermarket parts work with your clutch.

Types of clutch

Multiple plate clutch: It is used in race cars including F1, Indy Car, World Rally and even most club racing, motorcycles, automatic transmissions and in some diesel locomotives with mechanical transmissions. It is also used in some electronically controlled all-wheel drive systems as well as in some transfer cases.

Wet & dry

A wet clutch is immersed in a cooling lubricating fluid that also keeps surfaces clean and provides smoother performance and longer life. Wet clutches, however, tend to lose some energy to the liquid. Since the surfaces of a wet clutch can be slippery (as with a motorcycle clutch bathed in engine oil), stacking multiple clutch discs can compensate for the lower coefficient of friction and so eliminate slippage under power when fully engaged. A dry clutch, as the name implies, is not bathed in liquid and should be, literally, dry.

Centrifugal

This clutch system employs centrifugal force to automatically engage the clutch when the engine rpm rises above a threshold and to automatically disengage the clutch when the engine rpm falls low enough. 

Cone clutch

 The best known example of a cone clutch is a synchronizer ring in a manual transmission. The synchronizer ring is responsible for "synchronizing" the speeds of the shift hub and the gear wheel to ensure a smooth gear change.

Other type of clutch

Belt clutch:  Engine power is transmitted via a set of vee-belts that are slack when the engine is idling, but by means of a tensioner pulley can be tightened to increase friction between the belts and the sheaves.

Dog clutch: Utilized in automobile manual transmissions.

Hydraulic clutch: The driving and driven members are not in physical contact; coupling is hydrodynamic.

Electromagnetic clutch are, typically, engaged by an electromagnet that is an integral part of the clutch assembly.

Calculation of gear-box

What is a gear box?

Ans. Gear box is a combination of shaft, gears, dog clutch, intermediate shaft, counter shaft, drive shaft etc. The main purpose of a gear box is to vary torque and range of speed requires at different conditions.
     

         Let 

                                N₁ = No of teeth of the driving gear.

                                N₂= No of teeth of the driven gear.

                                Gear ratio (R) =N2/N1

If P= Power develop by the engine

T= Toque produce by engine

ω = angular velocity.

P= T*ω

If N₁ < N₂

Power is constant for both the gear

T₁*ω ₁ =T₂*ω ₂  …………….(1)                                       ω=(2*pi*n)/60

                                                                                            n = rpm

Since N₁ < N₂

ω ₁> ω ₂

Therefore from eqn. (1)

T₁<T₂

T is directly proportional to N

R=(ω _1/ω _2)=(N2/N1)

But maximum speed of the vehicle doesn't depend upon the gear ratio of the drive line. It depends on the power of engine that can push the vehicle to overcome all the resistant.

Let a 10 hp engine vehicle have drive line efficiency 80%. Therefore power available at wheel is 8 hp.

Aero dynamic drag+ rolling resistant + gradient resistant= 8 hp ……………..(2)

Aerodynamic drag=.5*c* v³

Rolling drag= F_r*v

Gradient resistant= F_g*v

Where c = coefficient of drag.

v= velocity of the vehicle.

The velocity calculate from the eqn. (2) is the maximum velocity that the vehicle can push by the engine.

Drive-train/Transmission of vehicle

What is Drive train or Transmission line of a vehicle?
Ans.  The drive line of a car includes the flywheel, clutch, drive shaft, gear box, differential  and axle shaft along with necessary universal joints. Drive line transmits power from engine to wheel through all these parts.

      When drive line transmits power from engine to Front Wheel it is called Front Wheel Drive, when power delivers to Rear wheel it is called Rear Wheel drive and in some vehicle power is delivers to all the four wheel it is called All Wheel drive or Four Wheel Drive.
      
What is Drive train efficiency?
Ans. The power develop by the engine is delivers to wheel through drive line. But practically it is observed that the power available at wheel is less than that of power develop by the engine. There is loss of power in the drive line. The loss is mainly due to the inertia of all rotating part like flywheel, clutch, drive shaft, gears etc. Some amount of torque needed to rotate all these part and the loss is more  when no. of rotating parts and mass of the rotating part is more.