EXPERIMENT No. 8

EXPERIMENT No. 8
8.0 Observations:                                            

Name of component
Function of component
1
Fixed brake plate
To carry the friction lining
2
Fulcrum
To fix the brake plate.
3
Brake shoe
To push outward against the rim of the drum and to reduce the speed of drum.
4
Friction lining
To increase the coefficient of friction and to prevent wearing away of the metal.
5
Revolving cam
Rotation of cam causes to push the shoes  against the rim of the drum.
6
Spring
To held on the shoes normally in Off position.
7
Brake drum
To enclose the entire mechanism to keep out dust and moisture.
9.0 Student related activity :
            The disc brake consists of rotating disc and two friction pads which are actuated by four hydraulic pistons  contained in two halves of an assembly called calliper. The calliper assembly is secured to the steering knuckle in a front wheel brake and to the axle housing in a rear wheel brake. The friction pads ride freely on each side of the disc. They are held in position by machined surface inside the calliper casting  & spring behind the hydraulic pistons. To apply the brake the hydraulic pressure is applied to the fluid inlet tube, due to which , wheel cylinder pistons force the friction pads against the rotating discs. In the released position , the springs hold the piston pads so that they maintain contact with the disc surface. The chief advantage of disc brakes is their resistance to fading, since the disc remains cool under repeated severe brake applications. Also pad wear adjustment  is automatic, renewal of the pad is quick & easy. The condition of the pad wear can be checked without dismantling the brake system.            Because these brakes are not self energising  more force is required to apply them.
10.0 Questions for confirmation of learning : 1. State the function of a brake- brake is a device by means of which artificial frictional resistance is applied to a moving machine member, in order to retard or stop the motion of a machine.
2. Fixed brake plate, fulcrum, brake shoes, friction lining, revolving cam, spring, brake drum.
3. When the brake pedal is pressed the brake shoes expand or move outwards and get pressed against the inner surface of the brake drum. The force of friction applied to the rotating drum produces a brake torque in the opposite direction, which retards or stops the rotating wheel.
11.0 Conclusion :
  16. heat energy             17. magnified                      18. shoe linin
19. A brake is a device used to exert considerable resistance over a moving body to stop or retard it within a short time period. In braking action the kinetic energy of moving body is absorbed. In a two wheeler, mechanically operated brake is commonly used to brake the motion of the wheel.
12.0 Questions:
1. Hydraulic brake cannot bring the member to rest and are mostly used where large amount of are to be transformed while the brake is retarding the load such as in lab. dynamometers, high way trucks and electric locomotives. Oil or some other medium is used to operate the brakes. Mechanical brakes operation and maintenance is easy and by simple mechanisms the brakes are applied.
2. While fitting the brake lining to the brake shoe heating and pressing processes are used.
3. Leather will easily wear out and burn. Due to this frequent maintenance and repair will require.
4. The friction lining comes in contact with the drum. This causes friction. This friction in turn will heat the brake drum
5. Certain changes in the construction and assemblage of the wheels are required prior to applying internal expanding brakes to bicycle.
6. The major functional difference between a clutch and a brake is that clutch is used to keep the driving and driven member moving together, whereas brakes are used to stop a moving member or to control it’s speed.
7. The capacity of brake depends upon –
            a) The unit pressure between the braking surfaces
            b) The co-efficient of friction between the braking surfaces
8. a) It should have high co-efficient of friction with minimum fading. i.e. the co-efficient of friction should remain constant with change in temperature.
b) It should have low wear rate.
c) It should have high heat resistant
d) It should have high heat dissipation capacity.
e) It should have adequate mechanical strength.
9. Bronze on C.I., fiber on metal, steel on C.I. cork on metal, wire asbestos on metal.
10. Internal expanding brake is robust powerful, and efficient braking system than band brake.

11. In braking arrangement the shoes are normally held in off position by a spring, otherwise the shoes will come in contact with the brake drum and lining will be always in contact with drum.  

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