16-10-2012, 11:27 AM
BRAKES AND DYNAMOMETER
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ABSTRACT:-
The main objective of writing this term paper is to present the theoretical concept of brakes and dynamometer. A brake is an appliance used to apply frictional resistance to the frictional body whereas the dynamometer is a brake incorporating device to measure the frictional resistance applied.
There are different types of brake they are different in construction as well as having different efficiency according to its efficiency we used these brake in different places. These are classified into block brake, band brake, and band and block brake, internal expanding shoe brake.
A dynamometer is also divided into two parts that are absorption and transmission dynamometer. We use as per the frictional resistance required.
INTRODUCTION:-
A brake is an appliance used to applyfrictionalresistance to a moving body to stop or retard it by absorbing its kinetic energy. In general every motion, there is always some amount of resistance which retards the motion and brings the body in rest.
A dynamometer is a brake incorporating ato measure the frictional resistance. This is used to determine the power developed by the machine while maintaining its speed at rated value.
BLOCK OR SHOE BRAKE:-
It consists of a block or shoe which is pressed against a rotating drum the force on a drum can be increased by using a lever. We can also use two blocks on either sides of a drum and this also doubles the torque.
BAND BRAKE:-
It consists of a rope, belt or flexible steel band (lined friction material which is pressed against the external surface of a cylindrical drum when the brake is applied).The force is applied at the free end of the lever.
BAND AND BLOCK BRAKE:-
It consists of a no. of wooden block secured inside a flexible steel band. When the brakes is applied the block are passed against the drum the two sides of the band becomes tight and slacks as usual. Wooden blocks have high coefficient of friction; thus, increase the effectiveness of the brake.
INTERNAL EXPANDING SHOE BRAKE:-
It consists of two semi-circular shoes which are lined with friction material such as ferodo. The shoes press against the inner flange of the drum when the brakes are applied. Under normal running of the vehicle, the drum rotates freely as the outer diameter of the shoesis little less than the internal diameter of the drum.
It is having at least one self energising shoe per wheel. This results in tremendous friction.
TYPES OF DYNAMOMETER:-
1. Absorption dynamometer:-
In this type, work done is converted into the heat by friction while being measured. Viz. Prony brakedynamometer, rope brake dynamometer
2. Transmission dynamometer:-
In this type, the work is not absorbed in process, but it is utilised after the measurement. For example:- belt transmission and torsion dynamometer.
PRONY BRAKE DYNAMOMETER:-
It consists of two wooden blocks damped together in a revolving pulley carrying a lever. The friction between block and the pulley tends to rotate the blocks in the direction of rotation of the shaft. The grip of the blocks over the pulley is adjusted using the bolts and clamps until the engine runs at required speed.
TORSION DYNAMOMETER:-
It is consists of two discs A and B , a lamp and the movable torque finder is attached to it.
The two discs are similar and fixed to the shaft at fixed distance from each other. Thus the two discs revolve with the shaft. The torque finder has an eye piece capable of moving circumferentially. When the shaft rotates freely all 4 slots are in the line and a ray can easily be seen by eyepiece. After every revolution when torque is transmitted, the shaft twists and the slots in the disc b shifts its position. The eyepiece is moved by a micrometre spindle.
CONCLUSION:-
By going through all the theoretical aspects of brake and dynamometer we can easily understand the working and construction of all the different types of brake and dynamometer. Following main points are comes into consideration –
1. A brake is an appliance used to apply frictional resistance to moving body to stop or retard it by absorbing its kinetic energy.
2. There are 4 main type of brakes.
3. A block or shoe brake consist of a block or shoe which is pressed against the rotating drum.
4. A band brake is consists of a rope, belt or flexible steel band.
5. A band and block brake consists of a number of wooden block secured inside a flexible steel.
6. An internal expending shoe brake consists of two semi-circular shoes which are lined with frictional material such as ferodo.
7. There are 2 types of dynamometer.