The name has been applied generally to all kinds of instruments used in the measurement of a force, as for example electric dynamometers, but the term specially denotes apparatus used in connection with the measurement of work, or in the measurement of the horse-power of engines and motors.
Dynamometers can be broadly classified into two major types,
1) Absorption dynamometers - In this type, work done is converted into the heat by friction while being measured. Viz. Prony brake dynamometer, rope brake dynamometer
2) Transmission dynamometers - In this type, the work is not absorbed in process, but it is utilized after the measurement. For example: - belt transmission and torsion dynamometer.
While A brake is an appliance used to apply frictional resistance 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 atom measure the frictional resistance. This is used to determine the power developed by the machine while maintaining its speed at rated value.
Types of brake and dynamometer
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
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.
Rope Brake Dynamometer:-
It consists of a number of turns of rope wound around the rotating drum attached to the output shaft. One side of the rope is connected to a spring balance and the other side to a loading device. The power is absorbed in friction between the rope and the drum. Therefore drum in rope brake requires cooling.
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 shoes is little less than the internal diameter of the drum. It is having at least one self energizing shoe per wheel. This results in tremendous friction.
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.