Rope Brake Dynamometer:

Rope Brake Dynamometer:

The rope brake as shown in below figure is another device for measuring brake power of an engine. It consists of some 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.Rope brake dynamometers are cheap and can be constructed quickly but brake power can’t be measured accurately because of change in the friction coefficient of the rope with a change in temperature.

The brake power is given by the formula

Brake Power (bp) = π DN (W − S)

where D is the brake drum diameter,
W is the weight of the load and
S is the spring balance reading.