Power developed at at the output shaft is known as brake power. Brake power is calculated as difference between indicated power (Power produced in cylinder) and power lost due to friction. As this power is calculated by applying brakes hence known as brake power.
Friction power= indicated power- brake power
W= net load acting on the brake drum in Kg
R= radius of brake drum in m
N= revolutions per minute of the crankshaft
T= torque applied due to the net load W on the brake drum in N-m
Brake power= W* R in kg-m
9.81* W* R in N-m