# Formulas

### The following formulas cover the basic calculations used in brake application engineering.

REQUIRED GIVEN FORMULA
Full load motor torque
Horsepower (P), hp
Shaft speed (N), rpm
5252 = Constant
Average dynamic braking torque
Total inertia reflected to brake
Shaft speed at brake (N), rpm
Desired stopping time (t), seconds
308 = Constant
Static torque (T), lb-ft
Force (F), lb
Pulley or drum radius, (R), ft
Overhauling dynamic torque reflected to brake shaft
Weight of overhauling load (W), lb
Linear velocity of descending load (V), ft/min
Shaft speed at brake (N), rpm
0.158 = Constant
Static torque of brake
Dynamic braking torque required
0.8 = Constant (derating factor)
Inertia of rotating load reflected to
brake shaft
Inertia of rotating load
Shaft speed at load
Shaft speed at brake
Equivalent inertia of linear moving load
reflected to brake shaft
Weight of linear moving load (W), lb
Linear velocity of load (V), ft/min
Shaft speed at brake
2 = Constant
Kinetic energy of rotating load,
Inertia of rotating load reflected to brake shaft

Shaft speed at brake
5875 = Constant
Kinetic energy of linear moving load
Weight of load (W), lb
Linear velocity of load (v), ft/sec
g = Gravitational acceleration constant
Change in potential energy (PE), ft-lb
Weight of overhauling load (W), lb
Distance load travels (s), ft
PE = Ws
Total energy absorbed by brake
Total linear kinetic energy
Total rotary kinetic energy
Potential energy converted to kinetic energy
(PE), ft-lb
Thermal capacity required for rotational or linear
moving loads (TC), hp-sec/min
Total system inertia reflected to brake shaft
Shaft speed at brake
Number of stops per minute (n), not less
than one
Thermal capacity required for overhauling loads
(TC), hp-sec/min
Total energy brake absorbs
Number of stops per minute (n), not less
than one 550 = Constant
Linear velocity, ft/min
N = rpm
Diameter (D), ft