# 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 Linear velocity of load (v), ft/sec
g = Gravitational acceleration constant  Change in potential energy (PE), ft-lb
Weight of overhauling load (W), lb
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
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 