Formulas 

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

REQUIRED GIVEN FORMULA
Full load motor torque formula-1_1.JPG
Horsepower (P), hp
Shaft speed (N), rpm
5252 = Constant
Formula-1.JPG
Average dynamic braking torque formula-2.JPG
Total inertia reflected to brake  formula-2_2.JPG
Shaft speed at brake (N), rpm
Desired stopping time (t), seconds
308 = Constant
formula-2_3.JPG
Static torque (T), lb-ft
Force (F), lb
Pulley or drum radius, (R), ft
formula-3.JPG
Overhauling dynamic torque reflected to brake shaft  formula-4-(1).JPG
Weight of overhauling load (W), lb
Linear velocity of descending load (V), ft/min
Shaft speed at brake (N), rpm
0.158 = Constant
formula-4_4.JPG
Static torque of brake formula-5.JPG
Dynamic braking torque required formula-5_2.JPG
0.8 = Constant (derating factor)
formula-5_3.JPG
Inertia of rotating load reflected to
brake shaft  formula-6-(1).JPG
Inertia of rotating load formula-6_2-(1).JPG
Shaft speed at load formula-6_3.JPG
Shaft speed at brake formula-6_4-(2).JPG
formula-6_5.JPG
Equivalent inertia of linear moving load
reflected to brake shaft formula-7-(1).JPG
Weight of linear moving load (W), lb
Linear velocity of load (V), ft/min
Shaft speed at brake formula-8-(1).JPG
2 = Constant
formula-9.JPG
Kinetic energy of rotating load, formula-10.JPG
Inertia of rotating load reflected to brake shaft
formula-11.JPG 
Shaft speed at brake formula-11_3-(2).JPG
5875 = Constant
formula-11_2-(1).JPG
Kinetic energy of linear moving load formula-12-(2).JPG
Weight of load (W), lb
Linear velocity of load (v), ft/sec
g = Gravitational acceleration constant formula-12_2.JPG
formula-12_3.JPG
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 formula-13.JPG
Total linear kinetic energy formula-14_3.JPG
Total rotary kinetic energy formula-14_4.JPG
Potential energy converted to kinetic energy
(PE), ft-lb
formula-14.JPG
Thermal capacity required for rotational or linear
moving loads (TC), hp-sec/min
Total system inertia reflected to brake shaft 
formula-15_2.JPG
Shaft speed at brake formula-15_3.JPG
Number of stops per minute (n), not less
than one formula-15_4.JPG
Formula-15_5-(1).JPG
Thermal capacity required for overhauling loads
(TC), hp-sec/min
Total energy brake absorbs formula-16-(2).JPG
Number of stops per minute (n), not less
than one 550 = Constant
formula-16_2.JPG
Linear velocity, ft/min
N = rpm
Diameter (D), ft
formula-17.JPG