Standard Calculations
| REQUIRED | GIVEN | FORMULA |
|---|---|---|
| Speed ratio (R) | Shaft speeds (rpm) | R = rpm(faster shaft speed) / rpm (slower shaft speed) |
| Pulley diameters (D & d) | R = D (larger pulley diameter) / d (smaller pulley diameter) | |
| Number of pulley grooves (N&n) | R = N (larger pulley groove no.) / n (smaller pulley groove no.) | |
| Horsepower (hp) | Torque (T) in in-lbs Shaft speed (rpm) |
hp = (T x rpm) / 63,025 |
| Design horsepower (Dhp) | Rated Horsepower (hp) Service factor (SF) |
Dhp = hp x SF |
| Power (kw) | Horsepower (hp) | kw = 7457 x hp |
| Torque (T) in in-lbs | Shaft horsepower Shaft speed (rpm) |
T = (63,025 x hp) / rpm |
| Torque (T) in N-mm | Torque (T) in in-lbs | T = 112.98 x T |
| Peak Torque (T) | Torque (T) Service factor (SF) |
T = T x SF |
| Effective tension (te) in pounds | Shaft horsepower (hp) Belt speed (BS) |
Te = (33,000 x hp) / BS |
| Effective tension (Te) in Newtons | Te = 2248 x Te | |
| Effective tension (Te) in pounds | Torque (T) in in-lbs Pulley pd in inches |
Te = (2 x T) / pd |
| Effective tension (Te) in Newtons | Torque (T) in N-mm Pulley pd in mm |
|
| Effective tension (Te) in Newtons | Effective tension (Te) in pounds | Te = 4.4484 x Te |
| Centrifugal tension loss (Tc) | Smaller pulley pd Smaller pulley rpm Tc constant Kc |
Tc = Kc x pd2 x rpm2 |
| Allowable working tension (Ta) | Te, Tc & SF | Ta = (Te + Tc) x SF |
| Service factor (SF) | Belt width Rated Ta for given belt width Calculated Te & Tc |
SF = Rated Ta / (Te + Tc) |
| Belt speed (BS) in fpm | Pulley pd in inches Pulley speed in rpm |
BS = 262 x pd x rpm |
| Belt speed (BS) in m/s | Pulley speed in mm Pulley speed in rpm |
BS = 0.000524 x pd x rpm |
| Belt length (BL) | Center distance (C) Pulley diameters (D & d) |
BL = (2 x C + (D - d)^2 + 1.57 x (D + d)) / (4 x C) |
| Arc of contact on smaller pulley (A/Cs) | Pulley diameters (D & d) Center distance (C) |
A/Cs = 180 - ((D - d) x 60) / C |
If TIM is less than 6, correct peak totque by value shown in table below.
Teeth in Mesh (TIM) calculations
Determine arc of contact on smaller pulley (A/Cs) using the formula in the above chart. Determine teeth in Mesh (TIM) using the formula below
TIM = (A/Cs * Smaller pulley groove no. (n)) / 360
Drop any fractional part and use only the whole number, as any tooth not fully engaged cannot be considered a working tooth.
| TM | Design Peak Torque Multiplication Factor |
|---|---|
| 5 | 1.2 |
| 4 | 1.5 |
| 3 | 3 2.0 |
| 2 | Suggest alternate drive |
| 1 | Suggest alternate drive |