How to use this on a job
Follow one motor revolution through the mechanics. A 30:1 reducer needs thirty input turns for one output turn. The roller then moves one circumference of belt for each output turn. That chain is the calculation.
- 01
Enter actual input shaft speed. A drive frequency alone does not determine actual induction-motor speed; slip and the motor design also matter.
- 02
Enter the ratio as input revolutions per output revolution. A reducer uses a number greater than one. A speed-increasing stage can use a ratio below one.
- 03
Enter the effective driving diameter, including any relevant covering. Read output RPM, metres per minute and metres per second. Compare predicted travel over a measured interval with the actual machine.
Work through one example
belt speed [m/min] = input rpm × π × diameter [mm] ÷ (ratio × 1000)
A 1,500 rpm input through a 30:1 reducer turns the roller at 50 rpm. A 100 mm roller has circumference about 314.159 mm, giving about 15.708 m/min. Doubling the diameter doubles belt speed at the same RPM; doubling the reduction ratio halves it.
Before you trust the answer
This is an ideal kinematic relationship with no belt slip. It does not size a motor, predict acceleration torque, or establish safe speed. Multiple stages multiply their input/output ratios. If an encoder is mounted elsewhere, calculate the travel at its own shaft rather than borrowing the motor’s ratio.