Identify input rpm
Use the shaft speed at the actual operating frequency and load, rather than assuming synchronous motor speed.
HOISTING & TRAVEL / TOOL 19
Gear Ratio & Travel Speed Calculator
Translate a motor and gearbox proposal into wheel travel speed or drum rope speed.
Before you start: required inputs
- Read the operating motor shaft speed and the total reduction ratio from the drive data.
- Use the effective rolling diameter for a wheel, or the rope centre-line winding diameter for a drum.
Calculation diagram
A PRACTICAL WALKTHROUGH
How to use this calculator
Combine reductions
Multiply the stage ratios to obtain the total input-to-output reduction ratio.
Read the line speed
Check the output rpm and linear speed. For a reeved hoist, convert drum rope speed into hook speed separately.
1,450 rpm through a 50:1 gearbox
THE INPUTS
1,450 rpm input, 50:1 total reduction and a 315 mm effective diameter.
THE RESULT
The output turns at 29 rpm and produces about 28.698 m/min of wheel or rope line speed.
What does the result mean?
01
A larger effective diameter increases linear speed at the same output rpm.
02
The result assumes no slip and constant diameter.
03
The calculator does not determine transmitted torque, gearbox rating or motor power.
Watch for this
Using the bare drum diameter even though the rope centre-line diameter is larger and changes with winding layer.
Formula & model conditions +
n_out = n_motor / i
v = π D n_out
- No slip and constant effective diameter.
- For a drum the result is rope speed; divide by the supporting rope count to obtain ideal hook speed. Motor speed must be the actual operating speed.
Common questions
Is drum rope speed equal to hook speed?
Only for a suitable single-part arrangement. With multiple supporting rope parts, ideal hook speed is lower and follows the reeving geometry.
Can I use the motor nameplate rpm?
Use it when it represents the assessed operating condition. A variable-frequency drive may run the motor at another speed.