KEVOS® MAKEOS · Power Transmission
Hoist Drive Sizing (Rope, Drum, Gearbox, Motor and Brake)
What rope pull, drum speed, gear ratio, motor and brake does this hoist need?
Sizing of an electric rope hoist: line pull at the drum for the reeving with sheave efficiency and the rope safety factor and D/d ratio (as the wire rope reeving tool), rope and drum speed, drum torque, gearbox ratio for the motor speed, motor power and the next standard rating, and the brake torque at the motor with a safety factor.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Load including hook block | kg | Mass lifted, including the hook block and rigging. |
| Lifting speed | m/min | Hook lifting speed. |
| Parts of rope supporting the load | Number of rope parts carrying the hook block. | |
| Sheave efficiency (each) | % | Efficiency of each sheave (about 98% with rolling bearings). |
| Drum pitch diameter | mm | Drum diameter to the rope centre. |
| Rope diameter | mm | Rope diameter. |
| Rope minimum breaking load | kN | Minimum breaking load of the rope. |
| Required rope safety factor | Rope safety factor required by the code for the duty. | |
| Required D/d ratio | Minimum drum-to-rope diameter ratio for the duty. | |
| Gearbox efficiency | % | Gearbox efficiency. |
| Motor poles (50 Hz) | choice | Motor pole count. |
| Motor slip | % | Motor slip at full load. |
| Brake safety factor | Brake torque as a multiple of the load torque at the brake (often 1.5–2). |
Method and formulas
- Line pull F = W (1 − η) ÷ (1 − ηⁿ) (W ÷ n when frictionless), as the reeving tool.
- Rope speed = lifting speed × n; drum speed = rope speed ÷ π D; drum torque = F D ÷ 2.
- Gear ratio = motor speed ÷ drum speed; motor power = F × rope speed ÷ η_gear, rounded up to the IEC series.
- Brake torque at the motor = factor × drum torque ÷ ratio.
- Example: 5000 kg at 8 m/min on 4 falls needs 12.632 kN line pull and a 7.5 kW motor.
Limitations
- Steady hoisting; acceleration, duty class and code factors must be added for the actual crane standard.
- Lifting equipment must be designed and certified to the applicable standard.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Size a hoist or winch drive
- Check a hoist for a heavier load or faster lift
- Specify the brake for a lifting drive
Who it is for
- Lifting equipment designers
- Maintenance engineers
- Machine designers
What you get
- Line pull, rope safety factor and D/d
- Drum speed and torque, gear ratio
- Motor power, rating and brake torque
Interpreting the result
- More parts of rope reduce line pull and motor torque but slow the hook and need more rope.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 2613–2625, 3444–3450. Topic reference; no source tables or recommended settings are reproduced.
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Open the Hoist Drive Sizing (Rope, Drum, Gearbox, Motor and Brake) calculator
