BIZOMAT 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). |
What each input means
Open an input to see what it is, its units, the worked example and the common mistakes, with a small diagram.
What this means: Load including hook block
- What it is
- Heaviest mass lifted: the rated load plus the hook block, slings and any lifting attachments.
- Units and format
- Enter a number in kg: kilograms. The form accepts 0.000001 kg to 1000000 kg. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 5000 kg as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Line pull, drum torque and motor power are proportional to it.
What this means: Lifting speed
- What it is
- Speed at which the hook and load rise, not the rope speed at the drum.
- Units and format
- Enter a number in m/min: metres per minute. The form accepts 0.000001 m/min to 200 m/min. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 8 m/min as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Motor power rises in proportion to lifting speed.
- Get it right
- Rope speed at the drum is this hook speed times the number of rope parts.
What this means: Parts of rope supporting the load
- What it is
- Number of rope falls supporting the hook block: the rope parts between the block and the drum or top sheaves.
- Units and format
- Enter a plain number with no unit. The form accepts 1 to 24. Use a whole number. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 4 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- More parts reduce the line pull but raise the rope and drum speeds.
What this means: Sheave efficiency (each)
- What it is
- Efficiency of each sheave the rope runs over, allowing for bearing friction and rope bending, from the sheave or crane maker.
- Units and format
- Enter a number in %: percent: the number is read as a percentage, so type 8 for 8 %. The form accepts 80% to 100%. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 98% as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
What this means: Drum pitch diameter
- What it is
- Diameter of the drum measured to the centre of the rope as it winds on.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 5000 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 400 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Drum torque rises in proportion; the drum turns more slowly.
- Get it right
- Pitch diameter to the rope centre, not the barrel diameter.
What this means: Rope diameter
- What it is
- Nominal diameter of the wire rope, used only for the drum-to-rope diameter ratio check.
- Units and format
- Enter a number in mm: millimetres. The form accepts 0.000001 mm to 100 mm. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 14 mm as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
What this means: Rope minimum breaking load
- What it is
- Minimum breaking load of the rope, from the rope maker’s certificate or catalogue.
- Units and format
- Enter a number in kN: kilonewtons (1 kN = 1000 N). The form accepts 0.000001 kN to 100000 kN. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 120 kN as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- The rope safety factor is proportional to it.
- Get it right
- Kilonewtons; if the certificate gives tonnes or kilograms-force, convert first.
What this means: Required rope safety factor
- What it is
- Minimum ratio of rope breaking load to line pull required by the applicable crane standard for the duty.
- Units and format
- Enter a plain number with no unit. The form accepts 2 to 15. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 5 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
What this means: Required D/d ratio
- What it is
- Smallest ratio of drum pitch diameter to rope diameter allowed by the applicable crane standard for the duty.
- Units and format
- Enter a plain number with no unit. The form accepts 5 to 60. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 20 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
What this means: Gearbox efficiency
- What it is
- Efficiency of the hoist gearbox between motor and drum, from the gearbox maker.
- Units and format
- Enter a number in %: percent: the number is read as a percentage, so type 8 for 8 %. The form accepts 30% to 100%. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 94% as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Motor power is inversely proportional to it.
What this means: Motor poles (50 Hz)
- What it is
- Number of poles of the induction motor, which sets its synchronous speed.
- Units and format
- Choose one of 4 options from the list: 2-pole; 4-pole; 6-pole; 8-pole.
- Example
- The form opens with “4-pole” selected as a worked example. Choose the option that matches your case.
- Get it right
- Synchronous speeds here assume a 50 Hz supply.
What this means: Motor slip
- What it is
- How far below synchronous speed the motor runs at full load, as a percentage, from the motor data sheet.
- Units and format
- Enter a number in %: percent: the number is read as a percentage, so type 8 for 8 %. The form accepts 0% to 15%. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 4% as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
What this means: Brake safety factor
- What it is
- Brake torque as a multiple of the load torque at the brake, as required by the crane standard or the brake design.
- Units and format
- Enter a plain number with no unit. The form accepts 1 to 4. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 1.75 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- Brake torque at the motor is proportional to it.
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