An electric wire-rope hoist combines a motor, reduction gearing, rope drum and holding brake to raise or lower a suspended load. Enter motor and drum speed, load mass and effective winding diameter to compare reduction ratios, line speed, drum torque and ideal lifting power. The animated rope travel follows the drum rotation.
Electric Hoist Interactive Calculator
Compare motor-to-drum ratios and load weight. Add effective winding diameter to calculate single-line speed, static drum torque and ideal lifting power.
Equation Used
- One supporting rope and constant effective winding diameter.
- Quasi-static suspended weight with g=9.80665 m/s².
- Lossless power comparison; no motor or component selection.
- Animation uses the higher drum speed at half physical speed and endpoint holds.
Ideal single-part rope model. No component capacity, brake rating or structural calculation.
Motor rotation becomes rope travel
The motor drives the drum through enclosed reduction gearing. Rope winding onto the drum raises the hook; unwinding lowers it. A brake holds the drive when commanded motion stops. The animation identifies the motor, enclosed reduction gearbox, drum and brake.
The illustration shows a single supporting rope and a constant effective winding diameter. An actual hoist may have several supporting rope parts, guides, return sheaves and a different physical arrangement. Demag’s rope-hoist documentation provides examples of these components and their integration.
In this model, rising distance h and drum angle θ obey h=(D/2)θ in magnitude. The hook moves through an illustrative 0.75 m range. Endpoint pauses make reversal visible; neither acceleration nor brake engagement dynamics is calculated.
Compare required drive ratios
Enter suspended mass, motor speed, two alternative drum speeds and effective rope winding diameter. The two drum entries are sorted into slower and faster operating points, even if their input order is reversed.
Required reduction ratio is motor rpm divided by drum rpm. These are two calculated alternatives at one specified motor speed. The calculator does not establish that an existing fixed-ratio gearbox can produce both, or determine a pole-changing or variable-speed motor configuration.
Winding diameter is measured to the effective rope centreline. Extra rope layers would change that diameter and therefore speed and torque; the present model keeps it constant.
Weight, torque, speed and ideal power
Suspended weight is F=mg, with g=9.80665 m/s². For one supporting rope, the ideal static line tension is F. Drum torque is T=FD/2 with diameter D in metres.
Line speed is πDn metres per minute when n is drum rpm. Dividing by 60 gives metres per second. Ideal upward mechanical power is P=FπDn/60 watts; divide by 1000 for kilowatts.
The reduction ratios are nmotor/nfast and nmotor/nslow. They describe speed reduction only. Losses, motor torque capability, starting current and acceleration are not inferred from the ratio.
Default operating points
For 1,500 kg, weight is 14.710 kN. With a 400 mm effective winding diameter, static drum torque is approximately 2,942.0 N·m.
At 1,400 motor rpm, a 5 rpm drum requires a 280:1 speed ratio, while 30 rpm requires approximately 46.67:1. The corresponding single-rope line speeds are approximately 6.28 and 37.70 m/min.
The faster point requires approximately 9.24 kW of ideal upward mechanical power before losses. This is not a motor nameplate recommendation. Doubling mass doubles weight, torque and power; doubling winding diameter doubles torque, line speed and power at fixed rpm.
Limits of the lifting calculation
This is a quasi-static comparison with one supporting rope, constant winding diameter and no drivetrain losses. It does not calculate rope strength, hook or sling capacity, brake torque rating, structural stresses, duty classification, acceleration or thermal limits.
A real multi-part reeving system changes hook speed and individual line tension. Use its actual geometry rather than applying these single-part results unchanged. Extra layers on a winding drum also require a variable-radius model.
Service limits, maintenance dimensions and component ratings depend on the specific hoist and its manufacturer documentation. The entered mass is a calculation input, not an approved load for the depicted equipment.
Electric hoist questions
Why does the drum reverse when the load descends?
The drum winds in rope to raise the load and pays it out to lower the load, so reversal changes the direction of travel.
Why is winding diameter needed?
Rpm alone is insufficient to determine rope speed or required drum torque. Winding diameter supplies the missing radius.
Does the animation run at real speed?
Motion is shown at half the calculated line speed, with short holds at the endpoints. The numerical speeds are the physical ideal values.
Does the calculated power select a motor?
No. It is ideal lifting power before losses, acceleration, duty and control requirements.
Are the two ratios one selectable gearbox?
No. They are two required ratios for the entered speed points. Gearbox architecture is not synthesized.
References
- Demag DHR rope hoist — rope drum, guide, motor, gearbox and hoist brake as distinct working assemblies.
- Demag DH hoist units — examples of integrated drum gearing and brake arrangements. The calculator is a generic ideal model and does not reproduce or rate a Demag product.
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