KEVOS® MAKEOS · Power Transmission
Winch Drum Brake Check (Load Torque at the Brake, Stop Time, Holding Factor, Brake Energy)
For a geared winch or hoist with a brake on the motor shaft, can the brake hold and stop the descending load quickly enough, and how much heat does each stop put into it?
Check of the motor-shaft brake of a geared rope winch or hoist: the drum torque from the rope load, the load torque at the brake through the gear ratio with the gear efficiency helping the brake when lowering, the rope speed, the inertia at the brake including the load reflected through the drum and gears, then the stopping time, stop distance, holding factor and energy per stop and per hour (as the holding brake sizing tool, load overhauling), against your stop time and brake ratings.
Open the calculatorRuns in your browser. No account needed.
How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Rope load | kN | Load on the rope at the drum, including hook and rope. |
| Drum diameter (to rope centre) | mm | Drum diameter to the rope centre (use the outer layer for a multi-layer drum). |
| Gear ratio (motor ÷ drum) | Total reduction from the motor to the drum. | |
| Gear efficiency | % | Efficiency of the gearing. |
| Motor speed | rpm | Motor speed when lowering. |
| Motor, brake and coupling inertia | kg·m² | Inertia of the motor rotor, brake disc and coupling. |
| Brake | ||
| Brake torque (dynamic rating) | N·m | Dynamic torque rating of the brake. |
| Engagement delay | s | Time from switching off to the brake gripping. |
| Required total stop time | s | Longest acceptable stop time. |
| Holding factor required | Brake torque as a multiple of the load torque needed for holding. | |
| Permissible energy per stop | kJ | Energy the brake may absorb in one stop. |
| Stops per hour | Stops per hour. | |
| Permissible energy per hour | kJ | Energy the brake may absorb per hour. |
Method and formulas
- Drum torque = F D ÷ 2; load torque at the brake when lowering = drum torque ÷ i × η; rope speed = π D n ÷ (60 i).
- Inertia at the brake = J_m + m (D ÷ 2i)² with m = F ÷ g.
- Stop time, angle, energy and holding factor with the load driving through the stop (as the holding brake sizing tool); stop distance = brake shaft angle × D ÷ 2i.
- Example: 15.938 N·m at the brake; the load stops in 0.22145 s after dropping 77.284 mm.
Limitations
- Rigid rope and gearing; rope stretch adds to the stop distance and softens the shock.
- Single brake on the motor shaft; a second (load) brake changes the duty.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Check the brake on a hoist or winch
- Find the stop distance of a descending load
- Check a brake after a gearbox change
Who it is for
- Lifting engineers
- Maintenance engineers
- Machine designers
What you get
- Drum torque, load torque at the brake, rope speed
- Inertia, stop time and stop distance
- Holding factor and brake energy
Interpreting the result
- When lowering, gear losses help the brake; when the gearbox is efficient the brake must do more.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 2455–2459, 165–168. Topic reference; no source tables or recommended settings are reproduced.
WORKOS tools are screening and decision-support utilities. Verify important financial, engineering, safety, legal or operational decisions using appropriate professional standards and your organisation’s approved data.
