KEVOS® MAKEOS · Power Transmission
Spring-Applied Holding Brake Sizing (Stop Time, Energy and Holding)
Will this spring-applied brake stop and hold the load in time, and can it absorb the stopping energy at this number of stops per hour?
Check of a spring-applied (fail-safe) motor brake: kinetic energy of the inertia at the motor shaft, the net decelerating torque with the load either driving through the stop (lowering, overhauling) or helping it, slip time and total stop time with the engagement delay, stopping angle, friction energy per stop and per hour against the brake’s permissible values, the brake torque needed for the required stop time, and the holding factor on the static load torque.
Open the calculatorRuns in your browser. No account needed.
How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Speed at the brake | rpm | Speed of the brake shaft when braking starts (usually motor speed). |
| Total inertia at the brake shaft | kg·m² | Motor, brake and load inertia referred to the brake shaft. |
| Load torque at the brake shaft | N·m | Static load torque at the brake shaft (for a hoist, the load torque through the gearing). |
| Load during the stop | choice | Whether the load keeps driving during the stop (overhauling) or helps to stop it. |
| Brake torque (dynamic rating) | N·m | Dynamic braking torque of the brake (from the maker). |
| Engagement delay | s | Time from switching off until the brake torque builds up. |
| Required total stop time | s | Longest acceptable time from signal to standstill. |
| Holding factor required | Ratio of brake torque to static load torque you require for holding. | |
| Permissible energy per stop | kJ | Largest friction energy per stop for the brake (from the maker). |
| Stops per hour | Number of stops per hour. | |
| Permissible energy per hour | kJ | Largest friction energy per hour for the brake (from the maker). |
Method and formulas
- ω = 2π n ÷ 60; net torque = T_b − T_L (overhauling) or T_b + T_L (assisting).
- Slip time t_b = J ω ÷ T_net; total stop time = t_d + t_b; stopping angle = ω t_d + ω t_b ÷ 2.
- Friction energy per stop W = T_b ω t_b ÷ 2 (= J ω² ÷ 2 × T_b ÷ T_net); per hour = W × stops.
- Torque for the required stop time = J ω ÷ (t_req − t_d) ± T_L; holding factor = T_b ÷ T_L.
- Example: 60 N·m stops 0.05 kg·m² from 1450 rpm in 0.2398 s, absorbing 0.86462 kJ per stop.
Limitations
- Constant brake torque; the dynamic torque falls as the lining heats and wears.
- Speed is taken as constant during the engagement delay; an overhauling load speeds up a little.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Choose a motor brake for a hoist, conveyor or axis
- Check a brake for more stops per hour
- Estimate how far a load travels after an emergency stop
Who it is for
- Design engineers
- Maintenance engineers
- Power transmission engineers
What you get
- Net decelerating torque and stop time
- Stopping angle
- Energy per stop and per hour, torque for the required time and holding check
Interpreting the result
- For hoists the overhauling case governs: the net torque is the brake torque less the load torque.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 2455–2459. 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.
Open the Spring-Applied Holding Brake Sizing (Stop Time, Energy and Holding) calculator
