KEVOS® MAKEOS · Power Transmission
Band Brake Stopping Design
Can this band brake stop the load in the time required, what lever force does it need, and how hot does it get?
Design of a simple band brake to stop a rotating inertia: braking torque to stop in the target time against a load that resists or overhauls (as in hoist lowering), design torque with a service factor, band tensions from the Euler relation, lever force and lining pressure, actual stopping time and angle, energy per stop, drum temperature rise and average heat.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Duty | ||
| Inertia at the brake drum | kg·m² | Inertia of everything being stopped, referred to the drum shaft. |
| Speed at the start of braking | rpm | Drum speed when braking starts. |
| Required stopping time | s | Time within which it must stop. |
| Load torque | N·m | Torque from the load (friction or gravity). |
| Load torque | choice | Whether the load torque resists rotation or drives it (overhauling loads make stopping harder). |
| Service factor | Factor on torque for lining variation. | |
| Brake | ||
| Drum diameter | mm | Brake drum diameter. |
| Wrap angle | ° | Angle of drum covered by the band. |
| Friction coefficient | Lining friction coefficient. | |
| Lever length to the applied force | mm | Lever arm from the fulcrum to the applied force. |
| Lever length to the band slack end | mm | Lever arm from the fulcrum to the band’s slack end. |
| Band width | mm | Width of the band. |
| Lever force available | N | Force the operator, spring or actuator can apply at the lever (about 250–300 N for a hand lever). |
| Allowable lining pressure | MPa | Allowable pressure for the lining material. |
| Heat | ||
| Drum mass absorbing heat | kg | Mass of the drum that soaks up the heat. |
| Drum specific heat | J/kg·K | Specific heat of the drum (460 J/kg·K for steel). |
| Stops per hour | How often the brake stops the load. | |
Method and formulas
- Torque to stop in time T = J ω ÷ t ± load torque (+ when overhauling); design torque = SF × T.
- Band brake: net pull = T ÷ r; slack tension T₂ = net ÷ (e^(μθ) − 1); tight T₁ = T₂ + net; lever force = T₂ b ÷ a; peak pressure = T₁ ÷ (r w) (handbook band brake formulas).
- Actual stopping time = J ω ÷ (T_design ∓ T_L); angle = ω t ÷ 2.
- Energy = ½ J ω² ± T_L × angle; temperature rise = energy ÷ m c_p.
- Example: stopping 5 kg·m² from 600 rpm in 2 s needs 258.85 N·m and 41.6 N on the lever.
Limitations
- Anchored end is the tight side for the rotation shown; reverse rotation needs much more lever force.
- Constant friction; fade at high temperature is not modelled.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Size a band brake for a winch, hoist or flywheel
- Check stopping time and heating at a new duty
- Find the lever force an operator or actuator must apply
Who it is for
- Design engineers
- Maintenance engineers
- Power transmission engineers
What you get
- Braking torque and design torque
- Band tensions, lever force and lining pressure
- Stopping time, energy and heat
Interpreting the result
- For hoists, size for the overhauling case with the heaviest load lowering at full speed.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 2455–2458. Topic reference; no source tables or recommended settings are reproduced.
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