KEVOS® MAKEOS · Mechanics
Prony Brake and Absorption Dynamometer Power
How much power is the machine delivering according to the brake arm, scale reading and speed?
Torque and power absorbed by a Prony brake or water brake from the brake arm length, the scale reading under load, the zero reading and the shaft speed, with the heat that must be carried away.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Brake arm length | m | Horizontal distance from the shaft axis to the knife edge on the scale. |
| Scale reading with the brake absorbing power | N | Scale reading while the brake absorbs power. |
| Zero reading (frictionless) | N | Scale reading with friction removed (average of slow forward and backward readings). |
| Shaft speed | rpm | Speed of the braked pulley. |
Method and formulas
- Brake reading W = tare − zero reading.
- Torque = W L; power = 2π L n W ÷ 60 (the handbook’s H.P. = 2π L N W ÷ 33,000 in feet, rpm and pounds).
- All absorbed power becomes heat in the brake.
- Example: 200 N net on a 1 m arm at 600 rpm is 12.566 kW.
Limitations
- Steady running; readings fluctuate with friction changes.
- Water brakes need continuous water flow to remove the heat.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Measure the output power of a motor or engine on test
- Check a gearbox’s delivered torque
- Size cooling for a brake test rig
Who it is for
- Test engineers
- Maintenance engineers
- Engineering students
What you get
- Brake reading and torque
- Power absorbed
- Heat to remove
Interpreting the result
- Take readings at several loads to plot the machine’s torque and power curve.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 2998–2999. Topic reference; no source tables or recommended settings are reproduced.
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