KEVOS® MAKEOS · Mechanics
Brake Dynamometer Test and Cooling Plan (Power, Water Flow, Water Use)
How much power is my prony brake or absorption dynamometer taking, how much cooling water does it need for the temperature rise I allow, and do my brake rating and water supply cover it?
Plan for a power test with a prony brake or absorption dynamometer: net scale force, torque and power absorbed from the arm length, scale readings and speed (as the prony brake tool), the share of the power carried away by the cooling water, the water flow for your allowed temperature rise (as the coolant flow for a heat load tool), the water used over the test, and checks against the brake rating and the water supply.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Brake arm length | m | Distance from the shaft centre to the scale load point. |
| Scale reading with the brake absorbing power | N | Scale reading while the brake absorbs power. |
| Zero reading (frictionless) | N | Scale reading with the brake slack (the arm’s own weight). |
| Shaft speed | rpm | Shaft speed during the reading. |
| Cooling | ||
| Share of the power removed by the water | % | Share of the absorbed power taken away by the cooling water (the rest goes to air and the structure). |
| Allowed water temperature rise | K | Largest rise in water temperature through the brake. |
| Water specific heat | kJ/(kg·K) | Specific heat of the water. |
| Water density | kg/m³ | Density of the water. |
| Test duration | min | Length of the test run. |
| Limits | ||
| Brake power rating | kW | Largest power the brake can absorb continuously. |
| Water supply available | L/min | Water flow the supply can give. |
Method and formulas
- Net force = reading − zero; torque = force × arm; power = 2π n T ÷ 60 (as the prony brake tool).
- Heat to water = power × share; flow = heat ÷ (ρ c_p ΔT) (as the coolant flow for a heat load tool).
- Water used = flow × test duration.
- Example: the brake absorbs 12.566 kW at 200 N·m; it needs 16.267 L/min of water and 488 L for the test.
Limitations
- Steady readings; scale damping is needed for a stable reading.
- Water share depends on the brake design; air-cooled brakes need a different heat path.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Plan an engine or motor power test
- Size the water supply for a water-cooled brake
- Check a dynamometer is big enough
Who it is for
- Test engineers
- Maintenance engineers
- Technical college staff
What you get
- Torque and power absorbed
- Cooling water flow and test water use
- Checks against rating and supply
Interpreting the result
- If the supply is short, allow a larger temperature rise within the brake maker’s limit or recirculate through a cooler.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 2998–2999, 371–374. Topic reference; no source tables or recommended settings are reproduced.
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Open the Brake Dynamometer Test and Cooling Plan (Power, Water Flow, Water Use) calculator
