KEVOS® MAKEOS · Power Transmission
Bearing and Gear Losses with Circulating Oil Flow
How much heat do these bearings and gears make, and how much circulating oil carries it away?
Heat from rolling bearings by the friction-coefficient method (torque = μ P d ÷ 2, as the bearing friction tool) plus other losses such as gear mesh or seals, and the circulating oil flow to carry that heat away at an allowed oil temperature rise (as the coolant heat-flow tool with oil properties).
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Number of bearings | Number of bearings on the circuit. | |
| Equivalent load per bearing | N | Equivalent load on each bearing. |
| Bearing bore | mm | Bore diameter of the bearings. |
| Bearing friction coefficient | Friction coefficient referred to the bore (about 0.001 cylindrical roller, 0.0015 deep groove ball, 0.002 tapered and spherical roller). | |
| Speed | rpm | Shaft speed. |
| Other losses (gear mesh, seals, churning) | W | Other heat going into the oil. |
| Allowed oil temperature rise | K | Temperature rise of the oil through the machine. |
| Oil specific heat | kJ/kg·K | Specific heat of the oil. |
| Oil density | kg/m³ | Oil density. |
Method and formulas
- Friction torque per bearing M = 0.5 μ P d.
- Bearing loss = M ω × number of bearings; total heat = bearings + other losses.
- Oil flow Q = heat ÷ (ρ c_p ΔT).
- Example: the bearings lose 58.905 W; with other losses the oil needs 0.93976 L/min at a 10 K rise.
Limitations
- Constant friction coefficient; at high speed and light load, lubricant churning dominates.
- Oil flow for heat only; bearings also need a minimum flow for lubrication.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Size a circulating oil system for a gearbox or spindle
- Estimate bearing heat for a thermal check
- Check whether splash lubrication is enough
Who it is for
- Design engineers
- Maintenance engineers
- Power transmission engineers
What you get
- Bearing friction torque and power loss
- Total heat
- Oil flow required
Interpreting the result
- If the flow is very low, splash or grease lubrication may carry the heat without a circulating system.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 2365–2440. Topic reference; no source tables or recommended settings are reproduced.
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