KEVOS® MAKEOS · Power Transmission
V-Belt Drive Motor Load Check (Belts, Driven Speed, Shaft Load on the Motor)
For a V-belt drive off an electric motor, how many belts does it need, does the driven speed come out right, and is the belt pull within the motor’s allowable shaft load?
Check of a V-belt or flat belt drive against its motor: the driven pulley size and speed, belt length, wrap, belt speed, effective pull, centrifugal tension, number of belts and the resultant shaft load from the tight and slack side tensions (as the V-belt drive design tool), against the grooves on the pulleys, the driven speed you need and the radial load the motor bearings are rated for at the pulley position.
Open the calculatorRuns in your browser. No account needed.
How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Power | kW | Power transmitted. |
| Motor speed | rpm | Motor speed. |
| Motor pulley pitch diameter | mm | Pitch diameter of the motor pulley. |
| Speed ratio (motor ÷ driven speed) | Motor speed divided by driven speed (driven pulley = ratio × motor pulley). | |
| Centre distance | mm | Distance between the shaft centres. |
| Service factor | Service factor for the driven machine and running hours. | |
| Belt | choice | V-belt in a 38° groove, or a flat belt. |
| Friction coefficient | Friction coefficient between belt and pulley. | |
| Belt mass per metre | kg/m | Mass of one belt per metre. |
| Allowable tension per belt | N | Largest working tension one belt may carry. |
| Motor and duty | ||
| Grooves on the pulleys | grooves | Number of grooves on the pulleys you have. |
| Motor allowable radial load at the pulley | N | Radial load the motor maker allows at the pulley’s position on the shaft. |
| Driven speed required | rpm | Speed the driven machine needs. |
| Speed tolerance | % | How far the driven speed may differ from the speed needed. |
Method and formulas
- Wrap θ = π − 2 asin ((D − d) ÷ 2C); belt speed; effective pull = P × SF ÷ v; centrifugal tension m v² (as the V-belt drive design tool).
- Belts = effective pull × e^{μθ} ÷ (e^{μθ} − 1) ÷ (allowable − centrifugal) rounded up; shaft load from T₁ and T₂ and the belt angle.
- Driven speed = motor speed ÷ ratio; compared with the speed needed.
- Example: 3 belts; the motor shaft carries 1,104.2 N and the driven pulley turns 580 rpm.
Limitations
- Steady load at the pulley position given by the motor maker; a pulley mounted further out lowers the allowable load.
- Belt capacity by allowable tension; the belt maker’s power ratings govern for a final selection.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Check a fan or pump belt drive on a standard motor
- Change pulleys without overloading motor bearings
- Find how many belts a drive needs
Who it is for
- Maintenance engineers
- Mechanical fitters
- HVAC engineers
What you get
- Driven pulley, speed and belt length
- Belts needed and shaft load
- Against the grooves, speed and motor rating
Interpreting the result
- A larger motor pulley lowers the belt pull and the shaft load for the same power; a small pulley is the usual cause of bearing failures.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 2487–2536. 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 V-Belt Drive Motor Load Check (Belts, Driven Speed, Shaft Load on the Motor) calculator
