KEVOS® MAKEOS · Power Transmission
Overhung (Radial) Load on a Gearbox or Motor Shaft
What radial load does this pulley, sprocket or gear put on the gearbox shaft, and is it within the allowable at its position?
Overhung load check: shaft torque from power and speed, overhung load from the drive element’s pitch diameter and its tension factor (chain, gear, V-belt or flat belt), the catalogue allowable corrected for where the load actually sits on the shaft, and the resulting load on the outer bearing from the lever over the bearing span.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Power at the shaft | kW | Power transmitted through the shaft. |
| Shaft speed | rpm | Speed of the shaft. |
| Drive element | choice | Type of element on the shaft; the factor allows for belt or chain tension above the transmitted pull. |
| Pitch diameter of the element | mm | Pitch diameter of the sprocket, gear or pulley. |
| Catalogue allowable overhung load | kN | Allowable overhung load from the gearbox or motor catalogue. |
| Catalogue load position from the outer bearing | mm | Distance from the outer bearing to where the catalogue allowable applies (often mid-shaft extension). |
| Actual load position from the outer bearing | mm | Distance from the outer bearing to the centre of the hub actually fitted. |
| Distance between the shaft bearings | mm | Centre distance between the two bearings of the shaft. |
Method and formulas
- Torque T = P ÷ ω; overhung load = 2T ÷ D × factor.
- Allowable at the actual position ≈ catalogue allowable × L_c ÷ L_a (equal bending moment at the outer bearing).
- Outer bearing load = OHL × (S + L_a) ÷ S (lever over the bearing span).
- Example: 7.5 kW at 100 rpm on a 200 mm sprocket gives 7.162 kN against 7.5 kN allowed.
Limitations
- Simple lever correction; use the maker’s position factors where published.
- Factors are typical values for the element type; tensioning practice changes them.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Check a sprocket or pulley on a gearbox output shaft
- Decide whether to move the hub closer or add an outboard bearing
- Compare chain and belt drives for shaft load
Who it is for
- Design engineers
- Maintenance engineers
- Power transmission engineers
What you get
- Torque and overhung load
- Allowable at the actual position
- Outer bearing load
Interpreting the result
- Mounting the hub tight against the shaft shoulder is often the cheapest way to cut bearing load.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 2487–2556, 2365–2416. Topic reference; no source tables or recommended settings are reproduced.
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Open the Overhung (Radial) Load on a Gearbox or Motor Shaft calculator
