KEVOS® MAKEOS · Power Transmission
Torque Arm Reaction Check (Output Torque, Arm Reaction, Anchor Pin Joint)
For a shaft-mounted gearbox held by a torque arm, what reaction does the arm put on its anchor, and is the anchor pin joint strong enough?
Check of the torque arm of a shaft-mounted gear reducer: the output torque from power and speed with a service factor, the reaction at the arm anchor from the torque and the arm length, then the pin bending, shear and bearing, the eye net tension and tear-out of the arm’s pin joint (as the clevis pin joint tool), against the allowable stresses.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Motor power | kW | Rated power of the motor driving the reducer. |
| Output (shaft) speed | rpm | Speed of the reducer output shaft. |
| Service factor (starting and shock) | Factor for starting torque, shock and jams. | |
| Arm length (shaft centre to anchor pin) | mm | Distance from the shaft centre to the anchor pin, measured perpendicular to the arm’s line of reaction. |
| Anchor pin joint | ||
| Pin diameter | mm | Diameter of the anchor pin. |
| Arm eye thickness | mm | Thickness of the arm’s eye. |
| Thickness of each bracket plate | mm | Thickness of each plate of the anchor bracket (fork). |
| Gap between eye and each plate | mm | Gap between the eye and each plate. |
| Eye edge distance | mm | Distance from the eye hole centre to the end of the arm. |
| Allowable pin bending stress | MPa | Allowable pin bending stress. |
| Allowable pin shear stress | MPa | Allowable pin shear stress. |
| Allowable bearing stress | MPa | Allowable bearing stress. |
| Allowable eye tensile stress | MPa | Allowable eye net-section tensile stress. |
| Allowable eye tear-out shear stress | MPa | Allowable eye tear-out shear stress. |
Method and formulas
- Output torque = 9549 P ÷ n × service factor.
- Arm reaction = torque ÷ arm length (taken perpendicular to the arm).
- Pin bending, shear, eye and fork bearing, eye net tension and tear-out (as the clevis pin joint tool).
- Example: 1,145.9 N·m gives a 3.8197 kN reaction; the joint is at 36.025% of its allowables.
Limitations
- Arm perpendicular to the line to the shaft centre; an inclined arm adds a component along the arm.
- Reaction from torque only; belt pull or overhung loads on the reducer are not included.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Check the torque arm on a conveyor drive
- Size the anchor pin and bracket
- Check a torque arm after fitting a larger motor
Who it is for
- Maintenance engineers
- Design engineers
- Millwrights
What you get
- Output torque
- Arm reaction
- Pin joint stresses and utilisation
Interpreting the result
- Doubling the arm length halves the anchor reaction; a rubber bush at the anchor cushions starting shocks.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 1535, 1720–1735, 2122–2160. Topic reference; no source tables or recommended settings are reproduced.
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Open the Torque Arm Reaction Check (Output Torque, Arm Reaction, Anchor Pin Joint) calculator
