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Servo torque calculator ?

Enter the size of the control surface, the model's top speed and the throws. The calculator estimates the torque the servo needs and suggests one with a 50% margin.

Front to back of the moving surface (hinge line to trailing edge).
Along the hinge line, for the part this servo moves.
The fastest the model will fly, dives included.
The biggest deflection either way - 3D models can be 40° or more.
How far the servo arm turns either way for that - usually around 45°.

Result

Fill in the numbers above to see the result.

How it works

We use the widely used formula: torque (oz·in) = 8.5×10⁻⁶ × C² × V² × L × sin(S1) × tan(S1) ÷ tan(S2), with chord C and length L in cm, speed V in mph, surface throw S1 and servo throw S2 in degrees. One kg·cm is 13.9 oz·in.

Torque rises with the square of speed and of chord: double the speed and you need four times the torque.

The suggestion adds a 50% margin, because servos lose torque at lower voltage and as they age. Linkages with slop or flex need more.

Keep every model's numbers in one place RC Flyer Pro is a free logbook and hangar for RC pilots: your models, batteries, flights and flying field, with GPS flight replays in 3D. Start free

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