7.6: Formulas

Speed = Distance / Time

Rotational Speed = Rotational Cycles / Time

Rotational Speed = Degrees / Time

Torque = Force x Distance

Force = Torque / Distance

        Where the Distance is the distance from the axis of rotation

Power = Force x Velocity

Motor Key Specs:

  • Stall Torque
  • Free Speed
  • Stall Current
  • Free Current

For determining motor characteristics as voltage varies:

New Value = Spec Value x (New Voltage / Spec Voltage)

For determining Motor Current Draw at a given Torque Load:

Current Draw = ((Stall Current – Free Current) / Stall Torque) x Given Torque Load + Free Current

For determining the Torque Load at a given Motor Current Draw:

Torque Load = (Given Motor Current – Free Current) x Stall Torque / (Stall Current – Free Current)

For determining Motor Rotational Speed at a given Torque Load:

Rotational Speed = -(Free Speed / Stall Torque) x Given Torque Load + Free Speed

For determining “Super” Motor Specs from Multiple Motors combined as one, geared to the same Speed:

Free Speed = SAME

Stall Torque = Sum of all Motor Stall Torques

Stall Current = Sum of all Motor Stall Currents

Free Current = Sum of all Motor Free Currents