Work out servo torque requirement instantly with clear inputs, formula shown and shareable results.
Servo torque must cover the static gravity moment (mass x g x arm) plus the inertial term (inertia x angular acceleration), then a safety factor. Treating the load as a point mass gives inertia = m r squared, and the arm length appears squared in that term — so a long arm is dominated by acceleration, not gravity.
Servo torque
T = m g r + m r^2 x alpha, then x safety factor
Friction, cable drag, unmodelled inertia and voltage sag all reduce real torque. 1.5-2x is normal, more if the motion is fast or the load uncertain.
Gravity load must be held continuously, so check the motor's continuous rating, not its peak — peak torque is only available for seconds.