Reduction Ratio & Backlash, Explained

Two specs buyers see on every datasheet but often misread — what they really mean for speed, torque and accuracy.

What reduction ratio really does

A 100:1 reducer turns 100 input revolutions into 1 output revolution. In exchange, output torque is multiplied (minus efficiency losses) and output speed is divided by 100. This lets a small, fast servo motor drive a heavy load slowly and precisely. Choosing the ratio is always a trade-off between speed and torque/resolution.

Backlash and why "zero" matters

Backlash is the small angular play you feel when the output is reversed. In conventional gears it comes from tooth clearance and grows with wear. In precision motion it causes positioning error and vibration at reversal. Harmonic drives keep multiple teeth in constant contact, so backlash is effectively zero — measured in arc-seconds — which is essential for robots and CNC positioning.