Gear ratio

A gear ratio compares how fast the motor spins with how fast the joint it drives turns. At 100 to 1, the motor turns 100 times while the joint turns once.

The joint gets roughly 100 times the motor’s turning force in return, minus friction. It works like the low gear on a bicycle.

Walking robots often use low ratios, around 6 to 1 or 9 to 1, so their legs can absorb the bump of each step. Precise factory arms use high ratios to hold their position firmly.