Let's Make Robots!

Choice of servo

Im part of a group designing a quadruped robot. We require servos on the leg for one for vertical and one for horizontal movement. We undergone torque calculations for the robot to remain stationary which eg. calculated at 3.75 kg/cm. We looked at torque specifications on the servos and it gives you stall torque for hitec servos. I am unsure for what range of torque for the servo to select. Eg like 3.75 kg/cm for 5 volt supply what torque from the servo specifications must be selected? Please help me out. Also what model of the hitec servo must I choose. Not really worried about speed.

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If you calculated 3.75 kg/cm, then that is the minimum you need. You should look for a servo that has a rating higher than that.

A HiTec HS-545 has 4.4 kg/cm torque using a 4.8 volt battery. It has adequate torque, but the nylon gears may be a weak point. It might be better to use a HiTec HS-645 that has metal gears, for more durability. The 7.7 kg-cm torque would just be extra reserves.