I read in ROBOT MAGAZINE of this new purple biped that runs off 55 oz/in of torque and it works perfectly.
Now the dynamixel bipeds use robotix dx-117 with 37 kg/cm of torque, which is a humongous number in oz/in (513.83).
I dont understand, is the torque so high because it uses aluminum brackets? I thought aluminum was lightweight.
I’m quite confused about the amount of torque I should have, regardless of what I require. 51 oz/in doesnt seem enough, not for pine wood parts, is it? How does 76 oz/in sound? 208 oz/in?
As far as humanoids go, one always wants a higher torque to weight ratio. I use the DX-117’s because they do have such a great torque to weight ratio - the only problem there is cost. The HiTec robonova uses servos that have a torque of 7.4 kg.cm (103 oz.in), but it is relatively light weight and small.
Personally, I wouldn’t want to use a bot that has any less torque then the RN-1. Robo-One class robots usually use servos that have a torque of 15 kg.cm or higher - this helps them move quickly and get up from any position (speed is lost if a robot doesn’t have enough torque to move). Smaller bots like Plen and Pirkus (which may be the purple robot you are referring to) can afford to have less torque because they are so lightweight.
It think it depends on the size of your biped. The smaller bipeds like the BRAT can run fine with 76 oz/in servos like the Hitec HS-475HB. Larger bipeds like the Scout require beefier servos like the Hitec HS-645MG (133 oz/in analog) or HS-5645MG (168 oz/in digital) servos.
It really depends on what you want the biped to do and how large it is. Above are a couple pretty good references to gauge things by.
