You probably want CV joints instead of universal joints. There are some significant angles involved there, so the angular velocity will not be consistent.

yeah I did notice that. I'll look up CV joints and maybe refit it for that. Thanks!

Rzeppa > Tripod, especially since I don't think you need any plunge in this application. Get some good molybdenum lube and everything will work out right.

Trivia: one synonym for this type of joint is "homokinetic". :D

😳 Interesting

Ooohh that's wonderfully industrial

So freaking cool!

Are the universal joints being used as hinges?

yeah, looking back on it I see its not ideal. a CV joint would have been better

Wouldn't it be better to have a dedicated hinge instead of relying on the piston to keep it aligned and rigid?

Well, no. It has to be able to flex as well as have the wheels spin. The wheels are axially driven, each in a row and for that you need a UJ or a CVJ

I know. I meant that you were using a universal joint as the hinge of each finger segment, and that gave it three degrees of freedom. The piston strongly restricts/controls one axis (the intended bending of the finger segments), but only weakly restricts torsion along the axis the universal joint uses to transfer rotation and bending along the axis perpendicular to both of these (as in, it technically restricts the axis, but at an extreme mechanical disadvantage that would likely play merry hell with the components of the piston).