Gears are Old and Busted, Capstans are Cool

Gears are Old and Busted, Capstans are Cool

Zero backlash, high “gear” reduction, high torque transparency, silent operation, and low cost. What is this miracle speed reduction technology, you ask? Well, it’s shoelaces and a bunch of 3D printed plastic, at least in [Aead Musa]’s latest installment in his series on developing his own robot dog.


OK, the shoelaces were only used in the first proof of concept. [Aead] shortly upgrades to steel cable, and finds out that steel fatigues and snaps after a few hours. He settles on Dyneema DM-20, a flexible yet non-stretching synthetic rope.


Before it’s all over, he got a five-bar linkage plotting with a pencil on the table and a quadriped leg jumping up and down on the table — to failure. All in all, it points to a great future, and we can’t wait to see the dog-bot that’s going to come out of this.


There’s nothing secret about using capstan drives, but we often wonder why we don’t see cable-powered robotics used more in the hacker world. [Aead] makes the case that it pairs better with 3D printing than gears, where the surface irregularities really bind. If you want to get a jumpstart, the test fixture that he’s using is available on GitHub.




If you want to learn more about capstan drives, you absolutely need to check out our own [Sonya Vasquez]’s Cable Mechanism Maths. She brought some demos of her gear reduction mechanisms to Supercon, and they just feel like butter. (If I were a robot, that’s how ..

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