pic: 121 Manipulator Prototype

The before and after of one of our manipulators. We are now building another more advanced device. Check out more photos at www.joemenassa.com

This appears to be an end effector that can grab the ringers. Can the top and bottom drive opposite one another so that the ringer can twist in place? How will you control this?

What are the tubes and “pully” things made out of? where can I order some!!!

Yes, the top and bottom can move independently. We are using two windows motors: one driving the top and the other driving the bottom. The window motor that drives the bottom is hidden from view. Go here for the latest episode of American Robot to see it in action.

The tubes are just regular 'ol PVC you can buy at any hardware. They’re great to prototype with. The pulleys I believe are from McMaster, but I don’t know the part number (Rob could answer that).

The belts are “polycord” material, they come in length, you cut them to the length you want and fuse the ends together to make an endless loop. You can order them from McMaster or from Smallparts Inc.

I’m actually going to use some 1/8" cord for the tracks for my 3lb combat robot.

The belting is called Polycord. I got the belts and the pulleys from McMaster. Search for “round belt” and for “round belt pulleys” .I hope your credit card has a high limit.

Good Luck,


Have you thought about how you are going to confront the issue of side-load on the belts?

We have run extensive tests on this type of system, and have determined that side-loads generated from twisting the tubes can easily dislodge the belts.

As for belts, I highly recommend neoprene belts from mcmaster carr. They have incredible traction.

I machined our own pulleys out of nylon (18 hrs. of machining w00t w00t!)

I’m fairly sure I’ve seen a video of this manipulator in action somewhere, and all I can say is AWESOME. Killer design, it should work great. (And if this is just a prototype, I’d hate to see the real one)

The latest episode of American Robot (see my post above) has the gripper in action. One polycord was a bit bigger than the others, so it rolled off once or twice. We always cut an extra inch off the polycord before bonding it together…generally give a tighter fit.

The next design iteration is going to have shorter jaws anyways, and might have double pulleys…so in the rare event one does fall off, there will be back-ups.