Best belt size for a roller claw

We are getting timing belts from McMaster-Carr for our roller claw, but don’t know what strength is needed. What sizes have you used/recommend? The sizes can be found at


I reccomend going to using the urethane belts from this page:

My team used the 1" wide belts, McMaster Part 6075K15, on our claw this these allowed us to be able to rotate the tubes and we sticky enough to suck the tubes right in.

did you use crowned pulleys or just normal tube?

We used normal 2" OD .065" wall tube. We milled the end caps so that the tube sat in a recess and there was an overhang to keep the belts from coming off the rollers. This also allowed us to fillet weld the end caps rather than butt weld them.

Was the flange significantly larger in OD to keep the belts from jumping to the area of higher tension, or was this a nonissue?

For reference, would you mind posting the gearing specs so we can figure out the force at that junction? I’d love to know that information.

The flange was just there to keep the belts from popping off the rollers, I don’t recall it being much more than the thickness of the belting. To get exact info I would have to swing by our next team meeting to measure or have the students bring up the CAD. (I haven’t made a model for any of our parts in at least 3 years, I work out designs with the students in our CAD lab.)

The belts could ride back and forth on the roller and find their “happy place” to run.

I’ll see if I have some pictures of this at home (can’t post picrtures from my work computer).

The gearing was just a banebot 550 through a 64:1 reduction P60. On the output shaft of the banebot we keyed a 20 tooth #10 sprocket, which drove a identical sprocket that was 1/2 hex broached. The hex broached shaft drove the rear belt roller. The belts themselves drove the front roller allowing slip in case something (contact with the field or another robot) locked the more susceptable roller.

The belts are to control the wheels, not for the tubes themselves. Thanks for your input!

Pictures uploaded:
Prototype used for suffield shakedown.

Final design used from CT regional on.
Left side

Right side