Re: pic: Delrin Poly Cord Pulleys
 

In 2011 when we used 1/4" belting for our claw we had no problems with the connectors, however this year with the 3/16" belting it seemed as if we were always losing at least 1 belt because a connector came undone. I would attribute this to more likely too much tension on the belts but nevertheless something to be aware of.

Re: pic: Delrin Poly Cord Pulleys
 

We also used 1/4 hollow tube and had no issues with connectors.

Re: pic: Delrin Poly Cord Pulleys
 

So my worst fears as been confirmed, the .6 ID of these pulleys make them to flexible. Under the load of 4 cords there is about an 1/8 of an inch of deflection which makes them very stiff to turn. We are switching to 6061-T6 and with an ID of .66.

Re: pic: Delrin Poly Cord Pulleys
 

If you can, go with a much larger OD and use round hollow tube for the roller material.

1.5" diameter x 0.040" to 0.063" wall thickness aluminum tube works great for polycord rollers.

Re: pic: Delrin Poly Cord Pulleys
 

Agreed, in the 1.5" range you can find very nice rubber tubing to slide over the Tube to act as grip as well!

Such as McMaster: http://www.mcmaster.com/#87235K34 (comes in black btw :P)

We used 1.25 OD X .060 wall. It allowed us to press in a FR8 Bearings. So we drove one roller and made the rest dead/pressed in bearings.

-RC

Re: pic: Delrin Poly Cord Pulleys
 

Yup. We loved it.

If you can drop down to 1.25" 1/16" wall the bores can accept an FR8 bearing too, very convenient.

Re: pic: Delrin Poly Cord Pulleys
 

If you want to avoid grooves altogether, a plate of finger guides may work. See the bottom-left of this photo:
http://www.chiefdelphi.com/media/photos/37572

Re: pic: Delrin Poly Cord Pulleys
 

Nice, these look great! I wish I had those. I had to bang those out made out of wood on our homemade lathe. http://www.chiefdelphi.com/forums/sh...Homemade+Lathe