Hi All
Trying to use orange polycord to drive two conveyor belts. Having the same problem we always face which is the belts slip on the pulleys once a load is applied. We are using 1/4" belts on pulleys made from 2" PVC Dowels with a channel cut for a groove. The groove is not “V” or “U” shaped. Are we using:
A: Wrong material for Pulley
B: Too small diameter Pulley
C: Worng shaped groove
maybe a combo thereof or something else I’ve not thought of.
btw (our belts are 10% smaller than the circumferance
You’ll want to try a ‘V’ groove. The wedging effect of the V can generate a higher friction on the belt. Also the material of the pulley has an effect. The polycord grips onto metals better than plastic.
10% reduction in belt length may be too much tension and you are causing the rollers to flex and therefore bind. I would try to reduce the lengths to 3-5% reduction overall.
We are doing much the same thing but the rollers (usually) turn. Look at the rollers first. How difficult is it to rotate the rollers (with polycord-induced tension but w/o motors attached)? If you can’t easily turn them with your hands (but they need not spin freely), the polycord will slip. Try grease, better alignment, change polycord from 10% to 5% - something will work because ours work just fine.
3% stretch is working ok for us. We are using 1-1/2" ABS (about 2" outside diameter) rollers that are about a foot long. We’re using ball bearings in end caps to support the rollers. We don’t have any grooves in them, instead we have a simply plywood “comb” above the lower roller to keep the cords in place.
Pictures of your robot would help us help you figure out what’s wrong…
Here’s our comb. It doesn’t allow the cords to derail, they’re pretty well contained. But you have to experiment to figure out if it will work for you, it will not prevent the cords getting tangled up if for example the balls are trying real hard to push the cords sideways.
The rectangles with the diagonals are cut out to create gaps for the cords to move through. This particular one was designed to keep two bunches of cords together, not space individual cords. The final version that was use was significantly less material but this was the first iteration.
Circles are rivets to attach this to the bottom (or top) of piece spanning the run.
In the past, we have used PVC pipe (1-1/4 size, which is 1-5/8 OD) and then used the couplings as cord spacers. With 3/16 cord, we had about 5/16+ spacing.
Using bearings in the ends of the rollers helps considerably. There is a lot of tension on the tubes from the belts, and having a solid rolling surface for the bolts / axles is important.
We have used a 90% belt size in the past with no issues. They are tight, but stay tight through the season.
Jim (Mr. Forbes), what motor and gearing is your team using to drive the polycord rollers? Are you using solid or hollow (tube) polycord? Does thickness play a big factor, We have 1/4" tube, but have yet to fabricated lifter (hopefully tonight). Thanks.
