Keeping polycord on track

[jblay]

Your problem might be caused by having so much polycord. The tension of it could be causing the pvc to bend in towards the middle. This would cause lots of jumping. We experienced a similar issue in 09 so we stuck a piece of aluminum L the size of the inner diameter of our pvc through it to straighten it out.

[MrForbes]

Originally Posted by 45Auto

Put some PVC "rollers" over your guide rails, like you see in the cad model below. That simple fix made ours work unbelievably well!

That's a neat idea!

But I think we're doing something wrong on ours, we only have one set of polycord belts, and two rollers, to do the whole harvest/lift/load-into-the-hopper thing.

[45Auto]

But I think we're doing something wrong on ours, we only have one set of polycord belts, and two rollers, to do the whole harvest/lift/load-into-the-hopper thing.

I very seriously doubt if you're doing anything "wrong" , just make sure that multiple balls don't bind up on each other as they roll against each other.

The balls generate a lot of friction when they try to roll against each other. We've had bad experiences with single-feed systems with multiple balls binding up which led to our "dual lift" design with cords on front and back where the balls don't roll against each other.

Your system probably works better than ours if it's engineered correctly!

[MrForbes]

No, we do have the problem with multiple balls being able to easily jam in the intake. It's neat to see how you solved that problem.

The main reason we don't have much stuff on our robot, is because we're lazy....we'll spend hours figuring out how to avoid making more parts!

[artdutra04]

Originally Posted by LH Machinist

Use a belt length calculator http://www.durabelt.com/beltlengthcalculator.php
You’ll be surprised about how tight they are supposed to be. The “normal” stretch factor is between 8% – 12%.

In FRC applications, you only need 3-4% stretch.

[Jacob Paikoff]

We just put our polycord on last night and it didn't seem to have a problem. We're using pvc rollers wrapped in shelf liner which creates enough friction that the belts don't move side to side.