Polycord and Intake Rollers

Technical Technical Discussion
1

I made the video described in this thread here.

I show you how we weld our round polyurethane belts and how we make our intake rollers using large diameter latex tubing over aluminum tubes.

I also have a good post from last year about our round belts HERE

1 Like
2

Thank you for making these videos, we tried putting the tube over our aluminum tube this week and well it didnt go so well…

This will make it much easier.

What are you using to cap the one end of the tube? Any suggestions.
Thank you

3

Thanks for posting. If the surgical tubing is segmented, is it thick enough to create channels for the polycord to sit in?

4

Anything that will block air flow and take the pressure. We use inserted hubs. a chunk of wood wedged in would do it fine however. When all else fail, duct tape?

Probably will work, YMMV. It will need to be the thick wall stuff. You can tape an O-ring and do flat belt between the gaps, which is what we did last year.

5

Try the rubber stoppers for flasks in chemistry. Next try a champagne cork, (probably not something lying around at school ) that should be about 1.125" in diameter.

Thanks for the video Devin!

6

Anyone else have any questions about how we do any of these things? Or if you are looking for any advice.

7

Thanks very much! we just tried it, and it worked really well.

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8

Thank you so much for the video. It took us a few attempts and once we got it figured out rollers went on super quick.

For anyone doing this the first time.

  1. You must have an airtight connection between the air compressor hose and the rubber tube. We zip tied and used a hose clamp to stop any leaks from that end.
  2. Duct tape over the alum tube worked just fine to plug the end
  3. Have people with a good amount of muscle performing this take, it takes 2, sometimes 3 people to make it all work.
9

I’m glad that this has helped a number of teams! Anything else teams out there would like advice on to help out their build seasons? I can’t share what we are doing for our robot, but I can tell you about how we do some stuff in general no problem.

10

Thanks for the help! I had a few questions regarding flat belts -

What kind of o-ring would you recommend? Should it be undersized to stretch over the roller/pulley?

This year, we’re planning on using flat belts to transfer torque between shafts of our intake in both the traditional and crossed belt (like an infinity symbol) configuration. Have you ever used flat belts as a primary means to transfer torque? If so, any advice to share?

11

Solid, any suggested ID/ODs for the surgical tubing? All the ones I looked at were rather pricey per foot so we ended up trying bike tubes with good success. I have a hunch the surgical tubing would be both grippier and more durable.

For anyone curious - the bike tubes slide on reasonably well without air because you can scrunch them up and straighten them out. Takes a lot less strength to put them on. Just be sure to wash them with soap and water first because they ship with talc on them which will cause them to spin on your roller.

12

It doesn’t really matter that much, but it should not be loose.

Flat belt work great at torque transfer.

13

Almost anything will work here. We picked an O-ring that is only slightly undersize, and the only issue with it is that it does not always sit “flat” on the tube. Not really a problem, just looks a little uglier. No matter what you use, tape it down with electrical tape.

14

Here’s our setup: The ~0.75" wide ~1.2" diameter pulleys were made out of some colson live hubs from vexpro by cutting them in half and turning them down on a lathe. The flat belts are 0.5" wide.

We tried a few wraps of just ~0.25-0.375" wide electrical tape on the smooth metal pulley. It worked better than I expected. The belt tracked even better at higher speeds.

Would you recommend using an O-ring over using just electrical tape? I feel like a rubber band with some standard width electrical tape over it would also work. Thoughts?

Thanks for the help!

15

The only thing I’ve found is that the thinner the crown of the pulley, the better it tracks. And to some extent, the greater the difference between the crown OD and the pulley ID, the better it tracks. An O-ring is just a super easy way to achieve this. A rubber band would do probably just as well, especially doubled up. Even a piece of string of sufficient thickness, taped down, will do it. It’s really hard to get this wrong.

16

Where did you find black polycord?

17

West Coast Products wcproducts.net

I do not see a link for it right now however.

18

http://www.wcproducts.net/rollers-hubs

Product # wcp-0129