Spinning Cylinders

Technical Technical Discussion
1

Commercial conveyor rollers are either heavy, expensive or both. I have a strong preference for light, cheap and simple, so I have made a variety of cylinders during prototyping. We do not have a machine shop, so I have been trying different ways of attaching a roller to a shaft with other ideas.

We have:

  1. Made a wooden cylinder, pinned to a 1/2-inch shaft by drilling holes through the wood into the shaft. This worked well, but was heavy.

  2. Used a hollow shaft with friction-fit plugs in the ends (didn’t work so well).

  3. Inserted threaded fasteners into plugs fit into the ends of a hollow aluminum cylinder (we unscrewed one of them which should have had reversed threads but didn’t).

  4. Created a free-spinning cylinder pegged to the shaft by an external metal fitting fixed to the shaft with a set screw (this worked well, but took up a lot of shaft room).

I’m just interested in hearing how other teams without the ability to cut keyways dealt with this, and how you engineered lightweight, Poof ball-friendly rollers.

2

While we have a machine shop I think our method could be done with just a drill press.

We make a free spinning roller (Al tube with bearings pressed in the ends) attached to the frame using hex head cap bolts with the heads cut off.

Mount a gear or pulley to one end with 4 screw.

The gear method requires a motor mounted closely to direct drive the gear on the roller. The pulley allows for a remote motor mount.

Having the drive right on the end of the roller only takes up room that the balls wouldn’t go into anyway.

Hope that helps.

3

Rick,

It looks like you guys can put plugs in hollow tubes. Have you tried PVC? PVC (Charlotte Pipe, specifically) is lightweight and tough and you can put almost any kind of friction surface on with simple hand tools.

-Paul

4

Well, I’m not saying they are good… but… here is what we did with next to no tools.

(1) 12" long 1" PVC tube
(2) 1" long 1" PVC tube
(2) 1" PVC coupler
(2) Bearing that comes with the skyway wheels (we ordered a bunch of them)
(1) metal shaft

  • Drop the bearing into the coupler. There is a lip on the inside of the coupler that will stop the bearing from passing through.
  • Sandwich the bearing between the lip and a 1" hunk of PVC. Make sure the bearing you have doesn’t get squished by PVC and make sure it still spins freely.
  • Push this unit onto the 12" long PVC tube
  • Do the same on the other side.
  • Run rod down the center
  • The roller should now spin freely on a stationary shaft.

Now to the powering it part. We are using timing pulleys and belts. Replace the timing pulley set screw with a LONGER screw. Loctite or fix it so that it doesn’t touch the metal rod. Slip pulley onto rod, with the hub fitting into the 1" PVC. (Buy a pulley so that the hub will FIT inside the 1" PVC also.) Dremel a notch into the PVC for the long setscrew replacement. When we mounted the rollers, we also used spacers to hold the pulleys in place. It freaks the students out, but when it’s all spaced out, nothing can come apart.

Seems to be working right now… cheap, light, and easy to set up roller assy line staffed with people new to robotics.

5

Now I don’t know how much money your team has but I was recently turned onto a these really nifty quicklock clamp collars. http://www.mcmaster.com/nav/enter.asp?pagenum=964 (Third item down) When you tighten them, the inside gets tighter and the outside gets larger allowing you to clamp shafts onto outer pulleys. They cost from about 30-60 dollars depending on the size. My team probably isn’t going to use them this year, but in the future they’re definitely going to be a go to item for all our projects.

6

A remarkably helpful set of responses. Thanks!