PVC Rollers?

I’ve asked this before on the forum last build season, and absolutely no one replied :frowning:

So I’ve come to ask it again.

Can anyone link me or show me where to get PVC rollers for conveyor systems utilizing polycord?

Last year we were so misguided we ended up buying those foam rollers (the ones used for exercise).

Thanks in advance.

I’m not sure what foam rollers you speak of, but a lot of teams just purchase PVC from Home Depot or a similar store for their rollers. It is just pvc tubing that teams can machine grooves into or put rings around the PVC pipe to capture the polycord in place, but it is nothing special.

Other teams use other materials for their tubing: aluminum, acetal, polycarbonate, etc.

I don’t have a picture on me, but for some of the bots I saw, the grooves were HUGE and DEEP.

Like, anywhere from 1/4" to 1/2" deep. I haven’t seen PVC with a wall that thick, unless they were using a bunch of small segments of PVC connected by some sort of fittings to simulate grooves.

I’ve seen more ABS rollers than PVC. ABS plastic is more appropriate for this type of application (less shatter-y, rougher surface finish), and generally comes in thicker walls, which can be machined. However, it can be much easier to add grooves onto the surface of a roller than cut them into it. The solution can be as simple as a couple of donuts cut from plate stock and epoxied to the surface of the roller.

McMaster catalog page

There are a variety of sizes and material options. Take a look around McMaster or Grainger searching for ‘Conveyor rollers’ and you’ll turn up some more.

For what it’s worth, 95 used some rollers from McMaster last season and they worked out alright. We ran actual conveyor belting around them. Our early tests using polycord was suggesting it was going to be more trouble keeping them on track then it was worth in weight savings.

On 330 we just cut thin sections of PVC pipe and then make a slit in the resulting ring. The sections are then glued to the main roller on either side of the spot where you want the belt to be using PVC cement. Simple, effective, and cheap

We prototype using PVC with wood plugs in the ends and 1/4 20 bolts sticking out long enough to put electric hand-drills on for proto-power…

On production, we use hollow aluminum tube with Nylon plugs in the ends and we press aluminum shafts in, spinning on lubricant-infused bushings… I think going forward we’ll skip the bushings and use sealed-bearings if weight/cost isn’t an issue.

As for keeping Polycords in-place… we abide by the 148 Robowranglers credo… “IF gum-rubber isn’t the answer, THEN you’re asking the wrong question…”

LOL

SERIOUSLY, the black gum-rubber works great creating channels and looks awesome!! < some scrolling pictures www.broncbotz.com > You need to apply at least TWO layers and super-glue each layer…

From McMaster:

4568T18 Architectural Anodized Aluminum (alloy 6063), Tube, .065" Wall Thk, 1-1/2" Od, 1.370" Id, 6’ L
93625K58 Natural Gum Foam, Adhesive-backed, 1/8" Thick, 1-1/2" Width, 50’ L
8541K56 3 Ft. Wear-resistant Black Nylon Rod, 1-3/8" Diameter

We machined them from 2" delrin round stock. Very simple to do.

We did the same… expect out of 1.25 billet 6061.

This is exactly what we did as well, but with Polycarb tubing. It requires no machining time other than a bandsaw and provides the same function.

Do you do anything to fill the gap that spreading the ring makes? We did this method one year, and it worked, but looks left more than a bit to be desired.

'Tis just standard PVC and end caps (obviously drilled into them for the axle) purchased at the local home depot. The rings around the PVC that keep the polycord in place are just strips of another pipe of a slightly wider diameter (It may even be a end cap that we chopped up and slid on, I don’t remember exactly).

http://team2495.com/images/rollers.png

It’s great to mention and bring up in this topic regarding what materials you should use for your rollers. Everyone knows a combination of ABS, Delrin, Aluminum, PVC, ect. Another one to throw in there is wood and 1114 used it effectively this year on their intake. It’s just a great thing to remember that some of the most “effective” components of a system may just be in a scrap pile in your high schools woodshop. :slight_smile:

If you’re specifically interested to machine a roller from PVC then you might try schedule 80. It’s thicker than Schedule 40 and usually dark grey.

McMaster sells it.

We have used it in the past with polycord. It worked well.

I ADDED to my above post the materials we use purchased from McMaster.com

Hope this is helpful…

This year 447 used schedule 40 PVC pipe has the roller and rather than machining grooves into the roller we used the corresponding PVC coupler. We only used the ends of the coupler as dividers. You can glue them into place, but I do not believe we did and they held up just fine all season. This works well for teams with limited machining capabilities since all you really need is a saw to cut the pipe and couplers.

It’s also worth noting that with some research you can match up sched 80 ID’s to sched 40 OD’s to create nice and tall rings for your urethane belting “grooves”.

We’ve done this on a couple robots starting in 2009. Our 2009 robot had something like (11) 22" wide rollers where the cost of ABS or Acetal was becoming an issue. The PVC on PVC rollers are super cheap, really light and easily reconfigured.

-Brando

No but we did end up adding the gum rubber which Michael Blake provided the part number for.

Our end caps were just UHMW disks with a hex in them.

In 2011 we cut PVC couplers to act as guides for our Polly cord with no groves at all. We wanted its to act as a slip clutch for our rollers on our claw that year. All in all it did the job. It had enough friction to pick up the tubes but not enough to stall out the motors once the tube was all the way in.

http://sphotos-a.xx.fbcdn.net/hphotos-snc7/293387_10150324530808987_451419175_n.jpg

Last year we cut grooves directly into schedule 80 PVC and it worked pretty well as long as the cord was tight. Once the cord stretched a little it started to walk out of the groves but to fix it all you had to do was cut it and tighten it(probably like once a competition). The grooves where just shy of half of covering half of the cord which isn’t ideal but worked all season long on both team 1592s and team 801 twin robots.

http://sphotos-b.xx.fbcdn.net/hphotos-ash4/420143_10150637609968987_904262382_n.jpg

Looking back on this season I would Probably go with some ABS just so I could get a deeper grove but if is all you have access to its pretty cheap and its everywhere so go for it especially on a prototype. The Nice thing about first robotics is that there is more than one “right way” to solve a problem.

We used 1/16 thick clear polycarb rollers this year on our front convayor. It worked very well, no problems. Polycarb is very durable and springs back unlike thinwall aluminum tubing. We used thinwall aluminum for rollers inside the robot to reduce weight.

Instead of larger diameter rings I would suggest a belt comb. This year, we began with no belt combs and ended with a belt comb on all of our polyurthane belt runs. It’s not that PVC rings don’t work but a comb ensures that the belt can’t walk down the roller. Even if you pull the belt off of its “spot” on the roller it’ll walk back. If we use polyurthane belts in the future, which I’m sure we will, you can be sure that we will also use a belt comb.

Regards, Bryan