Polycarbonate Tube Shooter Rollers

I’ve seen a few teams try out Polycarbonate shooter rollers and I’m interested to see how they work.

We use polycarbonate tube intake rollers and have now tried that 2 different ways by having 3D printed end caps that we bolt from the outside, and then this year we are using the VEX intake roller product that clamps the polycarbonate tube from the inside.

How are the shooter ones spinning at much higher speeds being done? Bolt from the outside onto a 3D printed hub? Apoxy/Gluing the hubs on?

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I suspect you may need some beefy hubs or gears to drive the shooter rollers - for the inertial properties. The tubes themselves (unless you get the thick stuff) are far from a drop in replacement for a shaft full of wheels.

I believe I read that Orbit used aluminum rollers with silicone tubing in top. They had a lot of expansion when they reved their shooter up to full speed.

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We used the silicone sleeves for our dead axle rollers as well and had a similar problem. When we revved our rollers to shooting speed the silicone ballooned. To fix this we superglued the edges to the aluminum bars and glued Tessa tape around the ends. This tape basically doesn’t stretch laterally so it won’t expand with the silicone. We haven’t had any problems since we started doing this.

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Also, we didn’t try polycarb tubes, but not for engineering reasons, but because 2in polycarb tubes are hecking expensive, and 2in aluminum tubes are considerably less so.

As for the hubs, we 3d print them, and make it a really tight press fit (print oversize and then sandpaper them down until it’s close). We then bolt in 2 from either side, making sure that it’s balanced, otherwise it gets real loud and shakey when you get up to 6,000 rpm…

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Is that a local discount thing? You can get 2” OD polycarbonate from McMaster cheaper than any equivalent aluminum tube, even with a lower wall thickness (from my cursory search).

What thickness wall aluminum tubing did you run? Any issue with bent tubes from impacts with things like stage legs or other robots?

The intake, flip-up, and shoot motion on 2102’s robot this year was really slick, I’m impressed with how you made the roller setup work at 5k RPM.

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We used 1/16” wall thickness and only had one issue with the bars bending but that was when we drove full force into W.A.R. Lords at Hueneme Port. Otherwise we liked the aluminum for the weight, rotational inertia, and the bolts would probably cause the rollers to wobble when revved to shooting speed with polycarb rollers.

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Thanks for the info and congrats on an effective design!

-Mike

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We bent one tube in, pretty badly after going after a contested note in the center (against a UTB on WARlords). After that, all we had was a tears in the silicon tubing maybe twice, but no more structural damage.

We saw a LOT of bent up OTB intakes, and even more frames bent from UTB intakes. So we decided that, we’re not going to go for contested notes (not just auto, but teleop as well). Cutting a couple cycle down from 10 seconds to 6 seconds is not worth destroying your intake and being unable to score the rest of the match. We are only 96 lbs and can accelerate very fast, it doesn’t take that long to get to the source and get one without risk to our intake. Combined with an snappy auto-retacting intake that keeps us inside our frame perimeter as much as possible.

@annavennemeyer or @cpaggron do you know what speeds we ran when intaking? Most other teams I saw, like… slurp up notes, but the moment we touch a note, it’s in. When we video it at normal 60fps and I frame-by-frame it, I literally can’t catch the transition.

Also, we have a special method of getting the silicon on the roller. A Vacuum! We have a investment table thing meant for making plaster casts, but I’m pretty sure you could rig the same thing up with a powerful enough shop vac.

Basically, make a T-joint with tubes, put the silicon in and wrap the edges around the outside. Pull vacuum on the button joint, and the silicon will pull to the edges, and you just slide the tube in and shut off the vacuum. No compressed air, no soapy water, no fuss.

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Just checked GitHub, we were running the front Vortex at 3000, I don’t remember if we had any reduction that would change the speed on the rollers, it was either 1:1 or 1:2 right?

We used the 1/16th wall stuff polycarb tube from McMaster on our latest iteration of our intake and then we have some clear grip tape on the rollers. We 3d printed endcaps and hotglued them in place. We did have one of the end caps break this past weekend but the tubes themselves are fairly well protected with the collision bar we added that takes the brunt of any hits or scrapes and protects the intake rollers and the shooter shafts.

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The ratio is .8:1 so the front roller should be about 3750.

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Just checked CAD. So 3000 rpm on the vortex, to a 30t pulley, out to a 24t on the roller, so we actually run the intake tubes at 3750 rpm. Puts the surface velocity of those rollers around 35 ft/s… no wonder I can’t catch it on camera, if ChatGPT’s math is correct, it goes from on the ground, to stopped in our intake in 0.0384 seconds.

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Probably, one of our mentors is really good at finding local industrial metal supply shops and getting materials at a bargain.

Likely also a factor of: the material you already have is always cheaper than the material you don’t have and need to buy.

That being said, I’m glad we went with aluminum. I’d genuinely be afraid running polycarb at 6000 rpm.

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We were also shooting to upwards of 5750 rpm for farther shots btw. Also note that we were able to run them slower too to intake effectively (especially for intaking while back roller is revved during auto as we don’t want to fire the game piece out immediately.

oh damn so we were shooting at 6000+ rpm 0_0

This is genius! This was the first year we’ve tried to get silicone on the rollers and it was a pain. Do you think this would work with just a normal shopvac or similar?

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just the way this picture turns out, it looks like your roller is taller than ur students, you sure this fits in frame perimeter, how’d you pass inspection!?!?

We haven’t tried, but I would think as long as you get a decent seal on the bottom of the T-joint to the vacuum then I don’t see why it wouldn’t work. We use more of the silicon tubing to keep it air tight, it’s just hard to see in the video because it’s all white on white.