pic: Magic wheels

We were having trouble with wheels. We bought these poly wheels from skyway, but they were an inch less than advertised, and so unusable. We traded T45 for two more kit wheels, but they were too sticky and we didn’t manage to get them not-sticky.

So some of the guys came up with this idea. It works, and its a great conversation starter, so I guess it turned out to be a good idea.

The only kink was that we had to buy the marbles in packs with lots of little ones and only a few large ones. So we have a giant box full of little marbles. Heh, a neat little giveaway item for the competition, huh?

As of now, the marbles are just pressfit, and we stressed the robot pretty thouroughly without losing any of them. If they get to be problem, we can always glue them in, but then if (we haven’t, yet) we break any marbles, they will be a pain to remove and replace.

wow… that looks pretty cool

If you come to Saint Louis regional, we will give you some little marbles. For free.

You see, to get the big ones (on a short notice without having to get them shipped) you have to buy a package of marbles that contains 300000 little ones and 2 or 3 big ones.

So we have a ridiculous amount of small marbles left over.

The wheel was made like this: we put marks every inch on the wheel, drilled in with a 1/4" hand-held drill, used the press and a 7/8" bit to make the hole, rubber-malleted a 1" marble into the hole.

No glue or epoxy as of now, although it may be added later. We are still undecided, although we are leaning towards “no.”

I don’t know if you guys looked at this:

In no case, will traction devices that damage the carpet or other playing surfaces be permitted. Traction devices may not have surface features such as metal, sandpaper, or hard plastic studs, cleats, or other attachments.

I know it doesn’t say anything about glass or marbles but I think that would be up for interpretation. I would ask FIRST before I showed up to a competition like this.


if those are there to give traction then you might have a problem. Glass marbles aren’t exactly sandpaper. I have a lot of concern for the design. I guess I’ll find out at the St. Louis regionals. See you there.

It’s a cool design but I doubt it will pass inspection. You do realize the edges of the platform are diamond plate and the spinning wheel will probably shatter or chip the marbles when it comes in contact with the diamond plate. FIRST won’t be too keen on having to bring out an Electrolux and vacuum the field after your match. If you REALLY want to try to use these wheels I would suggest bring another set of wheels without marbles so in case you fail inspection you could change wheels.

The rule is to prevent carpet damage.

Those marbles will not damage the carpet. They slide, thats what they are there for. I think the hard plastic studs refers to object designed to dig in and stay put: these exist to make the wheel easy to slide around. Our back rubber wheels do more damage to carpets that the marbles. I don’t forsee a problem.

damaging the carpet is probably not going to be your problems but the problem will be that FIRST will not want to clean it up after every match. if those marbels break

I think you have hit on the real key here. As the wheels are currently configured, they MIGHT pass inspection. But the first time they chip on the platform lip and get a sharp edge, they would then pose a damage hazard to the carpet. At that point, you run the risk of being DQ’d.

My best advise: just in case, take an extra set of un-modified wheels with you, and practise on changing them out real fast! :slight_smile:


Cool looking! I like the trippy colored marbles, althoug I dont think i’d like them as much if one of them punctured our robots tires after one of your maches…

The rule is prevent field damage, not just carpet damage. It specifically states in the rule, “carpet or other playing surfaces”.

I think that the level of contreversy this is causing on CD alone is reason enough to check with FIRST to make sure you’ll be ok.
Looks cool though. Hope it passes.

Really good looking wheels but the first thing that came to my mind after reading your method of fabrication is “flying marbles”.
Under extreme conditions when the the rubber heats up and the wheels are spinning very fast. I would be afraid that the marbles will come out and go flying.

Something to consider-
From a previous robot inspector

yeah i would think you would want to hold them in with something if not epoxy then silicon rubber or even hot glue! and consider replacing the marbles with say teflon bals… glass is nasty when it shatters

If that frame around the wheel prevents the wheel from contacting the diamond plate, you should be in better shape. So if that frame is below 6" tall, I think you might be ok. It is still a hard call. And it you were planning on climbing the stairs, you could use the other two wheels (probably climb better than marbled-wheels anyway).

Edit - The frame would have to be really low, because of the smaller steps.