pic: Madtown Marauders Wheel


Hey CD,

Another product from team 1323 and team 11. One of our sponsors donated 13 of these awesome wheels aka Sunrise Medical. This is a 6 inch wheel which has to be lathed down to a 5 inch diameter due to the fact that is has a weird groove on the outside which does not allow us to put tread on it. The bore is 7/8, perfect for a 3/8th’s bearing. The wheel itself is plastic and weighs .05 lbs. It is made to survive 8 years on a wheel chair. Just a tad bit of background, Sunrise Medical is the Worlds leader in Wheel Chairs and other medical equipment. They donate $1500 dollars worth of materials every month; such as plastics, aluminum and wheels not to mention 24 V motors for offseason go-carts. The only problem we have is how do we attach a sprocket to it?

Help and opinions are welcome and greatly appreciated.

That looks awesome. Now what is the weight and its dimensions? Also how are you driving it?

Sorry, took a bit to write the description.

To be blunt, there is no way those spokes are not going to break.

I’m wondering the exact same thing. Unless the picture is at an angle and we don’t see the full spoke?

RC did tell me that Sunrise Medical told them the wheels were tested and tested again. They were concluded to be stronger than Al.

RC, did they say what plastic it is? Because although I would trust their engineers, I am a bit skeptical. Don’t know if they’d be fit for an environment such as FRC fields and matches.

Yeah, they did not say what plastic it is and they did say it is stronger than AL. These guys build quality stuff and their whole company is about quality. Cory, we have tried breaking these spokes and this wheel is pretty solid. We will test these wheels out before season starts. What i need right now are ideas about mounting the sprocket. Remember this wheel has to last 8 years on a wheel chair that holds a 120+ pound person.

You might be able to use AndyMark hubs and attach sprockets to them.

You can use the axle to align the hubs and wheel and keep things centered, and then possibly bolt through front to back (i think the hubs have six holes) and sandwich the wheel between two hubs or a hub and a plate.

You could maybe try pressing in a keyed hub of some kind possibly with jb-weld or some other strong epoxy as well. Unfortunately those wheels look really difficult to adapt to.

how about gluing a plate to the outer wheel rim and bolting the sprocket to that?

Here’s a link to a better view:


It’s not hard to use a wheel like this, but get ready for some machining. The easiest way I can think of is to make two plates that sandwich the wheel with half of the spoke profile milled into them each, so they fit snuggly into the wheel. Then use bolts to clamp the two plates together, trapping the wheel and using milled grooves and the spoke pattern to transfer the torque.

Then to power the wheel, either drill a hole pattern into these two sandwiching plates for a dead axle drive train, or make one of the pieces out of aluminum (the other could be polycarbonate to name an example) and broach it for a live axle.

[fist shaking/] argg… Dutra beats me to it… [/fist shaking]

Terrific their engineers might be, but I don’t think my grandmother or her walker would last long in a FIRST match :cool: Although I dare say she’d try and make me proud :cool:

BTW, your link is broken RC.

I fixed the link, it was being stupid!


We might hold these off for non competition robots too btw. Doesn’t have to be strictly for FRC either.

If you’re gonna go to all that trouble, you might just want to machine a whole custom wheel from aluminum.

We do make custom wheels and the weight on our custom ones are about .3 lbs. So I was trying to take advantage of these wheels and we have a ton of these. Machining out hubs won’t take as long as making new wheels. Thanks Art for the idea and we will test it out on tuesday of next week.

That is true, these things look pretty sweet for their weight of only 0.05lbs…that’s probably one of the lightest wheels to ever be used on a FIRST robot.

Are they really only .05 lbs? That seems rather unbelievable to me.

I don’t think anyone else has said it, but as you describe them I don’t believe they’ll be legal. They were surplus wheels given away? Not a product they continue to sell and any team can buy?

Yeah, they really are .05 lbs. When our team found them in the scrap pile and asked him why these are being thrown away. He told us too many for this month. We are making some more in february. We put them on the scale and thatz what they read. Also the first thing we did with the wheel was to break it by throwing it, standing on it and doing random things but the wheel did not flex. I think the wheels are buyable if you contact the company. Afterall they use them for their wheel chairs.

I assume these are designed to be used as caster wheels on the front of wheelchairs, and as such, I imagine would easily last 8+ years with no issues used in that application. However, when you use them for a different purpose (powered wheels driving a robot) the dynamics change drastically and I cannot foresee them having the same life span. That is not to say that it won’t work, but my limited experience with some of the higher strength-to-weight ratio materials leads me to believe that any wheel* that weighs .05lbs does not have the strength to make me comfortable enough to use them on a competition robot.

See if you can find out what the material really is, and that alone will tell you if they are truly stronger than aluminum (and exactly what sorts of loads they can handle). There is no sense taking someones word for it when there is enough information out there to double check for yourself.

Let us know what you find out. I am not aware of any plastic material that is less dense than any 6000 or 7000 series aluminum while also being stronger (or with remotely similar strength even).

It couldn’t hurt to re-weigh it too and put something else on the scale of known weight to get a basis for comparison. When looking at the second picture, it definitely looks heavier than .05lbs.