pic: Madtown Marauders Wheel
 

Re: pic: Madtown Marauders Wheel
 

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

Re: pic: Madtown Marauders Wheel
 

Sorry, took a bit to write the description.

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

Re: pic: Madtown Marauders Wheel
 

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.

Re: pic: Madtown Marauders Wheel
 

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.

Re: pic: Madtown Marauders Wheel
 

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.

Re: pic: Madtown Marauders Wheel
 

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.

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

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Here's a link to a better view:

http://www.team1323.com/Pages/wheel1.html

Re: pic: Madtown Marauders Wheel
 

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.

Re: pic: Madtown Marauders Wheel
 

[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.

Re: pic: Madtown Marauders Wheel
 

I fixed the link, it was being stupid!

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Lol.

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

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

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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.

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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.

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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?

Re: pic: Madtown Marauders Wheel
 

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.

Re: pic: Madtown Marauders Wheel
 

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.

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Sorry - I do not believe they weigh .05 lbs - maybe someone made a mistake in where the decimal point belongs? Who told you or where did you read a spec that says it weighs that much - you should check your source again.

.05 lbs is less than 1 ounce. There are no materials known to us on earth that are that low in density that can hold 120 pounds in the configuration of that wheel.

Re: pic: Madtown Marauders Wheel
 

Sorry guys, I don't know what to tell you. It is what the engineers told us at Sunrise Medical and it doesn't show up on either our bathroom scales or our scale at school. It measures every .25 lbs. So I guess itz under .25 lbs. :confused:

Re: pic: Madtown Marauders Wheel
 

Yea please just find out what material it is. And if you can find a scale that measures even smaller increments that would be cool.

As for mounting the sprocket, I would go with Art's idea. U have the machining resources so get to it:p

Re: pic: Madtown Marauders Wheel
 

If your custom wheel is .3 lbs and is set up for either a sprocket or live axle it will likely be lighter than or equal to the pictured wheel with a setup such as the one Art described to drive it. Combine this with the strength concerns mentioned by some of the posters and you may want to look at what you really gain before deciding to use this wheel.

Sponsor donations are nice, but the parts always need to be evaluated against the alternatives.

Re: pic: Madtown Marauders Wheel
 

I was thinking the same, I was just wondering i there could be a lightweight solution to mounting a sprocket to this thing. If I have to make an aluminum hub it will probably be more than the custom one we have now. So i'm gonna try it out and see what i can do what this thing and i'll post up a pic with a sprocket, hub and the wheel all attached in a few days.

Preseason Madness Rocks!

-RC

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You could always use them as idler wheels.

From what I've heard, the spokes at not meant to be torqued. Sure they may work fantastically as casters but until you can find a way to test how well the wheel takes torque, you can't trust them powered on a FRC bot.

-Vivek

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looks nice. but i agree with a lot of other people. in FRC i dont think it would survive. but off season stuff it would be great to work with. although for a wheel chair it may be great but think about when you put all of that torque on the center of that wheel. it would probable rip apart after a while.