# pic: MORE Robotics 1714 Polycarb Wheels

Here is one of our Polycarb wheels on our 2010 robot. We wanted them to weigh as much as possible to give us a low center of gravity, so they weigh about 2lbs each.

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Low center of gravity is good and all, but have you considered how the added weight will effect your acceleration with this yearâ€™s tight quarters on the field?

wowâ€¦those things are niceâ€¦ i wish that our wheels were that light

Wait, you wish your wheels were 2lb a piece? What are you using? Mecanums? If so youâ€™re not too far off at 2.5lb a pieceâ€¦

I mean, 2lb isnâ€™t exactly light for a wheel

well we are using 4 KOP AndyMarks, and 2 IFIâ€™s not too much more but those Lexan wheels look sick

Is this a 3 piece wheel, or a single piece?
If it is a single piece, what are the lateral screws for.

Beautiful wheels guys.

The wheels are layers of polycarbonate. Solid one inch material is expensive. As far as the weight, 2 pounds is an estimate, so I will weigh one at the meeting tomorrow.

Ah, I see now. Looks like 5 layers right? 3 inner and two outer.

Nice lookin wheels. Though if you wanted them to weigh as much as possible steel is a nice and dense materialâ€¦ :rolleyes:

http://www.chiefdelphi.com/media/photos/34998

Just in case you have not seen any of our robots before, we try to build as clear as possible.

Maybe he wasnâ€™t clear on that.:rolleyes:

Ok ok bad pun. But I couldnâ€™t resist.

*Clearly *I had no idea and was using the sarcastic smilie for no reason

Hehe.

I have to agree with Craig, there are definite acceleration issues when you increase the weight of a wheel. This happens because the added weight resists motion and will fight you every time you try to change your direction of rotation or speed of rotation. This means slower to get up to speed, slower to stop, and more force on everything that powers the wheel including the chain and axles.

I like the creativity to get the center of gravity lower, but I really think you should bring alternative wheels if these give you too much troubles in competition.

It wouldnâ€™t take that long to pocket these wheels if the weight became an issue, but knowing the guys on the drivetrain team this year, they probably took that into account when gearing, testing, etc.

Mass isnâ€™t the issue. Itâ€™s the Moment of Inertia (resistance to spin, which is a function of mass and radius) that could be the issue.

Per my rough calculations, the moment of inertia of an AM performance wheel and 1714â€™s Lexan wheel differ by about 25%, and the actual ratio is slightly lower than this as the AM wheel has extra material near the axle that I didnâ€™t account for. I assumed an AM wheel is a rim and 3 sticks that span the inner diameter and the lexan wheel was a solid piece of Lexan.

Since you guys have the robot, have you noticed any adverse effects on performance? Iâ€™m still of the opinion that these wheels are super slick.

Well, in this instance, the only thing that can change the moment of inertia on the drivetrain is the mass if the moment is too high. If itâ€™s too high for comfort, you could easily cut 12 ounces out of the wheel with a drill press and 6 holes while maintaining strength if they absolutely had to.

We had time to do some decent test driving, and mobility did not seem to be an issue. It was every bit as fast, if not faster than I expected.

That is a video of us driving, and if it seems a little slow to you, this is all in low gear. Unfortunatly, I didnt get any video of it in high gear, but trust me, for this game it is plenty fast.

Thank you for the advise though, I personally had no idea about wheel weight affecting mobility, however I am sure people on the drive train team took this into consideration when designing the wheels.