Or if you look in the gallery you'll come up with this:

If anyone from 67 is reading, I'd like to know more about how about you made those beasts :)

As of now, I'm considering reducing their width to 1/2" and making them from one sheet of aluminum and one sheet of polycarbonate bolted together. . .or, some variant of that.

Re: now im set....
 

Yup, those sure are pretty wheels. Great example of HSers making something truly beautiful.

But...
You guys talk about these things like they are the greatest things. I've heard they weren't all that great for pushing. Did you ever calculate a coefficient of friction value for them? I'm curious. I know for a fact that the "team60" tread is better, and brecoflex is even better than that...

Calculate it, and let me know.

Actually, those wheels were made by team 263. I dunno if they are more than 6 inches in diameter, but they look like it in the picture. They definately look like they were made how Reiland said. If you look at the inside of the wheel on the left, you can see a separation between the plates on the wheel. Looks like they just took aluminum plates, and heated them up with a torch (which tends to make aluminum more maleable). Then they formed them and held them together by welding spokes on. I could be wrong though.

Some more wheels:

401: Picture 1 Picture 2

535: Picture 1

263 (another picture): Picture 1

188 (these guys could pull a lot): Picture 1 Picture 2

522: Picture 1 Picture 2

58: Picture 1

67 (man that's a big wheel): Picture 1

353: Picture 1

Team 357 created these wheels for use with the 2002 Jester. The wheels provided excellent traction for pushing and resisting lateral motion, however, the wide, flat profile of the wheels meant that turning was only possible in low gear. When the Jester was in high gear the motors tended to stall. The wheels were strong and good looking but...the wheels required a great deal of machining time and may not have been a good use of valuable and limited build time.

HOT Wheels in Close
 

Here is a picture of the HOT Bot wheels from inside the chassis

Remember: The 6" limitation Only Applies to people that are machining the wheel from solid stock since that was the largest diameter available from Small Parts. Wheels like the HOT Bot are made from flat stock (you can see the welds from the spokes to the flat outer rim in the picture)

The omni-wheels or the square wheels (the wide ones)? They are made by a water jet, then other steps, I'll try and get someone else to answer you and help...

That wheel that you have M. Krass looks like it could be made using a lathe and a milling machine.

Don't worry about it, I'm not asking for help...I was reffering to the wide ones because they are similar to the ones M rendered. I do like the omni-wheels though.

*remember, we have 4+ of your old members on our team, we know what we need :D *

Oh yah, thiefs! lol, I was sorta offering to help M. Krass and just give ideas. An how come you all aren't registered for Nats yet?

Well, thanks :)

I don't have a lot of experience with milling machines. I just assume they can do whatever I ask, but I know that isn't the case, so I just wanted to check if they could do the job.

What I've settled on, I think, is two pieces of 3/8" polycarbonate cut to a similar pattern and bolted together to form a 3/4" wide wheel. Then, we can attach belting to its circumference, or whatever other material suits our needs.

I'll post a screen shot of what I have in mind this evening. I decided to do it this way because it can be made from sheet stock, rather than looking for enormous round stock that is still kit legal. They're also reasonably light (.5 lbs each), which is also good - especially when there may be 10. ( :) )

10 wheels?!? I wanna see that!

The bot is only as strong as the strongest material.

With that stated, how are you going to attach the polycarbonate wheel to your shaft? Keyway? Setscrew?

Although polycarb has a very high impact strength, I am unfamiliar with its tolerance of high forces for long periods (tensile strength). If a keyway is used, will it hold as the shaft rotates and high forces are created? This is one of the things you will need to figure out.

This webpage might help you to evaluate this.
http://homepages.which.net/~paul.hil...rialsBody.html -table form, easy to read, but you may have to look up some terms
http://students.villanova.edu/robotics/howto.htm -more pros/cons
http://www.matweb.com/ -material specifications for pros

If you look on the first site, Polycarbonate has a maximum working temperature of 138 degrees C before it loses much of its tensile strength. Will friction approach this temperature, allowing your keyways to melt through the polycarb like butter? You'll have to find this out. It's better to figure it out now, then to figure it out when your shafts are rotating but your bot is going nowhere during the match.



One problem with 10 wheels is turning the robot. One thing you could do is like we did last year. We used pneumatics to lower a caster that raised the front wheels up. Granted, you will be able to turn mor accurately if the caster is on the rear wheels, you might want to try something like this. It used a wedge design to gain strength to lift the 130lb bot with a small 3/4" cylinder capable of only lifting a maximum of 30lbs. This is the only picture available, but if you look at the preship video, or the regionals video, there are better shots of the robots systems.
Drive picture Team 93 website

Yep. I still have some concern about the polycarbonate, but it seems like a good bet. Another, slightly heavier option that I'm considering is sandwiching a 1/4" piece of aluminum between two 1/4" polycarbonate sheets.

We broke polycarbonate in a collision last year, so we're intimately familiar with its potential for failure :) But, then, we were also lucky because it wasn't structural.

Set screws suck ;) I usually just design to bolt through the wheels and sprockets, as I've done for this. While a keyway is an option, bolting through the wheels circumference (or near it) has worked fine.

My biggest concern is that the rim may break between the spokes. I hope that since the weight will be distributed over 6 to 10 wheels, it won't be a considerable obstacle. We can test this.

240 dF is a lot of friction :) Friction is bad. I love bearings. :)

Turning won't be a problem ;)

I'm not referring to that friction. Mainly, friction of the keyway interacting with the polycarb, and friction of the wheel interacting with the playingfield. I know our wheels got rather warm after matches last year.

Putting aluminum between the sheets of polycarb is a good idea. It may make your life harder, but it may be a much wiser move in the long run. One thing you could do, is put aluminum plates on each side of the wheel, and then use the polycarb as a "filler" between the two aluminum plates. Then you can make wheels as wide as you want with little weight gain, while still maintaining strength. Wider = better, traction wise that is. Turning may be difficult though.

Same as Brecoflex?

www.brecoflex.com