Fancy Schmancy Wheels
 

I've been playing around with Inventor over the last two weeks while simultaneously experimenting with some more unique ideas for drivetrains. Thus far, I've been using Ed Sparks' models of the 8" diameter wheelchair wheels, but I don't like the solutions I've found for mating them with sprockets. Also, I wouldn't mind something with a bit better traction.

So, I thought that we could design and build our own wheels this season - as I've seen lots of other teams do this. My question, though, is how do you do it?

http://www.theforumisdown.com/upload...ling_bling.jpg
(You may have to copy and paste.)

This is what I had in mind, and I'll add Brecoflex belting to the outside, in theory.

But, how would I make it? What machinery would we use? It looks like we'll have access to anything I can imagine this season, including several CNC mills, CNC lathes, CNC punches and CNC sheet metal bender-things.

Any ideas? Some help? My bling-bling quotient is severely lacking.

The link is a no go for click or copy paste.

Also, according to my understanding of last years rules, you could not have machined wheels larger than 6". Stock that large is not nearly allowed by the additional hardware list and 6" is the biggest Small Parts carries.

Check out 122's wheels from last year, they were almost exactly like that and fairly large....

in past years we have done everything from cutting off the rubber from the wheelchair wheels and adding new traction to making our own wheels our of wooden circles (aka: last years)...take a look in the gallery for ours...

http://www.theforumisdown.com/uploadfiles/1102/bling_bling.jpg

Copy and Paste that

Not bad at all. I would have the wheels wider though.

Also, can someone tell me how a custom machined wheel larger than 6" is (was) allowed?

Well, that's just one wheel. There would be 4 per side, in theory.

If you were able to get stock that large. . .or, even 6". . .how would you machine it to get that sort of object?

We did something exactly like that last year. The wheels were machined with an automated mill at our high school I believe. In fact, the wheels got messed up so they had to machine some new ones this past weekend.

The problem with the bicroflex is adhering the stuff to the wheel. We did have a compound that adhered it rather well. We were using the green bicroflex belts, but they didn't offer enough traction, so we went to the brown bicroflex at the cometitions. We attached this to the wheels by drilling holes in them and riveting the belt to the wheel. It worked, but eventually the belting wore down and had to be replaced (which is why new ones were machined).

I know we had CAD drawings on our team's website, Team 93, but they don't seem to be there. Check back some time and the cad drawing should be there.


You can see the brown belt on the right (rear) wheels, and the green belt on the left (front) wheels.

nice bling, but can u go against these?
 

crap the pic isnt on this computer, ill update it later


BAd

As long as you can make it out of allowed raw materials, and it doesn't violate any of the other rules(no razor spikes for traction due to carpet damage, etc), you could have wheels as big as you wanted...

The biggest metal shaft allowed was 1 or 1 1/2 in. The biggest aluminum extrusion allowed was 2x3 cross section. The thickest plate allowed was 1/4. None of these would really be useful in making wheels. All the wheels I saw were much larger than the allowable stock. Also, wheels could only come from skyway or be a caster. Was there special permission given in a team update or e-mail?

SPI
 

Small Parts has (had?) 6" round stock aluminum.

Andy B.

You could always take a few plates, cut them to size, and fasten them together somehow....or use the stock from SPI that Andy mentioned...

Keep in mind also that the wheels only coming from Skyway or being a caster only applies to pre-fabricated wheels...if you use raw stock, you can make anything you want(except things like springs, which are specifically disallowed.)

now im set....
 

hey,

last year our team made some pimpin wheels, u mighta seen TheWheelMan pushing our wheels in the pits last year...

What we did...

took 6" blanks of round stock..
hogged out the inside to the our drawings,
made a set of soft jaw chuck for our prototrac,
made a bolt hole pattern, and drilled a hole in the center of where our spokes were,
ran the prototrac to cut out all of the spokes.

then we went to the turret lathe, and made a series of grooves and vees on the face to provide traction without damaging the carpet.

wanna pic? here ya go!(it in a post of mine)


Bad[url=http://www.chiefdelphi.com/forums/showthread.php?threadid=14256]

Who ever went to GLR knows who had the "Pimp" wheels. HOT BOT!.. Their spokes where flames and chromed out! Now that was "Pimpin' It" :D

Hot Bot 2001 & 2002 made their wheels by cutting the center plate with the flames and bolt pattern out of what looked like 1/4" aluminum, then wrapped aluminum around the circumference to add width and welded the two together and then added traction material. It was very effective.

Someone from Hot Bot can probably fill you in with pics. Other than that 6" Aluminum Round Stock was the largest you could use to make 'billet' rims for your bot.

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

Wow, That wheel is like almost exactly the same as our robot's wheels from last year.

http://www2.wildstang.org/ws/inventor/2002/as/as32.jpg

I thought I'd mention this to you. In the picture above, you should be able to see the extra bracing that we put on our spokes. During our practices we had found that without them, 4 of the 5 spokes broke away from the center. These were not made to be dragged sideways across carpet (like what happens when you do a 360 with a 4 wheel drive bot) so keep that in mind.

I have no clue really as to how our wheels where made or exactly what from.

Truthfully, I don't know what the stuff was we used. It wasn't brecoflex, I had the wrong impression of the stuff. Sorry, I was wrong.


I wish I had a link for it, but it worked really well. It's much like the stuff on 535's wheels (link on previous page).

The wheel tread material posted on the previous page and on the Hot Bot wheels I believe is 'Equipment Mounting Pads' from Small Parts Part No. U-PAD-6 3/8" Thick available from 4"x4" to 24" x 24"

Word to the Wise: Order now since Small Parts supply is exhausted for the season in the first few days of the build as many have found out in past years

Last I heard FIRST was supposed to be getting a new supplier so it's probabaly better to wait.

Here's a quick rundown on how we built our wheels.

1. Draw cool flame pattern in AutoCAD
2. CNC machine (or water jet) spoke plate from 1/4" Al.
3. Machine a 1/4" wide spoke slot in 2" X 12"*pi Al. plate
3. Anneal 2" Al plate (heat it up with a torch to make it softer)
4. Roll 2" plate into 12" diameter
5. Weld the palte to the spoke (the spoke plate is constrained in the machined slot)
6. Weld 1" Diameter X 2" Al round stock to center of wheel
7. Chuck wheel into lathe and bore axle hole
8. Broach keyway in the axle hole
9. Mount whell on an axle and turn outer surface
10. Glue tractioin material to wheel.

Presto.... "Pimpin Wheels"

Oh yah and don't forget to polish them before welding.

We pulled 220 lb. on SPAM's (I think) pull station at nationals.

I have pratically almost all of the manual memorized from the 2000, 2001, and 2002 game. Let me know if I am wrong, but isn't it illegal to have a fastner (screw) type device on the wheels? Or do they pass until they tear up the carpet?

yep, those are our wheels. made them by using a jig we created to cut out the sides, very hard work. and the metal wasn't heated, just rolled on a machine we have our at the other high school. sides were welded to the rolled aluminum and then we cut out the middle of a 60t sprocket, tapped it, and screwed it to the wheels. then we rivited neopreme around them, later we added neopreme pegs at our regional, and then spikes at nationals which we were forced to take off, so instead we added neopreme between the spikes and clamped them together making a vacume effect. if you talked to me at bash i probably mentioned something about the wheels. and they have a 12 inch diameter, 4 inches accross.

yup....they pass untill we destroy the carpet, (which we did at nationals) i have a picture of the new spiked wheel covers with neopreme somewhere around here, no pictures of the ones with just spikes. they took about 20 minutes of convincing the judges just to let us try them, and they resulted in a 20 second practice round for us (probably the shortest one anyone got)

well.. you got the 20 seconds to at least know if you move or not. myself and the rest of the floor team on 84 showed up to our first match at both MidAtlantics and Nats last year with never running the robot before. :rolleyes:

they are really nice wheels, to bad they didn't attack the carpet though. how long did it take to make something like that, and you probably didn't do it with a band saw and a scroll saw I'm guessing! ;)

DQ4: Deliberately damaging the playing field, controls or balls is strictly illegal and will result in disqualification of your alliance. Robot wheels must not, for example, damage the field
carpet. This will be checked during robot inspection at registration on the first event day and throughout the competition. Bunching up or puckering the carpet is considered damage to the field.

nope....everything on there was made by hand by myself, frank, dan and eric. they took about 4 hours each to make the complete wheel. cut out with a hand jigsaw....fun stuff

hey John,
um...er...no, we never made any cooefecient calcualtions, well at least that i know of. after the season was over, we fooled around with team 60 style tread, and they worked alot better, although u gotta admit that those were some pretty nice wheels. i would make a new set of those wheels, but we decided not too, we are going cheap this year.
hope u liked them
:)


bad

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Pulleys work very well. You can get them any size you want.

This is the first year we had too much power. We ripped 4 tracks right in half. we found out it only takes 750 lbs of torque to rip a Breco Flex timing belt.

We connect all are sprockets by a square shaft. this way we do not need any type of set screw, they will self alien

in-lbs or ft-lbs?