Wheels: Metal or Plastic?
 

Last year we used the AndyMark plaction wheels to good advantage. In previous years, the metal IFI wheels were quite good as well.

I'm wondering what others think, in terms of pros and cons, of each of these wheels.

Plastic: They don't break, but the thin lip holding the tread on sometimes chips off. Riveting is not as easy. Driving on pavement chunks them out severely

Metal: Not inexpensive. Never had one bend, but tread *seems* to wear faster. Easy to rivet. Tread takes more brunt of pavement. Seem heavier.

Your thoughts?

Re: Wheels: Metal or Plastic?
 

I have thought a great deal about this, and I think plywood is a very suitable material for FRC wheels. Attaching tread is easy, manufacturing is cheap, and the strength to weight ratio is high.

I plan on doing some experiments with this if I have some free time, but I think 188 has used this design successfully in the past for sure. I have a CAD model somewhere which I believe beats most aluminum wheels I have seen for weight.

Re: Wheels: Metal or Plastic?
 

Sounds like you have the trade-offs pretty well figured out Don.

I'd sure like to see more wood wheels....they worked on wagons for centuries...

Re: Wheels: Metal or Plastic?
 

:eek: If it can support a hummer, it can take anything. But honestly the skill to make a good wooden wheel has been lost throughout the ages. Its probably better to pick up some carbon fiber wheels. They are the future:p

Re: Wheels: Metal or Plastic?
 

For one FRC season? You might need a few more than some. Probably 2 for every time you go over the bump and crack a wheel, plus 4/6 for each time you put it in the crate.

Re: Wheels: Metal or Plastic?
 

Now seems as good a point as any to bring this up. What material you should use is a function of what your requirements are. One of these requirements is the way you are loading your material. Another is your strength to weight ratio. Yet another is cost. For most FRC teams what tools you have is also a significant factor. Some teams have the ability to fabricate really nice wheels out of wood/metal that serve their purposes. Others, not so much.

As far as woodworking being a lost skill: http://www.chiefdelphi.com/media/photos/24424 I think not. Never underestimate the skill of an artist working with their preferred medium.

Re: Wheels: Metal or Plastic?
 

:p I guess I have been proven wrong. But it does take significantly more effort and skill to make multiple identical wooden wheels by hand than to make plastic ones (Or you are gonna prove me wrong again, I never made wheels before)

Re: Wheels: Metal or Plastic?
 

we have used custom aluminum wheels for several past challenges and found them to work very well.

Re: Wheels: Metal or Plastic?
 

Who ever said that hand was the only way to cut wood? If we're going to go by hand, then we've got to compare hand-formed wood to hand-formed plastic--and the plastic won't win by much. Making a mold or gouging plastic is going to take a lot of time.

If it came down to a race to build identical wheels, one set from wood, one from plastic, one from metal, and one from carbon fiber, from scratch, I'd go with metal being the fastest, and wood being a close second. In probable order of finishing:

Metal: Depending on the metal, cheap(ish), strong, and can be easily worked with given a lathe, mill, or CNC variant of the aforementioned tools.

Wood: Cheaper than metal, can be strong, and could also be done on a lathe, mill, or CNC variant of those two. Just make sure you have wood bits in when you do, cut it a little bit big, and sand it down the last couple thousandths.

Plastic: Once you have the mold (cheapest way to make a lot of identical wheels) or the CNC program (guess what else can be formed on a CNC?), pretty fast. It's the mold that'll take a while, if you're molding. Reasonably strong.

Carbon fiber: High strength to weight ratio--but low strength to wait ratio in this application. Also rather brittle if you hit it wrong. Great for airplane wing spars, not so much for wheels of any sort, and can take a while to shape and set. Also note the cost... The other wheel types are driving merrily around long before the first wheel comes off the first mold.

We'll assume that everything else is equal for this setup.

Re: Wheels: Metal or Plastic?
 

With the everything being equal...I can machine wood and plastic a LOT faster than aluminum. Maybe because my lathe is small and old, maybe because plastic is a lot softer?

Re: Wheels: Metal or Plastic?
 

Carbon fiber might surprise you with how durable it is. Check out this company that makes CF wheels for cars: http://carbonrev.com/impact_strip.html

Re: Wheels: Metal or Plastic?
 

Using COTS wheels, and keeping the environments in application for each wheel identical, I prefer metal. AM performance wheels are nice in that they are easy to cantilever on live axles and there are only 2 pieces to the wheel.

This thread begs the question: does it matter for omni vs. skid drive trains?

Re: Wheels: Metal or Plastic?
 

We have used all kinds of wheels in the past. For a while we were even making wheels out of lexan, cut on a laser cutter. Had a good grip on carpet but melted with a lot of slip. We have used aluminum with tread (belting)attached also manufactured. The shaft design and implementation changed over the years but it allows us to customize for wheel encoder mounting and bearing implementations. I would stay away from plywood particularly in a game like this past year. The constant stress coming over the bumps would have stressed the laminations and left little slivers of wood all over the field. I would guess that plywood would weigh more than the aluminum version we are currently using.

Re: Wheels: Metal or Plastic?
 

I posted a picture during build season of the wheels we were using this year:

The thread with the picture is here and it has all the information on how we went about fabricating them: http://www.chiefdelphi.com/media/photos/34720

The wheels worked surprisingly well and with a few more tweaks this will be a viable option for us going forward. We may be looking at making a 4 cavity mold so we can pump these out even more quickly. I estimate in one saturday we could have 20+ fully completed wheels done and ready.

As for other wheels I've used in the past, metal (aluminum) has always been our go to wheel because of the stability. We've always made our own wheels so we can control the dimensions that are critical to us and cut down on interfaces (hubs, extra bolts, spacers, etc.)

-Brando

Re: Wheels: Metal or Plastic?
 

Making a wheel out of composites (carbon fiber) just seems excessive and difficult. It's just a wheel, no need to go overboard. Especially considering how the material fails when you drill into it for tread attachment and stuff.

I'd be tempted to use more aluminium wheels, since you would need more material in a plastic wheel to make it as rigid as an aluminium wheel, and I can't think of a time I would want a wheel to be "less rigid". Machining it from solid seems time consuming; I wonder how long it would take to make some with outer "plates" and AL tube though. I think 1625 does something like that.

If I'm buying wheels, AM Plaction wheels are great. The right price point, they worked well this year, tread changing was easy enough, and light enough.