Re: Tiny wheel
 

696's WCD in 2013 had 3" Colsons originally. After we couldn't get over the carpet bump,we went to 3.4" custom wheels.

Re: Tiny wheel
 

Were designing a swerve with 2-3 inch wheels right now. It so much easier to get the gearing right. The drive Base is a bit larger, almost on par with west coast. You can definitely support a robot with a aluminum wheel that small. Obstacles could be a problem.

Re: Tiny wheel
 

Just be sure that you bring spares if you are running wheels that small.

All your tread wear will be focussed to a smaller surface area of tread so a 2" wheel's tread will burn off twice as fast as a 4" wheel's and three times faster than a 6" wheel. After seeing photos of some post-competition racing slicks I would shy away from anything smaller than 4" and even then I would be worried.

Re: Tiny wheel
 

You could of course mitigate the wear by going wider but then you're increasing size again.

Re: Tiny wheel
 

Agreed. Rapid tread wear is the main drawback with small wheels. We burned through three sets of 4" wheels last year, and I got tired of changing them (not trivial in a dead axle design).

Re: Tiny wheel
 

They told me that they grind the tread off, purposefully.

Re: Tiny wheel
 

Yeah, I heard that too.
Tread wear. With WCD it shouldn't be as bad to swap out wheels.

I for one would love to see the work of art that a 192 swerve would be.

Re: Tiny wheel
 

as Brian said earlier I have no idea where the small wheel weakness thing is coming from???

In fact I would argue in many cases they are stronger, as side-load has less of the lever effect on the axle interface. In the world of unicycles (spoked wheels) small wheels are often substantially stronger.

When it comes to tread wear I think people need to adapt more NASCAR philosophy. Run the compound that works well for you change it often, if you're going six cim a lot of smart people (610) will argue that traction limited drive is actually the way to go.

Re: Tiny wheel
 

We ran 6 3" colson wheels. After 2 regionals there is no visible loss in diameter or pushing power.

Re: Tiny wheel
 

2.5" on or 2012 swerve.

Smaller wheels don't usually happen because of ground clearance.

Re: Tiny wheel
 

Only thing that hasn't been mentioned thus far is tread wear. Smaller wheels turn more revolutions per distance traveled, thus the tread will wear down faster. Probably not an issue with Colsons.

There may also be something to be said about traction when dealing with non-smoothed treads (i.e. Blue Nitrile or Orange Roughtop). Larger wheels have more contact patch with the carpet fibers vs tiny wheels, thus there are more fibers to push against, meaning increased traction in the forward direction. There is a tradeoff point of where this benefit is removed on very large wheels (> 4"-ish?) However, this is only conjecture based upon findings that 4"x1.5" wide roughtop gets more traction than 4"x1" wide roughtop on FRC carpet (I swear there used to be a whitepaper somewhere...).

Re: Tiny wheel
 

Actually fox46 and Rob both brought that up earlier on this very page. Accelerated tread wear is definitely another drawback to smaller wheels.

Re: Tiny wheel
 

Wow - good memory! Yes, we used 2" Colsons in 2012.

Re: Tiny wheel
 

Larger wheels/more contact patch supplies more grip due to the "cleating" effect where the "pinion" of the wheel has physical exertion on the "rack" that is the carpet. Like gears, there is more than static friction meshing the treaded wheel to the fiberous carpet.

If you were only just calculating straight static friction, wheel diameter and even wheel number has zero effect, because while you are increasing contact surface area, you decrease weight per unit surface area in a 1:1 fashion. All that matters in that calculation is coef of friction and weight of robot (f=mu*N)