Tiny wheel

[sanddrag]

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.

[Tyler2517]

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.

[fox46]

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.

[fox46]

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

[Rob Stehlik]

Originally Posted by fox46

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.

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).

[Joe Ross]

Originally Posted by Mike Marandola

Ah, the tread pattern was worn off. They aren't too small then.

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

[asid61]

Originally Posted by Joe Ross

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

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

[lukedude43]

Originally Posted by Joey Milia

The smallest wheels I've seen used were used on 973's swerve drive in 2012.

192 ran wheels just under 3.5in this year and will most likely be going with 3in for the offseason and next year. 3in is probably as small as we'd go for use on a WCD, might go smaller with a swerve drive though. Small wheels make a huge difference when trying to make the drive gearboxes small and light.

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

[colin340]

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.

[BBray_T1296]

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

[AdamHeard]

2.5" on or 2012 swerve.

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

[JesseK]

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...).

[cadandcookies]

Originally Posted by JesseK

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...).

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

[Tom Ore]

Originally Posted by smistthegreat

I'm pretty sure 525 and 1551 have used some of the ridiculously small Colsons on octacanum pods in the past.

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

[BBray_T1296]

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)