Highest traction wheels

[MichaelBick]

Originally Posted by cbale2000

That is the key point in this question. Given that you're looking for traction on a smooth surface, rather than on carpet (which most teams are more used to dealing with) I can't give you a definitive answer, for that matter, there may be some debate on whether or not there is one, but that said I'll try my best.

There's really two things you want to be looking for to answer this question: Contact point surface area, and material types.


On a smooth surface, wheels with more surface area in contact with the surface (IE, a smooth wheel like a Colson wheel) should have better grip than one with less surface area in contact with the floor (like a Plaction wheel).

That said, material type is important too. As we saw in years past, if you put plastic wheels on a plastic floor, the result is very little traction. Taking that into consideration you may find that wheels with certain kinds of rubber (or other gripping material) grip better than others. I've not personally played around with Colson wheels on a smooth floor, but I do know that AM's HiGrip wheels have an extremely grippy rubber surface, meaning they may actually grip better even though they have less surface area in contact with the floor.

Of course if you REALLY want to grip the floor, there's simply no substitute for Tank Treads.



Disclaimer:
I don't claim to be an expert on traction, and I'm sure someone more knowledgeable will explain it better, these suggestions are based on my own personal observations over the past 8-ish years.

I believe some of your statements are incorrect. Usually, the only variables that affect traction are coefficient of friction and weight. Because wider wheels just mean that the same weight is spread over a larger area, you have the same amount of traction. This is different when roughtop tread and carpet interact, because the roughtop "locks" in witht he carpet and increses the amount of traction you have with wider wheels. This is also like drag racing, where they heat up the wheels so that they "stick" to the ground and wider wheels have more traction.

To answer the OP's question, I have heard that colsons have the most traction on flat surfaces.

[Jeffy]

Originally Posted by MICHAELABICK

This is also like drag racing, where they heat up the wheels so that they "stick" to the ground and wider wheels have more traction.

This is also in effect on robots. The wheel will heat up during use and can gain traction because of this.


As stated above, softer wheels will do you better most of the time. However, when I built bots that drove on painted wood surfaces or stainless steel surfaces, a very soft foam wheel often had less traction than a harder rubber wheel.

One more thing,
When running a robot on a hard surface, the surface quality effects traction much more than on carpet. Sticky wheels will suck up dust and their CoF will quickly change.

If this were my project, I would first try a few different types of urethane wheels and test to see if I liked the results. I would also try a few different tread patterns.

[mman1506]

RC carpet racers use foam wheels on carpet. Porous foam tends to grip really well on carpet but it would be impratical for frc use because of how quickly it wears

[Michael Hill]

Originally Posted by MICHAELABICK

I believe some of your statements are incorrect. Usually, the only variables that affect traction are coefficient of friction and weight. Because wider wheels just mean that the same weight is spread over a larger area, you have the same amount of traction. This is different when roughtop tread and carpet interact, because the roughtop "locks" in witht he carpet and increses the amount of traction you have with wider wheels. This is also like drag racing, where they heat up the wheels so that they "stick" to the ground and wider wheels have more traction.

To answer the OP's question, I have heard that colsons have the most traction on flat surfaces.

I think there are a couple of misconceptions here. There contact area will actually not be increased by that much with a wider wheel. It sounds odd, but the pressure that would be applied over a thinner wheel is now spread out over a wider one. That lower pressure doesn't allow the tread to expand as much along the wheel. However, because your width is greater, the contact area is roughly the same.

Second, drag racers have wide tires solely because of heat. You need big tires to dissipate it all. The stickyness that happens does, in fact, increase traction because it now brings in adhesion (your coefficient of friction is now >1). It literally is pulling the car down when this happens. However, in our situation, our wheels aren't producing near enough heat to do any of that.

Another thing to remember is that friction is very inexact. It's been seen in some circumstances that the coefficient of friction can change with respect to load (which goes against classical friction theory). There may be many other factors that come in to play as well.

[Mark Sheridan]

Originally Posted by Michael Hill

I think there are a couple of misconceptions here. There contact area will actually not be increased by that much with a wider wheel. It sounds odd, but the pressure that would be applied over a thinner wheel is now spread out over a wider one. That lower pressure doesn't allow the tread to expand as much along the wheel. However, because your width is greater, the contact area is roughly the same.

Second, drag racers have wide tires solely because of heat. You need big tires to dissipate it all. The stickyness that happens does, in fact, increase traction because it now brings in adhesion (your coefficient of friction is now >1). It literally is pulling the car down when this happens. However, in our situation, our wheels aren't producing near enough heat to do any of that.

Another thing to remember is that friction is very inexact. It's been seen in some circumstances that the coefficient of friction can change with respect to load (which goes against classical friction theory). There may be many other factors that come in to play as well.

In pneumatic tires or equivalent, this is true. Widening the tire will not change the contact patch, the patch will grow wider but shorter. Thus the way to increase the contact patch is to make the wheel a bigger diameter. I need to dig around to find the book I referenced this from.

However, for solid wheels I do not think this is totally true. I think it behaves more like a rack and pinion. I think the contact patch is small, so to make it bigger is to make the wheel wider. As with gears, you can't make more teeth mesh, but you can make the teeth wider to hold more load (assuming the DP is constant). If your "teeth" on your wheel can hold more load, you have more traction. Of course this can't be totally true because the wheels sink in the carpet a bit.

[Clem1640]

We've done some static friction coefficient testing on both carpet and polycarbonate surfaces and found that the HiGrip wheels are excellent. We, however, did not test Colsons (even though we used them last year) or Versa wheels (yet - we have purchased a set for testing).

We test on two axes: the in-drive direction and perpendicular to this.

I agree that friction coefficient (between the wheel and driven surface) and the normal force applied between these two surfaces (generally the robot weight) are the key factors in determining traction.

[pfreivald]

Anecdotal evidence from this past season indicates that Colson wheels to not grip as well as wedge top on carpet, but are absolute beasts on smooth surfaces...

...rattin' smattin' octocanum redesign...

So on a related note, what's the smallest wheel you can find (say, 2" diameter) with excellent carpet grip?

[Boe]

Originally Posted by pfreivald

So on a related note, what's the smallest wheel you can find (say, 2" diameter) with excellent carpet grip?

A custom wheel with tread of your choice i prefer mcmasters blue nitrile tread personally

[pfreivald]

Originally Posted by Boe

A custom wheel with tread of your choice i prefer mcmasters blue nitrile tread personally

Cool. Do you have a part number?

[Boe]

can't tell if your making a comment about the custom wheel part number or asking for the tread part number, but either way the tread part number 5994K852

[pfreivald]

Originally Posted by Boe

can't tell if your making a comment about the custom wheel part number or asking for the tread part number, but either way the tread part number 5994K852

Tread! Thanks!

[Boe]

no problem its worked good for us for the last two years. Last years bots tread finaly started to show significant wear after the season during demos while we were driving on pavement and concrete

[smistthegreat]

I've heard good things about cutting tread into Colsons like so: http://www.team228.org/gallery/125/b...3511-8f172.jpg

I have no concrete evidence that this increases traction, but I know 228, 125, and I think 1477 all cut their tread like this so perhaps someone from one of those teams can chime in here with some data.

In response to Pat's questions about extremely small traction wheels, the only COTS ones I can think of are Colsons and Banebots, and even the hardest (blue) Banebots wheels would have to be changed too often to be worth it. I would at least explore the possibility of cutting treads into Colsons, because the alternatives are machining intensive.

[pfreivald]

Originally Posted by smistthegreat

I've heard good things about cutting tread into Colsons like so: http://www.team228.org/gallery/125/b...3511-8f172.jpg

Cool -- that's easy to do, and the Colsons we're using are cheap enough to ruin without feeling bad about it!

[AlexH]

Originally Posted by pfreivald

So on a related note, what's the smallest wheel you can find (say, 2" diameter) with excellent carpet grip?

http://teamwhyachi.com/wheels.htm

45a tread. 2.25" dia

priced in the lol price range at $41


you could also modify a pulley like mcmaster part #6235K72 to work as a wheel.