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#1
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Highest traction wheels
Out of AM's HiGrip, Plaction, and Pneumatic Wheels, and these Colson wheels I've heard about. What definitively has the highest traction (on "smoother" surfaces)?
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#2
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Re: Highest traction wheels
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. Last edited by cbale2000 : 08-05-2013 at 02:47. |
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#3
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Re: Highest traction wheels
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To answer the OP's question, I have heard that colsons have the most traction on flat surfaces. |
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#4
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Re: Highest traction wheels
Please elaborate on "smoother" surface.
Last year we found that there was a dramatic difference on the polycarbonate between the various wheel types. The Hi-Grip, when clean had a lot of traction where-as wedge top (usually a pretty good choisce for carpet) was quite poor. Colsons were nice in that they had the least change (for us) surface to surface. If you are not worried about durability, in general the softer the durometer, the grippier the wheel. There are also some really neat compounds out there that have exceptionally good grip. |
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#5
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Re: Highest traction wheels
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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. |
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#6
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Re: Highest traction wheels
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
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#7
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Re: Highest traction wheels
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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. |
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#8
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Re: Highest traction wheels
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You know, testing this on an actual robot would be an excellent summer project... |
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#9
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Re: Highest traction wheels
I've actually heard that Vexpro Versa Wheels have the most traction on FRC carpet. I have not used them and can't back this up. I think that 2337 did this year, maybe someone will read this and correct me?
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#10
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Re: Highest traction wheels
They have good grip in the forward axis due to the "W" pattern, but horrendous grip in the sideways axis. This was confirmed for experimentally for us at Championships. (It wasn't our robot, mind you.)
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#11
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Re: Highest traction wheels
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.We did have diffuculties with being pushed sidealong with the VexPro tread on 8-inch wheels in a 6-wheel configuration. |
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#12
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Re: Highest traction wheels
Hm.... that lack of lateral grip might make Versa wheels a great choice for the outer 4 wheels in an 8 wheel tank drive.
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#13
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Re: Highest traction wheels
I would personally prefer drop-center or omnis. They have some grip, enough to interfere with turning if you were to use them like omnis, but not enough to stop a robot with even a weak drivetrain to push you sideways into a wall with ease.
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#14
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Re: Highest traction wheels
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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. |
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#15
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Re: Highest traction wheels
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. |
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