Wedgetop vs. Roughtop

[Jared Russell]

To make things more complicated, things like wheel width and diameter have been shown to make a difference in the actual effective "coefficient of friction" you will see when running on carpet (proof that the Coulomb model of friction isn't a great model for tread-on-carpet interactions).

Another consideration is tread wear. Brand new roughtop treads on small diameter, wide wheels really dig into the carpet, but after a couple of competitions, you will probably want to change your tread.

You can buy a selection of tread materials from McMaster-Carr if you do a search for "incline conveyor belting". I would recommend getting a few samples of various materials and you can trade off between traction on carpet, traction on any other field surfaces, and wear. Note that McMaster only sells this belting in 3" width (minimum), so you will need to use a vertical band saw (or similar) to cut them down to wheel size.

[Peter Matteson]

Originally Posted by Jared341

Another consideration is tread wear. Brand new roughtop treads on small diameter, wide wheels really dig into the carpet, but after a couple of competitions, you will probably want to change your tread.

You can buy a selection of tread materials from McMaster-Carr if you do a search for "incline conveyor belting". I would recommend getting a few samples of various materials and you can trade off between traction on carpet, traction on any other field surfaces, and wear. Note that McMaster only sells this belting in 3" width (minimum), so you will need to use a vertical band saw (or similar) to cut them down to wheel size.

This is what we did in 2006 when we switched over to this type of wheel.

If you select and test your tread material properly you will find that there are roughtop materials that will not wear down on a standard carpet playing field all season. I'm not telling what it is, but there is a material that we have used for 6 years on our robots that even using them in continuous demos and driver training has never been replaced.

[GRT808]

If you do end up purchasing the belts from mcmaster carr and end up cutting them I suggest purchasing Blue Nitrile Rough Top belt. Based on previous posts and robots (254,294,973) I've heard it is a very robust material experiencing little wear throughout the season compare to the rough top AM sells. I'm not too sure if using a band saw to cut to size is a good method though (haven't tried it myself yet).

[Cory]

Originally Posted by GRT808

If you do end up purchasing the belts from mcmaster carr and end up cutting them I suggest purchasing Blue Nitrile Rough Top belt. Based on previous posts and robots (254,294,973) I've heard it is a very robust material experiencing little wear throughout the season compare to the rough top AM sells. I'm not too sure if using a band saw to cut to size is a good method though (haven't tried it myself yet).

We've used blue nitrile. I know 233 ran all of 2008 on one set of wheels, but we never experienced the longevity that others did. It certainly didn't wear super fast, but it was not as good as some have advertised.

I would note that you can run the heck out of them and still have tread surface left, but it's basically smooth with dimples in it. We would lose all of our "nubs" and get to this point somewhat frequently.

[Chris is me]

Originally Posted by Cory

I would note that you can run the heck out of them and still have tread surface left, but it's basically smooth with dimples in it. We would lose all of our "nubs" and get to this point somewhat frequently.

Odd, we didn't get to that in our blue nitrile ever. By comparison, our normal roughtop wore "smooth with dimples" shortly after our second competition.

[jwfoss]

Because I am a huge fan of these, have you also considered Colson wheels?

http://www.robotmarketplace.com/prod...on_wheels.html

They have good wear properties, are pretty cheap, and are fairly "grippy" on the carpet as well. Plus I hear that there will be a COTS hub available for the 1.5" wide wheels this year.

[Tristan Lall]

I just found this, which summarizes tests conducted by Brecoflex for their timing belts in robot applications. It includes a chart of "friction" tests on carpet. They quote a coefficient of friction of up to 1.6 on carpet with smooth natural rubber.

Some have had success with using their belts as treads; others (1114/1503/1680 in 2006) haven't. Either way, they're an expensive option and require some dedicated engineering to do right.

[joek]

WELCOME
we find that traction is really not as effective as maneuverability, my team uses mechanum,and we run circles around tank drive teams.

[Grim Tuesday]

Originally Posted by joek

WELCOME
we find that traction is really not as effective as maneuverability, my team uses mechanum,and we run circles around tank drive teams.

And then us tank drive teams push you around.

[Ninja_Bait]

Originally Posted by joek

we find that traction is really not as effective as maneuverability, my team uses mechanum,and we run circles around tank drive teams.

I believe FRC has yet to see a mecanum robot actually driving circles around anything that moves. Video evidence, please!

[sgreco]

Originally Posted by joek

we find that traction is really not as effective as maneuverability, my team uses mechanum,and we run circles around tank drive teams.

I too would like some video evidence.


And just curious, are you trolling?

Around the CD community this is basically verbatim to what is typically regarded as the stereotypical troll post.

[cadandcookies]

Originally Posted by sgreco

And just curious, are you trolling?

Judging by the fact they won Lake Superior this year (traditionally a very defensive regional) I would doubt it.

If you'd like video proof, here's them playing in an exhibition against the winners of the Northern Lights Regional.

http://www.youtube.com/watch?v=efIed7UWGuw

Yes, that is them holding their own against Swartdogs (though I can't remember whether they have octocanum this year, and even if so, what wheels were on the ground) at 1:07. I would say that in my experience, their drive train is quite effective for what they use it for.

Also, they won that match.

Not to derail too much; keep just clarifying that point (if a little late).