Where can we find good pneumatic wheels?

[Chris is me]

Originally Posted by EricH

Oh, and using 6 of these wheels on a 6WD is asking for turning problems, even with a dropped center wheel.

Tell that to 70, 494, 469, 1114, and 2370 last year. 2370 actually used four pneumatic wheels in the long configuration - and turned just fine, somehow! I'll never understand that.

[EricH]

Chris, I said 6 of those wheels in a 6WD drop, in 2006. We had trouble turning. I don't know if there is any video of the Arizona practice rounds around, but we bounced around a bit.

Solution: the front wheels, which were the primary off-ground wheels (6WD drop drives rock a bit, but can be weighted so one set or the other is mainly on the ground), were replaced with 6" Skyways. No more problems. In 2005 we used 6" Skyways on the corners; in 2007 we broke quite a few AM hubs on our rear wheels, but not so many on the front wheels. (We also caught a hub that had partially failed. Mark Koors happened to be the FTA at the event, so he got a wheel in the process of failing for analysis.) 2008 saw the revised AM 6" wheels on the corners.

[ChrisH]

Originally Posted by topgun

What kind of turning problems? Slow, or bumping, or fuse blowing?

Or are you saying you don't use 6 of these wheels on a 6WD?

How do you overcome the turning problems?

Major bumping, several inches in the air bumping. Pneumatic tires bounce really well once you get them started, and if you keep going they bounce higher. If we're using 6 wheel drive we'll probably have plaction wheels on the corners. They slide sideways pretty well without giving up much in the way of fore-aft traction.

[Yalib]

Can enyone help us compare the wheels that were given above with some advanteges and disadvanteges about each? i have to say the mbs wheels looks really high quality...

[EricH]

The McMaster ones are high-traction. Give us 2 of those as our center wheels, and we'll able to hold our own in a pushing match if needed. 4, and we'rr a bit better. They wear well, too; when you see the red, pull out the spares, but you've got a few more matches. One set could last an entire event, eliminations included, and be usable in practice later. The cost is about the same, $20 US/wheel, but McMaster is known for fast shipping if they're near your area (and willing to deal with you).

I don't know about the MBS wheels in terms of traction and wear; mountainboards aren't exactly designed for light use, though. (And they're not designed to be self-powered...)

Looking at the Radio Flyer wheels, they're more expensive (over $25/wheel) than either of the other two. Again, no real experience there.

The biggest problem with all of them is that they will need modification to work with a drive system. A sprocket needs to be attached somehow. See the explanations earlier in the thread.

If it's track record you want, McMaster wheels have a lot of regional and Championship wins, and I don't know of a single failure other than tread wear, which everybody has. I don't know about the other types mentioned.

[akoscielski3]

Originally Posted by Joe Ross

50% of the time that 330 used mcmaster 2717T51, we went to Einstein. Your mileage may vary.

Can someone post a link to these wheels, I can't find them at all!

Thankss

[akoscielski3]

Originally Posted by ChrisH

Major bumping, several inches in the air bumping. Pneumatic tires bounce really well once you get them started, and if you keep going they bounce higher. If we're using 6 wheel drive we'll probably have plaction wheels on the corners. They slide sideways pretty well without giving up much in the way of fore-aft traction.

If everyone was havng problems with 6WD why was 1114 moving so easily with 8WD (2010).

[AustinSchuh]

Originally Posted by akoscielski3

If everyone was havng problems with 6WD why was 1114 moving so easily with 8WD (2010).

I would be very surprised if 1114 had all 8 wheels in the same plane. I bet that the center four wheels were dropped slightly, on the order of 1/8".

[EricH]

Originally Posted by AustinSchuh

I would be very surprised if 1114 had all 8 wheels in the same plane. I bet that the center four wheels were dropped slightly, on the order of 1/8".

And that made the wheelbase shorter than ours in 2006, where we had very little drop and 6 wheels. Long wheelbase=tougher turning, in general. This is why most 6WD robots have a dropped center wheel or omnis (or other low-friction wheels) on the corners. We didn't have nearly as much trouble after putting Skyways on the front corners.

Link to the McMaster wheels: go to the McMaster site and enter the part number into the search box. You'll get the page; the wheels are near the bottom. We used the gray treaded ones.

[Wayne TenBrink]

We haven't used pneumatic wheels, but are thinking about it. We purchased two different 6" x 2" caster wheels from Grainger, p/n 1ZPE1 and 2RZJ3. We like the 1ZPE1 the best. It has a stronger hub and stickier, softer tire. Neither have great bearings. Each cost around $26.

Does anybody have experience with either of these, or know how they compare to the McMaster Carr 2717T51?

[Chris is me]

Originally Posted by EricH

I don't know about the MBS wheels in terms of traction and wear; mountainboards aren't exactly designed for light use, though. (And they're not designed to be self-powered...)

For what it's worth, neither are the McMaster wheels... They're for casters, no?

Mountain board wheels are high traction, but that's partly because they're designed for dirt and grass. Thus the wheels are pneumatic to increase their contact patch, since on loose non-carpet surfaces your surface area comes into play (dynamic friction due to deforming surface). So how they perform on carpet remains to be seen.

Do keep in mind traction for non driven wheels may not be the #1 priority. Scooter and inline racing wheels are a perfect size for first (90-125mm) but have a polyurethane tread with a hard 80-95A durometer to decrease wear and to allow for controlled skids.

[EricH]

Originally Posted by Chris is me

For what it's worth, neither are the McMaster wheels... They're for casters, no?

True. Radio Flyer wheels have the same problem.

[Karthik]

Originally Posted by akoscielski3

If everyone was havng problems with 6WD why was 1114 moving so easily with 8WD (2010).

There's considerably less "bounce" in the 8WD we had compared to the 6WD that 330 employed with the same wheels. If construct a polygon between the centres of our wheels this year (or any standard 8WD) so get an upside down trapezoid. If you do the same with a 6WD you get a triangle resting on a vertex. Looking at these shapes, it's easy to see why one would have more rock, and thus more bounce.

Originally Posted by AustinSchuh

I would be very surprised if 1114 had all 8 wheels in the same plane. I bet that the center four wheels were dropped slightly, on the order of 1/8".

Austin is correct. Here's a picture where our drop is depicted pretty clearly.

http://www.simbotics.org/resources/g...l/_3260103.jpg

[EricH]

Wasn't just the rock, though. It was, literally, the bounce--the effect of high-traction wheels trying to turn. Same problem that caused someone to compare 4WD systems to Mexican jumping beans. Only, it was on a 6WD drop center. Lower traction at one end resulted in just the rock, and that's an issue that's easy to design around. The next two years, it was McMasters in the center and AndyMarks on the corners.

[Chris is me]

I bet that depends largely on how inflated the wheels are. If you look at 1114's wheels, they're rather full-looking, so they probably are less likely to "dig in" while sliding and get stuck, causing stored / released energy in the form of bouncing.