Why such large wheels?

[sanddrag]

Why do teams use such large wheels? Especially when they still make their ground clearance so low. It takes more space, weight, and gearing. If your wheels are large, do you have a good reason?

[Peter Matteson]

What do you consider large?

We typically use 6" or 8" wheels mostly because we bought a lot of them and they are in the shop. This year we went to 4" for our design because they were the right choice for our design.

[Bill_Hancoc]

8in
they come with the kit

if done right big wheels can look really cool, not in a "spinners and chrome" way but kind of a tuff look

[lukevanoort]

We're using 8" kit wheels not because of a desire for big wheels, but because we have seventeen cents in our team account (and a new drivetrain head). (but a budget of $1000... interesting math) Anyway, my point is, the bigger wheeled teams might do it for budget, or happen to have them lying around. Or, they could want a solution to speeding up their robot without gears. In previous years we used bigger wheels because we had had sucess with them. As a matter of fact or '03-'05 robots used the same wheels with minor tread pattern differences.

[Chriszuma]

Well i think the concept is that they will have more surface contact with a wider radius of wheel. In practice, I'm not sure if this works. We went with about 6" diameter, 1.5" wide wheels and they gave us enough traction to push around whoever we wanted (except two teams, sadly)

[s_forbes]

We went with 8" wheels for the reason you first stated; we need the clearance.

Had it been a different game, I would have wanted to go with smaller wheels, maybe 4". This leaves more room for other things on the robot chassis, and there really isn't any reason I can think of to use larger wheels if you don't need to clear a ramp.

[greencactus3]

bigger wheels=less rpms. so the bearings dont take as much abuse when its not a perfectly straight axle. and also a larger sprocket can be mounted.. in general a larger sprocket is harder to derail chains from.

[Billfred]

This year, 1293 is going with 8" Skyways on the outer four wheels, and IFI wheels in the middle of our 6WD setup. A big reason for this is cost and lack of need--six roughtopped wheels from IFI, doubled for a practice robot, would be quite expensive. Since we seem to be driving around just fine with our current arrangement, with no noticeable wheelspin even on our slick tile floor, we're sticking with it.

On a side note, these are actually the lightest wheels we've ever used on a robot. On Bob, we used the 12.5" pneumatic Skyways that came in the kit. Last year, we had these big heavy 8"x2" wheels that, ignoring cockroaches, would be the only things to survive a nuclear blast. Staying with lighter wheels this year is a change for us, but I think it's definitely working for the better.

[Mike Schroeder]

team 25 uses 9x3 skyway wheels, why? cause it works for us we swear by them

team 1923 is using 6 8in skyways 2 in the front and 4 in the back again why? cause it worked for them

its all a matter of taste

[team222badbrad]

Why such small wheels?

Ours are 8.5'' in Diameter, who can guess what kind of traction material we have?

[dtengineering]

This is our third year. Each year we have used smaller wheels. Our first ones were monster 12" x 2" pneumatics in a 4x4 arrangment. That was done so we could climb up the 6" step.

Last year we used 8" wheels in a 4x4 arrangement with pneumatically actuated caster wheels to help with turning. That was done so we could drive over the bottom edge of the goals if we needed to (as it turned out, it would have been better if we couldn't).

This year we are down to 6"x1.5" wheels in a 6x6 arrangment.... just enough to get up the ramp.

There are many advantages to the smaller wheels, namely reduced weight and size, but also that because the radius is reduced you can put the contact point of the wheel closer to the outside of the robot, thus improving your front/back stability. The bigger wheels are better for climbing over obstacles and for ground clearance. The big wheels from our first year also gave the robot a very rugged "Moon Buggy" type look. Aesthetically it is still my favorite of our three robots, but, well... it didn't really perform all that well.

Next year we are just going to put a few skyhooks on and let it hover.

Jason

[sanddrag]

Originally Posted by dtengineering

This year we are down to 6"x1.5" wheels in a 6x6 arrangment.... just enough to get up the ramp.

We believe 3.375" is just enough to get up.

[sanddrag]

After seeing the regionals, I think it's time to revisit this.

Why are all your wheels so big? We get up the ramp just fine with 1 inch wide 3.3" diamter wheels (6 of them) and 3/4" of ground clearance under our side frame rails and about 3/16" clearance under our gearboxes.

Your wheels do not need to be big. Your ground clearance does not need to be high. You are causing more trouble for yourselves. I'm sure in some cases, there is a darn good reason for it that the team thought very hard about, but in most cases I've seen, I ask and they say "oh, smaller wheels, hrrm, never thought of that"

[meaubry]

We use 12 inch pnuematic wheels - 3 per side. The reason is three fold - they are grippy for climbing, a completed purchased assembly that we have little work to do to modify for use, and best of all they cost about $7 per wheel including the bearing.

We used them over the past 4 years, and have gotten used to them and like them alot.

[TimCraig]

Finding wheel/tire combinations with the right width is what drives our selection process. Since we went to two wheel drive for control issues, we also can go for maximum traction, hence very wide wheels.