66 needs your help!

[KenWittlief]

Im not sure if this will help any - last year we had a large alum plate in the center of the upper part of our robot, that had pneumatic cylinders attached to it - it went all the way across the 'upper frame'

we changed our bot and took that plate off, and I noticed in our next match our bot was swaying back and forth, looked like it was drunk

back in the pitts I realized that plate had been the only source of diagonal rigidity in the upper frame - always gotta have triangles in any square/boxy type of framework to make the structure stiff and strong

BTW - I also noticed the staggering when the bot was turning - and it was also 4WD.

maybe you need to stiffing up your framework - put diagonal cross members, or reinforce the corners with triangles. If you are planning on putting plastic side covers on, that would stiffin the frame up too.

Only other thing I would say is maybe your center of gravity is too high and you have created a Weeble Bot - can you move your battery lower, or put it horizontal? or move anything else down to lower your center of gravity?

but in the end, if the bot looks like its drunk when it turns, does it really matter? If it works, it works - and if you cant fix it your bot will have a unique charactistic that will lend itself to many names that I can think of off the top of my head:

Otis (from the andy griffin show)
Weeble-Bot (weeble wobbles but he dont fall down)
Sir Osis of Liver
Rocky
.....

:c)

[ahecht]

The real key, if using 4 wheel drive, is to have a pair of high traction wheels closest to the center of gravity, and a pair of lot traction wheels on the other side.

For example, you can turn down your skyway wheels on a lathe, one pair just until the first layer of plastic shows, and the other pair 1/8" or so beyond that. Then epoxy and screw a thin strip of incline conveyor belt material (very high friction) to the smaller pair. You should now have two pairs of wheels, about the same size, with vastly different amounts of grip. This solution was used by 992 when I was on it in 2002, and by 190 in 2003 (although we originally had conveyor belting on our front wheels, but it came off in competition). Both bots also had a very short length and a wide wheelbase, which helped.

On the other hand, 190's current robot is very long with a narrow wheelbase, and all our tires our pneumatic. Needless to say, turning won't be a major part of our strategy this year.

[Dick Linn]

Last season, we used 2 of the pneumatic Skyway wheels on one end, then a pair of the poly wheels on the other (8.75 or so inch diameter). Since the poly wheels were not the exact diameter of the rubber wheels, we "turned them down" by holding them between our knees and using a belt sander and a bit of elbow grease (not to mention finesse) to get them even and slightly radiused in the axial direction. Talk about a mess of black dust! Glad we did it at my employer's shop and not at school

Because we were climbing a steel mesh that year, we re-grooved the original channels across the tire using a 1/4 inch rat-tail wood file. The result was a bot that could climb the wire ramp (with a 110 lb. person on board) but still manage to turn, since the poly wheels were just a bit more slippery than the rubber ones. The axial grooves bit into the mesh on the way up to provide traction. This year the best way depends on your method of attacking the platform and whether or not you see it as a pushing/pulling contest.

As to turning and handling, you either play around with the geometry, center of gravity and traction, or gear it down to be a real brute to get the desired results. Adjusting for handling can be both a science and an art. At this point in the build, I think it depends on how much time you have left. Quickly try it on a different surface to see if things change dramatically. You might discover something.

[KenWittlief]

we "turned them down" by holding them between our knees and using a belt sander...

if I saw you doing that I would have spleened you with a spork!