[EricH]

It's probably the scrub I mentioned earlier. It's a common 4WD problem. The 2009 slicks are only a little bit slicker than normal wheels on carpet, I'd think. There's quite a few posts on why it happens on CD, including someone calling them Mexican jumping beans.

Good movement off the ground is another classic symptom of the 4WD scrub; it'll act right on the blocks and as soon as it tries to turn on the ground, friction takes over.

Quick sanity check: Are you talking 6" wheels or 8" wheels in the front? The 6" wheels have the truly white surface and are from the 2009 KOP; the 8" wheels came in this year's KOP. There are also 8" plastic wheels that look similar to this year's KOP wheels; I believe they came in the 2010 KOP. The white (and I do mean white) wheels should have the lowest coefficient of friction (and can generate a lot of static).

Here's how I'd start out:

1) Seeing as you already have swivel casters, get them onto the robot right away. Get to the practice field and try driving. Have team members kick the robot to simulate impacts--or have another robot out there do the same. What'll probably happen is that while your turning problems go away, you get a different set, caused by the casters needing to be turned. You'll also lose a little pushing force. There's a physicsy explanation for that; I can give that if you're interested.

If the casters are acceptable, you're done. If not (and I'd be willing to bet that after a match or two, they won't be), on to phase 2, or get ball casters and repeat phase 1.

2) Wrap the front wheels in zip ties all over. Duct tape may also work, but make sure it doesn't stick to the carpet. This is something that you can be doing while you're testing the casters. This should reduce the scrub by giving less friction.

If neither 1 or 2 work, phase 3:

3) Figure out where your CG is. Move the slicker wheels to the middle of the robot, on the opposite side of the CG from the grippier wheels. Put casters on the other end. Whether you drop the middle wheels is up to you; it may be helpful (keeps the casters mostly out of trouble). Pseudo-6WD can help with wheelbase reduction.

Ideally, of course, you find two extra wheels and enough sprockets and chain to build a true 6WD drop-center, but that may be tricky to do fast enough.

Oh, and one other thing: Make room for some carpet on the way back. Inform the FTA that you'd like some field carpet after the regional is done; he'll either point you to the team(s) that have claimed it already or ask, "how much can you take?" Take the carpet home and use it for next year's testing.