Quote:
Originally Posted by Vikesrock
2175 used it this year. Based on their experience I would recommend mounting the center wheel using some sort of suspension unless the floor is perfectly flat. The bumps around the towers would lift the strafe wheel off the ground when it was rigidly mounted.
They used 4 CIMs on the outside wheels and 2 775s to power the strafe wheel.
After coaching 2175 at Champs I have mixed feelings about the drivetrain. Like other omnidirectional drivetrains I would recommend a practice robot or other way to get substantial drive practice in order to take full advantage of the increased maneuverability.
I personally would have preferred a standard 6wd or 8wd setup.
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At the beginning of the season, I also strongly advocated a 6wd drop center. Most people argued that strafing would greatly increase tube placing speed, but I was of the opinion that practice would make tank far superior. We went with the slide drive, in the configuration Kevin described, and I was pretty happy with how it drove after we added that awesome racquet ball to shock mount the strafe wheel. Even on the flat areas of the field, you couldn't guarantee 5 wheel contact (only 3 of which define a plane).
And of course, even with the added strafing that supposedly made tube scoring faster, it was still just as slow because we simply did not practice nearly enough. We could have done some pretty sick stuff with it (which, granted, would have hardly been necessary), but the lack of practice just made it unwieldy in the driver's hands, much like an unfamiliar swerve drive.
I think its definitely better than the typical four wheels in a circle set up, since the forward direction is almost always favored and the strafing is an after thought. It adds a few motors, but it's quite simple to add the fifth to a typical tank drive setup. The amount of practice involved seems to me to be a wash, since for both you just need a lot. The omni wheels do have a surprising amount of traction and you can at least hold your ground, even if you can't push people out of your way. If traction weren't an issue at all, I would probably go with it every time for the maneuverability. But that's hardly the case (unless it's fast enough and your driver is good enough to get around the defence every time).
Our robot's CAD is posted at
http://www.chiefdelphi.com/media/papers/2556 and shows the slide drive configuration. Unfortunately, the awesome racquet ball that we added later in the season was one of those details that slipped through the cracks and didn't make it into the CAD.