[EricH]

I believe a 4WD high-traction drivetrain has been compared to a Mexican jumping bean. You WILL bounce when turning, if your drivetrain is significantly longer than it is wide! (Unless you're from FRC 25.) Even some 6WD high-traction drivetrains with dropped center wheels have had that problem.


That said, a shifting gearbox will accomplish most of what you're looking for. However, 4 of them is going to be a bit on the heavy side, so you want to find some really light ones. Orchestrating the shifting would depend on what you used; servos would be as simple as a trio of Y cables to split one output into 2, then each of those into another 2, while pneumatics could be done off of one solenoid by splitting up tubing runs (though I might suggest 2 solenoids with the equivalent of a Y cable).

The other "problem" is that you'll probably want to use higher reduction than most teams use in their boxes, due to not having any chain/belt to knock it down a bit farther.

If you have the funding, I'd spend the money on a couple of AndyMark or VexPro shifting gearboxes and spend some time tinkering with them to find out exactly how they work, rather than making the gearbox from scratch on the first iteration. (Later iterations, go for it. But if you've never done shifting, learn from the masters.)

BaneBots to CIMs, don't do it. Not because it can't be done, but because when you stall the drivetrain (never "if", in FRC), you'll probably be replacing the BaneBots due to magic smoke release--they don't handle stalling well. MiniCIMs or BAG motors would be a better choice in terms of durability. You'll need to match up the motors to get the power/speed you want.


I would suggest looking into the West Coast Drive--typically 6WD, dropped center wheel (eliminates the bouncing problem) directly driven off the single gearbox for each side, all other wheels chained. Or the Kitbot on Steroids that 1114 has been spreading. Adapting one of those to fit your preferences might be a little easier than going completely from scratch.