pic: Octocanum Module

[GeeTwo]

Originally Posted by Chris is me

It is simply more robust to put the omni wheel on the pivot and the traciton wheel at the axle.

Again, no argument as stated, but Mecanum ain't Omni.

Originally Posted by Chris is me

First things first, if your solution to a design problem is to drive around the failure mode, that's just plain bad design. You should never have a robot designed in a mechanically weak manner just because the driver "shouldn't" have the robot in that mode when you expect damage. You can't bet your drivetrain on perfect play.

I wasn't so much betting on perfect play, as planning on the play I've seen (which has not included t-boning, for the record). Once T-boning was under consideration based on evidence of others, the defense is straightforward. Training for this situation would be included in driver practice, not left as something that we hope the driver would invent on the spot. In any case, we would design to handle the (externally applied) strafe forces of the worst case we expect to see. If 1/8", there would likely be no pocketing. If 1/4", there would probably still be minimal or no pocketing. As I've stated before: Due to our limited machining capability, our team's general strategy is to select material for our robot, not engineer it.

Our team is not planning for an octanum drive train, but if we did, we'd be at least as likely to have the mecanums as the "fast default" and the traction wheels as the "shifted shoving" state as any of the other three possibilities.

Also, as a final fallback, we'd design any "quad-drop" drive train to have predictable behavior should the modules be pushed by extreme strafe forces. It might involve a drive shaft pushing against a plate with unreasonable friction, but the outcome would still result in a fairly reasonable, predictable outcome.

[Ari423]

So what I'm hearing is either configuration (mecanum or traction wheels pivoting) will have sideways forces that need to be dealt with. For traction, the big problem is T-boning. For mecanum, the problem is the constant force being applied at a 45* angle. Can anyone comment on whether they think both the 1/2" Hex shaft and the 1/8" plates (without pocketing) would be strong enough to stand up to either of these forces?