Breakaway question: getting on platform with meccanum?

[RoboMaster]

Originally Posted by EricH

Even that one would have trouble strafing onto the platform, though--for a (best-guess) 14-inch diameter wheel, the roller tips still look to be about 1/2 inch off the ground.

I think you're looking at differently than me. I mean that not only do the maccanum wheels allow you to strafe on the bump, but the rollers would stick out enough that they would catch on the lip of the platform, pull the robot up as they turn, and continue to strafe on the platform. The rollers that are about at the level of the axle would grip on the platform.

Now that I think about it, that might not really work. The catching rollers would have to stick out farther than the others to be the only ones that catch on the lip of the platform. However, it still might work since all the rollers are angled.

[EricH]

Originally Posted by RoboMaster

Now that I think about it, that might not really work. The catching rollers would have to stick out farther than the others to be the only ones that catch on the lip of the platform. However, it still might work since all the rollers are angled.

Which is exactly why it probably wouldn't work. If you were at an angle (and mecanums can move at 45* if they're programmed right), you might be able to get up if the rollers could lock relative to the wheel.

Angle of the rollers won't help if you're going straight sideways. Let's say that they did catch, though, just for the sake of argument. If the platform had a lip (it doesn't), up-going rollers could catch as well as down-going rollers. Bam, you're going nowhere at best, and going onto your top at worst (one wheel locks up solidly). Same argument applies for a flat surface that gets hit broadside by a mecanum--down+up=nothing doing.

The fact that they're rollers doesn't help you much, either; they roll. CG is off the platform, so they'll want to roll off of said platform unless they're locked--at which point you get into either lousy strafing ability or lots of mechanical complexity to lock when you want to climb.

[Chris is me]

Another thing to consider is that the torque of lifting most of the robot's weight off of the tip of the wheels is pretty large - your drivetrain might not be geared to provide that much torque.

[RoboMaster]

Yeah, I see now how it really wouldn't work. Hmmm, well it was an interesting thought.

What I meant by the lip was just the edge/top/corner. Because it's a right angle, as apposed to, say, a vertical plane, it's something that a hook or catch can sort of grab on to. Think of a foot or large omni wheels grabbing onto the edge of the platform by their rollers.

[joek]

you could put a secondary drivetrain that is perpendicular to, and slightly above the mechanums, powered by FP motors, using traction wheels for this sole purpose