[flameout]

Originally Posted by PAR_WIG1350

Either lay out something to cover the ground

Unfortunately, this is not possible.

cover the individual rollers with a sleeve of some sort ... likely be time consuming and trying to keep the roller covers in place would be challenging

This is something I have thought of... however, the rollers are closely spaced IIRC, so we'd need to grind them down first, but I think it'd be doable. However, coming up with a suitable cover seems like the hard part... any ideas?

performance might be affected.

Performance is not very important, although reliability is.

2) have a different set of more durable rollers for driving on rough ground
Skateboard wheels come to mind, put 2 or three on an axle and shape them to the approximate contour of the mecanum rollers (the sponsors with machining capabilities might be able to help). Just switch the rollers when you switch surfaces.

Switching the rollers would be quite time-consuming, but I don't see us doing it more than a few times per year, so it's plausible. This would make dealing with gym floors easy -- we'd only switch for the duration of our presentations (the rest of the time we'd use our low-wear wheels).

I'm not familiar with skateboard wheels, but I'm worried that they might not have enough traction. Although we don't need a lot of traction, I think the kinematics of a mecanum drivetrain break down when the wheel isn't significantly more difficult to skid than it is to roll.

3) instead of replacing the rollers, maybe new rollers could be cast over the old ones
This saves money on urethane, but the layered structure might fail, which wouldn't be good

That's something I haven't really thought about... good idea.

4) this one is like number three, but the rollers are cast over PVC cores, this allows for more control over the structure of the wheel so that the rollers are more uniform, every time the rollers wear out, remove the remaining tread and cast a new one over the core.

That does sound like it would work.

Also, I don't see why we need to use urethane. Is there anything less expensive that would still do the job? I think I recall something a while back about casting holiday ornaments out of hot glue. What do you think about this idea?

EDIT:
Earlier I mentioned a concern about dirt -- it is possible to avoid traveling through the dirt (just a minor inconvenience). Therefore, in my opinion, it comes down to our ability to cheaply repair/replace the rollers.