Re: Caster Wheels
 

Use AM Plastic omnis if possible. Coolie Dualies are wheels I've never seen used successfully, unfortunately.

Re: Caster Wheels
 

What about ball caster, how well do they work?
If they don't really work i think we probably just go with a 6 wheel drive system.

Re: Caster Wheels
 

They can work. They're better than swivel casters. That just isn't saying much, though.

Honestly, skid pads would work quite well to replace casters, if it weren't for the bumps in the floor. (Though that could be dealt with--see if you can get a look at 1266's rookie robot.)

FYI, I don't know of a single problem with 330's omnis last year, and they took a heavy pounding. AM plastics, I want to say 8", dual configuration.

The trick with omni wheels is to put two wheels per wheel, placed so that the rollers on one wheel fill in the between-roller gaps on the other wheel (the dual configuration I mentioned above). It provides a smoother ride, reducing wear and tear on the wheel overall.

Re: Caster Wheels
 

Why would skid pads work better than ball casters? They have much more friction. Do you have experience with either you're basing this on?

Re: Caster Wheels
 

I'm also thoroughly confused...


Also, not to be a downer...it is week..4(?) now. You might want to get a move on things if you are still deciding on your drivetrain this far into build.

Re: Caster Wheels
 

Skid pads, done right, can be quite fluid on an FRC field. 330 did small plastic skid pads back in 1998, on the four corners of a 2WD. Yes, my memory does reach that far back! (I just don't remember if they had drive problems--I remember the full-robot failure, and I think that was the year they were 20+ lbs over, with a not-well-designed arm.) 1266's rookie robot, from 2004, had 2WD with two rather good-sized skids of aluminum (least I don't think it was steel) with an HDPE (?) floor contact pad. They didn't have a whole lot of trouble maneuvering, IIRC. They climbed the step OK with the skids, until the HDPE decided it wanted away from the Al and tried pulling out.

Ball casters may have less friction, but if they do go haywire, look out, and the CIMs can beat that friction fairly well.

Re: Caster Wheels
 

But if a ball caster "breaks" and gets stuck, doesn't it just become a skid pad?

Re: Caster Wheels
 

Ball casters can also be problematic.

Best practice says if it touches the floor it should be driven. A ball caster slightly lifted off of the floor by under floor structures like the pole support can unload one of your drive wheels and make control very difficult.

Can plastic omni wheels break, yes but so can any other wheel when abused. AndyMark changed the amount of reinforcing fiber in their omni wheels after their first year and made them stronger. We have used these wheels for every year since their introduction (except for Lunacy) without a single failure. This includes last year where they were slammed into the humps in the field over and over again.

If you are still concerned about them breaking, double them up (as shown on their web site) and get twice the traction and redundancy.