Re: PVC to wood bearings??
 

Also, concerning brushes, we used a 23" diameter outer helix combined with and offset by 180 degree inner spiral that about 12" in diameter and a piece of 2.5" PVC in the middle spinning on a CIM attached to an old BaneBots transmission. This was quite enough to get the ball up our four revolutions to the top (about 4') using no traction tape or brushes, just slick PVC against the orbit balls. I should add that we lost our single sad orbit ball on Saturday so we had to use a basketball stand-in for some of our testing. The diameters are the same but the basketball is much much heavier than the orbit ball and our setup was still enough to move the much heavier ball up our helix. Granted the basketball is much stickier than the orbit ball but it's weight should be enough to offset any benefits top be had by it being stickier.

Re: PVC to wood bearings??
 

We're using ABS (black plastic sewer pipe) for our rollers, and we have a wood robot they are mounted to. They are mostly all chain driven.

We discovered that the 3" ABS caps that some stores sell are flat on the ends, and also they are a pretty close fit to the inside of 4" ABS pipe, as well as to the outside of 3" abs pipe, so the 3" caps can be used for two different sized rollers.

There is a neat thing called a "flanged radial ball bearing", and it can be used in a chain sprocket, or put into a hole drilled in that ABS end cap. When the bearing is supported on the end of a bolt, then you have a complete roller, and it's pretty easy to make it driven by a motor/transmission by #35 chain (same as the drive wheels use).



this is the cap with a sprocket installed, and an FR8ZZ bearing installed. This is the type of sprocket that came in the kit, and it needs to have the hole slightly enlarged (a half round file will work) to make the bearing fit. You can drill the 1-1/8" hole in the cap with a "Forstner Bit", and it should give a good fit for the bearing in the end cap for the other end of the roller.

Re: PVC to wood bearings??
 

I think everyone answered your question. But may I suggest using like poly ethylene or some other plastic instead of copper for the out side? depending on how much copper, you might be raising your center of mass unnessarily by putting on too much weight. Make sure to cut plenty of holes in the outside too. :)