Lots of good replies. I'm glad I came to this site.
Kerf,
I agree with your opinion on the ball bearings. I see a lot of homemade friction drive systems without any support on the end of the shaft. My leaf blower motor has a shaft about 3 inches long and I have an extra "outboard" ball bearing in a pillow block. You can almost see it in the picture. I'll take better pics after the prototyping phase. The drive wheel is a little closer to the outboard bearing than the motor bearings, so it should receive at least half of the radial forces. It's easily replacable and cost eight dollars at "Farm & Fleece".
There seems to be consensus that slippage will cause more tire wear, and a hard roller should slip less.
Esteban, how are you?
Are you the Schwinnbike member that pointed me to this site? If so, thanks!
It's good to hear that many people with steel rollers are getting acceptable tire life. I've heard about bmx pegs, and if I go with steel, a peg is probably what I will try first (but I don't like their flat profile). BTW, how does that front-wheel-drive work for you? Does it handle OK? No problem with the exhaust noise and fumes in front of you? I can think of a few advantages of having the engine up front.
Loquin,
Are you THE loquin from dbforums and xtremevbtalk? If we have MBs and programming in common, that would be cool. Hopefully you don't share my many less-desirable attributes.
Yeah, everything wears down... even us. The best you can hope for is to minimize the problems. You don't want to be replacing rollers or tires too often. Gotta find the best trade-off. The knurled roller in the pics you posted looked kinda small, didn't it? And did he have bushings instead of bearings? If so, its no wonder they burned out. I'd use bushings in a minute if I thought they would last. You could rig up an inverted oil can to constantly drip on the bushing. You would look like a coal miner by the end of each ride.
Ibdennyak,
People probably make a lot of references about you being from Alaska. So I'll resist the temptation to comment on the Tecumseh snow thrower.
You've been thinking like me (scary) with the caster wheel and pneumatic dolly tire. I figured that the hard rubber on a caster wheel would be similar to tire rubber, and they would be a good match for each other. And an inflatable drive wheel would seem to be the best choice for wear and traction. Like you said, though, even a small pneumatic tire would be too big for direct drive. If I'm going to go through the trouble of gearing the motor down, I would probably want to skip the friction drive and do chain/sprocket. Of course you can do both. That's another thing I might have to try down the road. I think I feel an MB addiction coming on and see a few MBs in my future.
Fetor56,
Love that avatar! I'll respect your authoritah.
That roller looks serious. Ribbed for your tire's pleasure? I think the concave profile is important, too; especially on my skinny-tire setup.
Capturedbyrobots,
It's good to know that someone else is using a skateboard wheel. We can't know what is best if nobody tries it. I can imagine at least one benefit to a rubber roller. If you get a flat, the roller can't damage the edge of your rim. I suppose the pavement still can, though. Speaking of pavement, ibdennyak has an unfair advantage. He's wiping out on ice, so he's going to get more distance on his face plants. The Olympic medal can be made from a golden sprocket.
I'll use up the 4 wheels I have first - wouldn't want to waste a whole seven bucks. That is if it ever gets above freezing here.