Cheap and Easy Drive Roller

Needing a drive roller for my last build, I began to look for something I could build "in house" easily. Looked at all kinds of things but came up with this, a rubber roller. It can be made in any size you have a hole saw for, just start with a saw 1/8" bigger than the roller size you want. Ebay is an excellent source for sheet rubber, I was about to buy a 1/2" thick sheet when I remembered I had a scrap of horse stall mat from Tractor Supply I had cut to fit my truck bed. It is 3/4" thick so three discs were needed for the 2.125 tires on my bike. I quickly hole sawed 3 discs. Since there were going on a 5/8" crankshaft I then drilled them to 5/8 with a blade type wood bit. Just drill to whatever crank size you are using. The drill leaves the rubber undersized some what, so the fit on the crank is very tight. I obtained 4) 9/16" flat washers from Ace. The hole in them is exactly 5/8. These are used as back-ups/spacers. I also bought a 5/8 clutch collar while at Ace. This fit over the end of the crank and travels inward as the bolt is tightened to compress the discs. Thats it! the crank rotation tries to tighten the bolt so you never have to worry about it coming loose. This set up fits a standard industrial type engines 2.5" long crank. There is just barely enough crank with this size roller to engage the washer and clutch collar. With narrower tires not as many discs will be needed and probably more washers to get the discs centered over the tire. Once set up a replacement roller can be made in 5-10min. So far I have about 65mi on the roller, and it still measures it original 2" diameter, and that includes some riding on sand/gravel. The disc with the small hole has not been drilled to crank size to show the difference.

Thanks deacon! I had thought about wood too. I have some 3/4 oak laying around, might give it a shot. Whats good about the rubber though is it compresses forcing it to grip the crankshaft and drive washers.

I am thinking the white plastic cutting boards at Walmart would work if its not too slick, its certainly tough enough. Grooves could easliy be cut into a roller made from it to improve traction. On non compressible materials, if the clutch collar had a keyway and the outer washer was brazed to it then it would be a positive driver. A pin of sorts through the washer would positively drive the roller. Keying the roller itself may split certain materials under load. The rubber is the simplest to make and so far is holding up great. I have no idea how hard the rubber I am using is, its probably soft being a cushion for horses. On ebay the sheet sellers list the durometer hardness of the rubber, so you can choose the hardness. I think I will make an oak roller just to experiment with, seems the development of the bike itself is finialized. Think I will just run it under compression. However I am pertty positive it would drive if bonded to the outer washer with silicone adhesive.

Thanks Ron. No it has never spun. The fact that the drills leave the shaft hole slightly undersized, plus the pulldown with the crank bolt on to the washers positively locks it. The beauty of it is that you can make a roller of any size for a shaft of any size. The Lawnmower shafts are commonly 7/8, thought some are 1". The 7/8 is more difficult to find stuff for, this approach would make it easy. I now have about 250+mi on the original roller, has very little wear, tire also. Will try to post a pic.

Heres a pic of the 250+mi roller, about all that has happened is it has formed itself to the tire contour, still basically the same size it started. It dusted for the firsrt few miles then pretty much stopped. I believe it has work hardened. Absolutely unfazed by a gravel road. Road one a mile in and out to a friends this weekend. Looks like a long haul roller.

Hey Ron, there is a thread under "Lifan 2.5hp friction drive" in DIY that has the build pics.

Next installment on the cheap and easy theme. Oak rollers. I know these have been used for years, but I have never tried one and I like it! I imagine any wood of a harder nature could be used, like Southern yellow pine. They are real easy to make, just hole saw em with a saw that is an 1/8" bigger than you want. I counter sunk the outer side to allow the clutch collar to recess into the roller. There is a piece of 1/4" rubber on the inside up against a washer(s). This allows the roller to compress against it and provides the drive. I Gorilla glued the roller halves together right on the engine, just put em on with the glue and tighten em up. I can change a roller in under a minute, which allows quick ratio changes. Plan to carry different ones in the bike bag. Get into real hills, throw on a small one, get into the flats put the big "cruise" roller.

The rubber ones have been great. Very little wear with 500+ miles. The oak drives as well and looks like it might last almost indefinately. Have just started with them so remains to be seen. Got caught in a summer shower and the rubber continued to drive, but there was some slippage at high throttle. No experience with the oak in this respect yet.

That is a point to ponder, how to shift it with out getting extreme on the engineering. Maybe a slotted engine mount with a heavy spring to hold it in "hi". A shift lever to pull it down to "low". Probably mounted to the top tube with a gate. Once you get rolling good shift to hi and the spring pulls the engine/hi roller over to engage the tire. You would still need the lift clutch to do so. UNLESS the roller is a cone, which is a vari drive and would shift with out having to lift it. A shifter with a good friction lock would offer infinate positions.

As to the crank bearings, I doubt they are any more loaded than with a belt in tension.