Rim Drive

ferball

ferball

New Member
My next project is gonna be a weed whacker friction drive. Has anyone experimented with friction drive on the rim instead of the tire?
 
If I came across a light weight vertical shaft engine I might try to work it out like a brake on the rim
 
deacon said:
If I came across a light weight vertical shaft engine I might try to work it out like a brake on the rim
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That was one of my crazy thoughts that I nixed as to ambitious/complicated. Use the flex shaft from a weed wacker to power some sort of roller head on a caliper brake type set up, if you put an idler roller on the other side it could squueze the rim quite nicely and if you are just moving the roller it could easily be engaged/disengaged with a brake lever type system.
 
I was thinking more like a scissors action with the complete motor moving horizontally. It would only have to move a quarter inch. Drive would be something like a skateboard wheel
 
I saw a youtube vid of a bike with a vert. lawnmower engine driving the sidewall. It had an opposing roller. They had used a big engine like 6hp. Fit well. Was a power house. Unless you live in the flats a weedeater is not going to have the desired power.
 
On hills with a weed eater you need a five or six speed rear end for sure. If you don't want to pedal at all, those 2.5 hp are minimum. I think for friction drive,.they will cimb hills that choked down the chain kit bikes. At least that was my experience with them.

I actually didn't mind the 35cc or so bumble bee bike with the five speed rear end. I could get the gearing pretty good so that I could help it when it first started up the hills. Then when it got to the really steep parts I could down shift and still have the bee helping me along.

But i do prefer not to pedal at all lol.
 
I am not planning on my weed eater bike to be high speed, I want to use as an actual peddle assist, instead of like a moped. I am gonna put it on my MT bike, but my understanding is that the knobby tires are not the best match with a friction drive, hence the rim drive idea. I have my HT with nice stretch frame and a jack shaft for cruising and minimizing peddles, but I miss mountain biking, and being old and fat a little help peddling would make it more enjoyable.
 
To be honest I run whatever tires I have available on my friction drive. I think most of the problem from knobby tires is more the vibration than the friction issues. The big ole 2.5 hp has a really heavy duty drive shaft, which seems to be able to stand up to the punishment.

My experience with weed eaters is that they require more finesse than I possess. If I hang them over the side resting solely by the drive shaft on top of the tire they seem to fall apart on me. Now I do believe that if you were to find a way to support your roller on the end with a bearing it might solve that problem.

I had given some thought to a chain/friction combination. In other words a sprocket attached to the end of the drive shaft of a weed whacker probably one without a clutch.

then mounted under the motor would be a spindle or roller mounted with a bearing on each end and a sprocket available to hook the chain to. It would be the same as the wheel on a wheel but much smaller. that would probably solve your vibration problems. yes I am a wheel on wheel advocate even though I am not using one at the moment.
 
Im telling ya the side wall drive was awsome. It allowed the use of a cheap lawnmower engine(20 bucks at the average lawn sale) The common B&S 3.5hp is small and pretty light, and every where you look, tough too. With my method of making drive rollers the 7/8 shaft is not an issue either. This setup could clutch with a hand lever just like the horizontial engines.
 
That was something else I wanted to look at was a side wall drive, but how well does the sidewall grip and wear as opposed to the thread?
 
The side wall should maybe in theory should grip better, at least in the dry as it would offer more contact area as it is smoother. I dont think wear would be a real issue especially if using a rubber drive roller. The opposite side wall had an idler made from a skate wheel backing the bike wheel up, the engine was spring loaded into the wheel with a lever clutch. Very simple. The only added construction over a normal type friction drive was the opposite idler.
 
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