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Friction drive wheel material

a-dam

Member
Joined
Feb 18, 2008
Messages
30
Hello.

I've tried many searches and read many posts, but can't seem to isolate the info on drive wheel materials. A few have mentioned using steel pipe with either welding spatter or abrasives epoxied on for "gription".
Well, first, here is my situation. Building my first motoredbike; a 1970's Schwinn Continental 27" ten-speed with a 25cc Homelite blower engine. The motor will be mounted on the seat stays just above the rear brake bracket.
I live out in the country, six miles from the nearest town. Most of my riding is done on well-paved country roads, which is the way I like it, but I would like some assist for the windy days and to extend my range a bit. Most of my rides take me between 10 and 25 miles from home, so I've seen just about everything in that 25-mile radius. I plan to still pedal with the motor going for a speed boost. On leg power I average about 15 mph. I think 25 mph would be great, and I hope to keep the motor around 5000 rpm or lower to keep down the noise and wear & tear. The bike won't be used off-road, and almost always on dry roads. I ride like an old lady going to church on Sunday (unless a farm dog is chasing me).

Right now, I have a skateboard wheel setup from a seven-dollar KMart skateboard. Urethane, I think. I want to find a material that is hard enough to last a while but soft enough to minimize wear on my bike tire. The skate wheel seems pretty firm; it doesn't "give" when squeezed hard with your thumb. But it seemed to wear a bit during my test run. I had the bike on a work stand in the basement (too cold in the garage!) bump-starting the motor (the only way it will start) and adjusting the carb. I didn't have the tension spring connected during my fiddling - just used hand pressure. I think there was too much slippage, and the drive wheel got a groove in the center from the ridge in the tire. That got me concerned. I'd rather replace friction wheels than tires, but not every two days. It might end up working OK after all if I keep the proper pressure on it. I've never had it out of the basement, so I can't know what it will really do until it gets on the road (come on, springtime!).

So, finally, here's my questions. What do YOU use for homemade drive wheels? Has anyone had success with rubber wheels? How long do your friction wheels last? What kind of tire wear do you experience? Will a knurled metal or stone wheel be gentle on a tire if slippage is avoided? Got any idea how hard the friction wheel is pressing on the tire? I don't have a fish scale, so I'm not sure about my setup. I guess about 15 lbs total with the motor and tension spring. My skate wheels are 1.5 in wide and 2 in diameter when new. It will have about 1.5 in diameter once its shaped to the tire. That should give me about 20 mph at 4000 rpm. That's what I'm shooting for. I can fabricate what I need once I know what material/surface will work best for me.

So please share your knowledge with a brotha'. I'll post pics once I get settled in here.

Talk to me,
Adam
 


K

kerf

Guest
If you have slippage you have wear, tire or roller but somethings gonna "grind down". For that reason I like knurled steel, not over 1 3/8" diameter, 1 1/4" is better. As to tension, there is a trade off, too much cost power, too little cost tires. Roller diameter, tire pressure and profile all have an effect but the needed tension will require a high speed ball bearing on each side of the roller.
I would look around at some of the friction drive manufactures for ideas as to design. Try Staton, he makes a very good unit but there are others as well.
 

Esteban

Active Member
Joined
Dec 1, 2006
Messages
1,029
I have a vintage Ohlsson & Rice engine on mine, & it has the original steel drive. http://www.motoredbikes.com/attachment.php?attachmentid=2906&d=1195142914
It does very well & does not wear the tire, excessively, as long as you take it easy so it is not spinning/slipping. A tire will last a long time for me & I always have plenty bike tires around here. My motor, being on the front wheel, makes tire changing easier, too. It does better on smoother, wider city type tires than anything else. My owners manual says to mount the motor where the drive wheel compresses the tire about 1/8 of an inch.The roads around here are too rough to mount this motor on skinny bike tires. 1 1/2 " tires work well. Yes, it will slip in the rain. I have seen homemade rigs using pipe. A light mixture of crushed grit from a small grinding wheel, mixed into a paste of J.B. Weld, & coated on the drive roller will give better traction, but may be harder on the tire. I have also seen the drive wheel made from one of those BMX type bike pegs. They are already serrated a little & seem to do pretty well. It seems that we all have to experiment with different things & ideas to best suit our needs.
 

loquin

Active Member
Joined
Jan 11, 2008
Messages
2,214
given time, every thing wears down.

Check out the pics in post #4 here. These are hardened steel rollers!
 
I

ibdennyak

Guest
On my latest contraption, I used a Tecumseh snow thrower and a caster from a drum dolly. The caster was about 3 1/2 inches in diameter with a 5/8 bore. The engine shaft also had a 5/8 diamter, so I just slipped it on the shaft, and cranked the retainer bolt down hard. Then I started the engine, and ground the caster down to about 2 1/2 inches. It works fairly well, but does like to slip in rain and snow. I use a happy time clutch cable to pull the caster against the tire, and a bungy strap to release it. The engine is rated at 4400 rpm, so it is plenty fast. The caster could be taken down a little more. Wiped out on an ice patch yesterday at maybe 25 to 30 and it wasn't straining. The tire doesn't seem to wear appreciably, and the caster is like $3.00 and half an hour to replace. Unfortunately I blew out the rear tire when I went down, so I had to drag a broken bike about 4 miles home while dripping rain and snow. Ego was bruised more than the old carcass, althogh I wouldn't recommend it as an Olympic event. Hard to convince anybody I did it on purpose.

My next scheme is to use a jackshaft scrubber set up with a pneumatic dolly tire. Thinking it might slip less. Smallest I found so far is about 6 inches, so it will have to be geared down. We'll see. :D
 

loquin

Active Member
Joined
Jan 11, 2008
Messages
2,214
If you used the back end of a gas scooter with a CVT, including the tire & face it backwards? Get an "off road" tire on the scooter rear end & it should get good traction without excessive wear.
 
F

fetor56

Guest
This is what a friend used.It was made in a machine shop,it's ribbed high tensile steel in a concave shape.
Since it's concave it hugs the wheel more and is better in the wet....tyres also last longer.
drive.JPG
 
Joined
Jan 25, 2008
Messages
180
I'm using a skateboard wheel assembly, and it seems to work pretty well.
I do notice some wear, and I think I might get less wear with a steel roller.
I also feel the skateboard wheel material grinds at the tire a little too much
even with adjusting pressure, but I'll know more after a few more rides.

It does work though...
 
K

kerf

Guest
I always carry a tape measure, if I do a face plant the idea is to jump up and measure the skid marks. I tell anyone watching, I'm doing a government study on bicycle crashes. I have to leave quickly before they start thinking of crash dummy jokes.
 
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