New Friction Drive Build -featherlite 25cc

[motorbikemike45]

You will do better with a smooth "street" treaded tire, especially in the center of the tread where it is in contact with the roller. Nice build. The only trouble I've had with my friction drive bike is with the rear wheel. Since we travel at greater speeds than pedaling alone, I've broken some spokes, knocked the rear wheel out of true, and bent a rim hitting bumps. You may need a much heavier duty rear wheel over time.

 

[velosolex]

Nice looking build! I've been doing friction drive builds since 1972, and have found urethane (medium durometer) to be a great friction material for riding in dry weather. The urethane can be purchased in rod form, drilled out and pressed onto a steel or aluminium "mandrel" that can be knurled before pressing so the urethane will not slip. Over time, the urethane will wear slightly and offer better surface contact with your tire. Urethane will not work on wet streets! Carry an aggregate lined roller for wet weather and switch out as required. I've run rollers as small as 7/8 OD on small weed wacker engines, and as large as 1-1/4 OD on 49cc, 2 HP 2 strokes. If you run a big engine, find yourself a Solex friction roller on eBay or contact Velocruz up in SLC, Utah and they will sell you one. You'll have to fashion a mandrel for the roller, but they work better than anything else I've ever used. They have to pressed hard against the tire, but tire wear will be much better than what you are experiencing. Your current emery cloth roller will sand your tire to death in short order (ask me how I know)
Nice thing about your small engine is you can build yourself a quiet exhaust and go riding without anyone hearing you. I've used engines as small as 21cc's.

Cris

 

[tom80]

I have a go-ped motor 23cc on my friction drive mb. I have found the black magic roller to work very well in wet weather.

 

[velosolex]

If it works for you, thats great!! Let others know where you bought it from and maybe give details as to cost and your buying experience(s). Perhaps you can give us a detailed source for this drive component?

Cris

 

[tom80]

I bought this spindle from ddm and it is used for a go-ped. The spindle has 1 mm deep channels cut in it all the way around and is heat treated. Spindle size range from .625 - .950 and cost about $21.00. I used the .750 spindle when my motor was stock and could keep a steady 25 mph and light peddling to maintain 25 mph up hill. I also tried the .950 spindle and could hit 27 mph but acceleration was lost. I weigh almost 200 and it would still climb most hills and the sound level was way down. They also sell a ADA racing 54 mm clutch kit made to drive this type of spindle for around $75.00. My 23 cc motor made 2.0 hp stock and about 1.0 ft lbs. I bought all my parts from ddm and have got great service and the tech line will help to insure parts are compatible. ddm mainly sells go-ped, pocket bike and rc car parts.

 

[velosolex]

Tom,
How well is your tire holding up with the spindle(s) your using? I don't know how goped tires compare against bicycle tires regarding number of plys, thickness of rubber on tire and durometer of rubber compound. Note tire diameter of goped tire is much less when compared to 26" bike tire meaning that ratio of spindle to tire diameter is much different when comparing both applications.

Cris

 

[tom80]

I have the tire set at 90 psi and is a 1.5 slick. I did not even consider the number of plys or hardness of rubber. I will look into it. So far my tire is holding up great. Probably got lucky. Thanks for the info. I am not understanding the spindle to tire ratio. When I do the math using same .750 spindle top speed for both bike and scooter are the same. In real life the scooter will probably be faster due to tire hardness. Please let me know what you mean.

 

[velosolex]

Tom80,
I was wrong about the tire diameter coming into play with friction drive. Actually tire diameter will have no impact. The way it all works is just as if the friction roller were running along the ground. All the tire does is act as a go between the roller and the pavement . It's been a while since I've done the calculations but here's how I figure it:
There are 63,360 inches in one mile
Your roller diameter is .75" x 3.141 = 2.36" in circumference
Your roller must turn 26,847 times to go one mile
Say your engine is turning 5,000 rpm for one mile, it will take 5.4 minutes @ 5,000 rpm to go one mile. Last 60 mph / 5.4 minutes = 11.1 mph travel speed

Cris

 

[loquin]

simplified,

Speed = RPM * D / 336.14

where speed is in MPH and D is roller diameter is in inches.

 

[velosolex]

loquin,
Very good simplification


Cris