The Urban Buzzbike (sprocket reduction friction-drive with 2 1/4" drive roller)

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Build thread in the Friction Drive forum.

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rear view steel roller.jpg


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Just finished a 10-mile spin around the neighborhood. Rolling restart working good, pull-start after warmup takes one pull (for a weedeater motor, that ROCKS!!).

Stopped by store on the way home. Woman behind the counter tells me some older woman saw me go by the first time, shook her head, said 'I done seen it all now, someone put a weedeater on a bike...'.

Another bearded old man smiling, doing the twist-grip motion, I pulled in the clutch and revved it a few times and honked the horn as I went by the second time, made that smile bigger.

Seems older people see an old man on a motor bicycle, they smile.

I LIKE IT. Going back out.
 
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It's hard to understand exactly how it is getting good pressure on the friction drive but that's real cool. It doesn't look like it would be hard to add a derailleur and multisprocket to make it a multispeed friction drive... and you obviously have the skills.
 
The triangles create a toggle-lockup at the tire contact point. I had two springs, removed one.

Also shortened the clutch lever arm (moved cable anchor in) to increase the travel. More wheel clearance, and depreasion. Now I feel the accel, mighty micro g-force that it is.

Moved a spring inline with the clurch spring, acting as damper to the engine platform.

Two more adds, a chain idler topside, and chain guard (more to keep oil slinging away from me).

Wore the first chain out (from last fall), stretched. Gonna keep an extra in the bag too. That chain got hammered with 'experimentation'.

I don't think deraillers work at this rpm. Adding idler to dampen oscillation at low rpm now, its like a resonance, repeating. I can't see keeping enough slop to jump gears, at that speed its more controlling tension to stay on sprocket without running too tight. The idler lets me loosen the chain tension while controlling slop on idle side, engine tips into the chain tensioners under load. We'll see how these little sealed roller bearings hold up.

Considered two idlers, 'cause rolling restart shifts the tension side, but its not causing an issue, so I skipped that.

Also took dims to make a second platform for the 26cc engine, got spares, and wanna have one ready to swap when I blow the innards outta this screamer.
 
Post-Mortem Analysis:

I parked this project shortly after getting a trike and adding electrics. It’s biggest issue were chains. RPM way too high, it wore thru chains, smoked them.
My other consideration was adding a centrifugal clutch. It’d lose the bump-start, but make it easier riding rolling hills. These little 2-strokes don’t do well being pulled by load.

If I were to continue it, I’d swap the sprockets for pulleys.

Instead, now that I have a budget, it gets stripped off that bike, I have a 49cc to add to it.
May do a shift kit too, depends on how I like it w/o.
Building another longbike too. Got it on wheels, remote steer done, working on seat today. It will get something, not sure yet.

If anyone else goes that path, use SMALL sprockets, or go pulleys/belts....or a gear reduction before. Is it worth it to try it? Maybe...but I don’t know. How many FD drives out there cutting scoops out of their tires using small rollers?
 
I have built a bunch of FDs over the years. The beauty of the concept is to keep it simple. I have built several reduction versions that worked well but the added weight and complexity kind of defeats the simplicity of a direct drive. Using a larger four stroke worked the best for me. I had various size rollers that could be changed in under a minute, including a rain roller for wet weather emergencies. I still have and ride the bike 9yrs and 8k miles later. Its quiet, totally smooth, and a pleasure to ride. The bigger slow turning rollers are best.

If a reduction is planed, belts are best.
 
When I built it I was scrounging for anything I could make work. The plunge from middle-class to pauper was brutal. But I had lots of quality scrap to work with 🤣

I did wobble out the bearing in that first Ryobi, replaced it with the 25.4cc. That little engine still runs good with a larger intake and carb. I was already measuring and pricing for pullies and belt when my disability was approved with back pay.
I pounced on a used tadpole trike, added 750W mid-drive, and immediately put 300 miles on it in less than 2 months. I even invaded a PGA golf course during COVID lockdown, rode all 18 holes.

Stripping all this off buzzbike, putting a BBR 49cc smoker on it. Gonna reuse the pivot triangle, redo that 25.4cc as direct FD and put it on a Trek. Giving that away after it works, should be easy enough after building this contraption.
 
This was the last long ride on Buzzbike, it has the 25.4cc installed, and a flapper exhaust. That engine might make a good direct FD. Goal to make that one simple, light, on a light bike. This bike gets a remake, it'll be my main upright.
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