Roller / pinion / spindle options other than BMX pegs?

[VTPete]

Hi All,
I do mopeds and motorized bike... but never a friction drive until this past weekend.
I took an old 25cc weed whacker, added a BMX bike peg to it and welded a quick support to hold it against the wheel. Rigged up a throttle and in two hours had a friction bike that works!

But it's got no power. On a slight downhill the bike accelerates nicely and around 20 mph the motor starts to sound like it's finally reaching mid RPMs. But, on the level you have to be going close to 15 mph for the engine to be efficient enough to move you well. I've played with the tension of the roller against the wheel, but in the end, I think the motor just isn't hitting a sweet spot with regards to engine RPMs.

The peg's outer diameter is 1.5 inches.

My gut is telling me that going smaller will help. Perhaps a 1 inch roller?

Has anyone got any experience with this... and if so, what are you all using for rollers?
I'm thinking I'll go to Home Depot, get some 1" pipe and weld a couple of washers on the end.

-Pete

 

[5-7HEAVEN]

You got the right idea.

A 1" roller OR smaller would do the trick.

See if you can provide bearing support on the outboard end.

That'll help prevent crankshaft damage.

 

[VTPete]

Thanks,
I just ran to Home Depot and bought a 3/4 inch pipe. It has basically a 1 inch diameter. Any smaller and I won't be able to get my socket driver down it to tighten the nut.
My problem now is attaching it. I picked up some washers that *almost* fit in it. My plan is to lightly sand them until they're snug in the pipe roughly 1/8th inch in... then weld them in place to give me something to bolt to.

Does anyone have any clever ideas for other spindle options?
-Pete

 

[butre]

more power is always the way to go

 

[VTPete]

more power is always the way to go

Ha! So true. But, in this case the challenge for me is "making do with what I have on hand." I have a 25cc engine so I'm going to rev her up and gear her down.
Last night I took three washers, welded them together, tapped them into a 1" diameter pipe, welded that and finished by inserting it into my drill press and spin/sanding it perfectly perpendicular.
The previous spindle diameter was 1.5 inches. So, I'll be going from a spindle with a 4.7 inch circumference down to 3.14159 circumference. That's basically a 33% reduction in horizontal speed which I hope fill increase my torque enough to propel me at least on the flat.

 

[Try18972-101]

I have a bumblebee bike motor 26cc China. It had an 1.25 inches neoprene roller that slipped even if it was humid. Got a 1.5 inch stone type and have the same problem as you. I'm desperate for a solution if you have figured it out. Tom

 

[curtisfox]

cannonball2 Made a bunch of different ones, one was a 3 speed hub for roller. Most of his rollers were made of oak wood.

Staton has just roller in different sizes, also

Here is one build https://motorbicycling.com/threads/...ck-mounted-scissor-lift-fd.63226/#post-659282

 

[5-7HEAVEN]

Ha! So true. But, in this case the challenge for me is "making do with what I have on hand." I have a 25cc engine so I'm going to rev her up and gear her down.
Last night I took three washers, welded them together, tapped them into a 1" diameter pipe, welded that and finished by inserting it into my drill press and spin/sanding it perfectly perpendicular.
The previous spindle diameter was 1.5 inches. So, I'll be going from a spindle with a 4.7 inch circumference down to 3.14159 circumference. That's basically a 33% reduction in horizontal speed which I hope fill increase my torque enough to propel me at least on the flat.

Actually more power is not always the way to go.

It depends what you want, reliability or top speed.
Sometimes, ya can't have both.

While I'm building my twin-engine,
I initially chose 2 "all-out racing engines".

Then I thought.....
two temperamental, unreliable engines.

So instead, I'll be using 1 "all-out racing engine"
and 1 slightly modified engine.

 

[5-7HEAVEN]

I have a bumblebee bike motor 26cc China. It had an 1.25 inches neoprene roller that slipped even if it was humid. Got a 1.5 inch stone type and have the same problem as you. I'm desperate for a solution if you have figured it out. Tom

Try a 1.25" or smaller stone-type, steel roller or deep socket.