I'm trying to upload a couple of photos... being new mean 'learn this editor' ( Seems really Nice! )
hmmm... I think it worked !
The main point I wanted to do with this was to keep it simple but functional... aka Parts on hand, no welding.
The engine is a lil old and abused homelite 25cc weedeater.. its a bit underpowered for my location as I'm live near Seattle and there are steep hills just about anywhere you go. I learned alot about 'Roller size' and such from this! lol
The homelite as it turns out is VERY popular engine and can be dug up just about anywhere.. Very popular for Airplane RC stuff. its a rugged lil motor even though I broke the first one a couple of different times LOL.
The roller is 25mm ( real close to an inch diameter, cruises at 15-18 nicely,
can run up to 24+ mph. a 35mm diameter gets past 30mph with a lil peddling but is of lil help on the overpasses.
The motor is set in a 'Spring away/ dis-engaged' mode by default. The 'shifter' engages / disengages the whole assembly away from the tire. The spring is just enough to lift the engine.
The roller is a 5/16 bolt roughened up then built up using walmart 5 min epoxy and ( due to lack of sand I used cat litter, fortunately, it wasn't USED cat litter
The shifter is locked into place via the hose clamps on the crossbar ( I used a LOT of hose clamps), the motor's pressure on the tire can be adjusted using the hose clamps, and /or fine tuned from the 5 inch long screw and wingnut.
Too much pressure and it wastes some of what lil horse power this engine provides, too little pressure and the roller acts more like a grinder and can chew up the rear tire in no time. The fine tuning is for adjusting for the 'in-between'
The friction drive works great for its simplicity, but doesn't do steep hills well, however.. some of that is my weights at 230, but it does have enough power to help with freeway over passes. I think a 32 cc may make all the differance in the world, but I'll have to wait on that when I find an available engine.
The shifter... or How to clamp just about anything to your bike frame without drilling... Plumbers tape doubled over and hose clamps
Bailing wire from the 'board mount' to the other side of the BIG bolt... has a screw and lock washer setup for adjusting the support as the motor will want to go off to the side when engaged.
The kill switch.. a light switch I had, mounted with pipe cleaners
Lots of electrical tape.. why ?? to save the paint and I'm out of duct tape!
The engine mount boared is from a old skate board.. I didn't have any plywood around but should work just fine.
Throttle.. this was the hardest part! I gotta get myself buy a regular twist type, but im such a cheap bugger!! LOL The original ( not pictured ) was made from a peice of pressboard and worked ok. An L shaped piece of pressboard is used for part of the throttle linkage ( not shown, covered by gas tank)
Does it work ?? I have over 245 miles on the odometer and I have at least 100 on it before I added that. Yes, a lot of that was from Peddling back home and every turn of the carnk was well worth the great time I have riding it.
I turn the motor off and hit the bike trail, or turn the motor on and deal with the cars and/or overpasses.
I think I included anything that could be helpful. This is a very workable and cheap setup and the engines are aplenty. If someone waighs in closer to 150 they should be able to do a nice 35 on the flats with a 35 to 50 mm diameter roller! Nice thing about the homemade rollers besides cheap.. start big, then can always make them smaller by just taking a file to it while the engine idles.
Hope some of that is a help. Its more fun than any minibike and its street legal!