Yet another way to dispose of income

[microbore]

Note: if this post is more than 10 minutes old, the bike probably has been modified.

This is my first motorized bike build; a steel framed Schwinn Delmar. By the time it was completed I had replaced everything on the bike, keeping only the frame, fork, and seat.

My first priority was to upgrade the brakes. I installed the front disc brake on a mount I fabricated from a piece of 3/16” x 3” steel bar. I created a jig to locate the mount properly and to hold it in place while I welded it to the fork. The front wheel was built with a Shimano XT disc hub and the brake is a mechanical caliper Avid. The rear brake is a BMX side-pull style with a 94mm reach bolted to the underside of the fender mount.

The next objective was to fit a multi speed freewheel into the frames narrow rear dropouts. I cut a rear hub from existing wheel and replaced the 6 speed freewheel with a 5 speed to narrow the hub to 120mm. I laced the hub to a Sun rim and dished it to provide the proper chainline on the engine side. To improve the gearing range, I replaced the one piece crank with an American-to-European bottom bracket adapter and a Sugino crank with a 48 tooth chainring. Now I can pedal-assist the bike up hills at close to 30 mph.

The engine is a Grubee Star-fire and is unmodified with the exception of port-matching the case to the cylinder at the transfers. The engine is mounted to the downtube with a mount made from a steel PVC pipe clamp. I made the exhaust from a Tomos moped muffler after the original fell apart on my first ride.

Miscellaneous mods: Threaded to threadless stem converter, Bontrager bar and stem, pit bike throttle, Shimano rapid fire shifer as clutch lever, Shimano bar-end front shifter converted to thumb operated rear shifter, and fabricated sprung chain tensioner.

My foundation is complete. Future plans include an expansion chamber, Dellorto SHA carb, smaller rear sprocket, and porting the cylinder.

[freewheeling frank]

i like yer chain tensioner idea, but quit yer *****en, work harder -longer and keep smilin, good day, frank

[microbore]

Just to clarify that title - read it as "I have found another enjoyable pastime to compete with finite resources". I'm not complaining. As for the parts I've replaced; I had most of them already and found them better suited to the intended purpose.

[azbill]

I would like more details on your coaster to cassette conversion
I am thinking of converting a stretch cruiser frame to use a derailleur (for pedalling with the girls, I need gears! )
but, I cannot find much info thru google

[Kevlarr]

That has got to be the best chain tensioner idea I've ever seen!

Look at it this way, it could be worse you could own a boat.

[freewheeling frank]

just joshen ya amigo, ya boats kinda like jeeps

[microbore]

Originally Posted by azbill

I would like more details on your coaster to cassette conversion
I am thinking of converting a stretch cruiser frame to use a derailleur (for pedalling with the girls, I need gears! )
but, I cannot find much info thru google

The hub I used was from a little used 6 speed kids bike. It measured around 130mm wide, but with new spacers (10mm washers) and a 5 speed freewheel, I was able to reduce the width to a point where I could spread the frame enough for it to fit. Another possibility is to use a BMX hub (110mm wide) and use a 5 speed freewheel but the BMX hub would likely require a longer axle. As for the derailleur, I used this:


I filled the slot and redrilled it so that it is fixed to the axle. I welded the 6x50mm bolt to it so the derailleur also serves as a chain adjuster. This bolt fits into a slotted tab I welded on the back of the dropout.

Originally Posted by Kevlarr

That has got to be the best chain tensioner idea I've ever seen!

Thanks. I probably should take some additional pictures of it and create a separate post.

I know what you're all thinking: "Why use a tensioner at all if the axle is held with adjusters and a derailleur is being used"? The chain would still whip around a bit from any eccentricity in the sprocket. The spring-loaded tensioner seems to smooth things out a little. With a better sprocket mounting, I could lose the tensioner.

[Kevlarr]

Actually I may just steal your idler design for my BT build even though I'm going to have axle adjusters and I have an adjustable motor mount idea floating around in my head.

[rockvoice]

hands down, the best tensioner iv'e seen.