Moving the Pedal Chain

[Timbone]

I am now working on my OCC Chopper motorized bike project. I've mounted a motorcycle tire on the back which causes problems. I am going to jackshaft the motor chain left to clear. The right side pedal chain is just grazing the tire.

Anyone know some simple cheats to move to pedal chain 1/4" or so outboard for tire clearance?

 

[Frankenstein]

Bolt a sprocket to the outside of the original sprocket with 5 bolts a quarter inch away from the original, use a bigger sprocket to clear the original, and use a 3 speed chain.

 

[Timbone]

Bolt a sprocket to the outside of the original sprocket with 5 bolts a quarter inch away from the original, use a bigger sprocket to clear the original, and use a 3 speed chain.

That's a very clever idea. The only problem I have the only cogs I have are 9 speed Ultegra racing cogs, mounted in small blocks (e. g. 19-21-23). If I can find an adaptable lonely sprocket cog, 21 or so, I will try this.

 

[Frankenstein]

Scrap yard tends to be LOADED with spare bicycle parts. And the curb on recycling night. Chop shop.

 

[Timbone]

Frank, you inspired me to chop a 25T cog off of a racing cassette and it will fit perfectly, allowing me to move the pedal chain 3/8" to the right. I think I will also fashion an outer ring to serve as a chain guide to keep the chain from falling off.

This should work. Thank you for the idea. I'll take pics and tell you if it works.

 

[Frankenstein]

Chain tensioner along the lower side of the chain near the rear sprocket, a multispeed chain will handle the feeding on the front sprocket if it's not too far off, think how a 21 speed bike works, the chain can be on the inner chainring sprocket while the other end can all the way up on 5 (or even 7 but not normally recommended) and the chain does fine without having a guide keeping it in place on the front, usually the front shifts with a friction type shifter the pushes the chain off to the next cog, but doesn't normally retain tension or pressure on it to keep it there.

Most problems with chains falling off happen as the gear rating lowers on the chain, the less gears it can handle usually the more stiff it becomes to bending left or right rather than just around a sprocket. The stiffer it is the less it can handle being misaligned, and of course the more gears it can cover then the more flexible it would need to be. Chains meant to cover 8 or 9 speed cassettes normally get off alignment by more than an inch anyway so less than half an inch shouldn't be outrageous, maybe give a 5 speed a go and it will hopefully be wide enough to fit on both sprockets.

I bet it looks pretty cool, stuff like gears bolted to other gears just looks cool and can be made really decorative.

 

[Timbone]

 

[Timbone]

Here is my new offset 25T rear sprocket. A bit tedious, using 10 points of connection, but solid as a rock. I'm moving the pedal chain a full inch to the right and it clears nicely. Just had to add a 3/8" spacer on the axle.

Thank you, Frankie, for the idea!

 

[Frankenstein]

No problem and that looks almost frightening even to me. Put blue locktight on the threads and then try to use a torque wrench to evenly tighten all the bolts, reduces chances of it getting loose.

 

[Timbone]

I commented in another thread. Yes, blue locktite. Thanks!

After fitting the thing up, I had to cut off the excess length of the 6mm bolts for clearance. Added a spacer to the axle and my chain test fit was fine. I'll present final pics when it's complete.