2 speed direct drive shifting system?

[bikejock]

Been thinking about slapping together a simple 2 speed direct drive shifting system similar to how a traditional multi speed bike shifting system works. Basicaly it’s two sprockets bolted next to each other in two sizes; a 32 or 36 tooth on top of a 41 or 44 tooth sprocket & derailleur mechanism bolted up to it. I think it would be much simpler to install & manage RPMs better with than a jackshaft kit which I hear just wears out the bicycle drive faster.

Plus it looks likes these 415 chains can bend to allow for a derailleur style shifting setup. It would proabably need a custom heavy duty derailleur to handle the high RPMs of the engine & the 415 chain though. Ether way it sound much easier to deal with than having to tear apart your bottom bracket for a more complicated setup that just ends up eventualy wearing out your pedal drive faster. So what are your thoughts on this?

 

[bakaneko]

ahh. the holy grail. i thought about it myself. for what engine? 2stroke or 4? I personally would go with like a mid 50 and a 41-40

 

[bikejock]

ahh. the holy grail. i thought about it myself. for what engine? 2stroke or 4? I personally would go with like a mid 50 and a 41-40

It would be for a 2 stroke at least initially because the transmission design of the engine is simpler & more reliable than most 4 stroke transmissions. Also with a derailleur style direct drive shifter setup you wont have to mod your 2 stroke engine or bottom bracket just to get the thing to fit. Something that has always steered me away from buying a jackshaft kit.

With jackshaft kits at least what I’ve read about them you typically have to do mods to your engine like removing the studs for shorter bolts for the mounts & mill down the rear mounting block on the engine & usualy those kinds of mods are not possible for some builders like myslef that try to keep things simple or dont have the tools to do those mods.

 

[Steve Best]

2 hp or more doesn't like a loose chain, will not work well with a derailleur.
I've thought of doing a similar thing with s 2 belt system like this:

Tighten one belt, one gear, tighten the other, gear two...
Would probably still have to run it to a jackshaft.

Don't be afraid of the jackshaft.
You've looked at the prices and I can assure you they are worth the engineering.
The mods involved are just normal fitting and tinkering. Hacksaw and file will accomplish them all.
I know, I did it myself. So if I can do it, any idiot should be able to...

 

[curtisfox]

Steve is this yours? Don't see any belt guides , to help hold the belts round and to conform to the front pulleys. I like this setup especially with a small 2 hp size engine.............Curt

 

[Steve Best]

Steve is this yours? Don't see any belt guides , to help hold the belts round and to conform to the front pulleys. I like this setup especially with a small 2 hp size engine.............Curt

No, it is not mine, just an image off the web to show a 2 speed belt system.
Not the best illustration of good practices but it does show the idea.

 

[curtisfox]

LOL. Thanks, yep idea is what counts................Curt

 

[Timbone]

Been thinking about slapping together a simple 2 speed direct drive shifting system similar to how a traditional multi speed bike shifting system works. Basicaly it’s two sprockets bolted next to each other in two sizes; a 32 or 36 tooth on top of a 41 or 44 tooth sprocket & derailleur mechanism bolted up to it. I think it would be much simpler to install & manage RPMs better with than a jackshaft kit which I hear just wears out the bicycle drive faster.

Plus it looks likes these 415 chains can bend to allow for a derailleur style shifting setup. It would proabably need a custom heavy duty derailleur to handle the high RPMs of the engine & the 415 chain though. Ether way it sound much easier to deal with than having to tear apart your bottom bracket for a more complicated setup that just ends up eventualy wearing out your pedal drive faster. So what are your thoughts on this?

Good idea, wanting a 2 speed direct drive system (easy cruise @ 35mph), but it's a bad idea to think of a derailleur system with 415 chain.

They may look simple, but bicycle derailleurs, even on the cheapo models, are very sophisticated systems. It's going to be very difficult to come close to duplicating such a device in one fell swoop, especially with a roller chain that's not designed for the necessary lateral movement.

The answer would be a simple dog clutch. A box enclosing two different gear ratios and the dog makes the choice between the two. I've seen a design for this somewhere. Google Search!

 

[curtisfox]

Here is the belt one i like, like Steve showed has 2 different size pulleys on rear....................Curt

 

[bakaneko]

there is a "new" or relatively unknown 4-stroke design that another member posted that I wanted to try involving reversing the motor and using a SBP freewheel. if you are interested in that i can show you his posts and we can figure out the research and confirmation needed. i was gonna do it in the winter or spring but that is a maybe at this point...

and if it works put the detail build specs, material list, instructions, and perhaps an installation video for folks here.