drivetrain jack shaft help

[Walker]

I've got a bike on paper right now that i want to have a two part drive train. left side drive at the crank then a second BB below the seat, transfer the drive to the right side and then down to the hub. I'm thinking that an english bb shell with two right hand cranks ground down to the spiders will work. Any other ideas out there for me?
Thanks

[JLarkin]

What if you used an old front hub? You could weld two rear cogs to large washers and mount them on either end of the axle. Then the hub would act as your bracket and would already have ball bearings in it. You might need to make a mount for the hub shell so it could be centered.

[Ed_Straker's_Rat]

I think Monstermetal did something similar on the RRBBO3 winner 'Madd Hammer':

viewtopic.php?f=25&t=9792

[UncleKudzu]

hey, Walker, is there any purpose or advantage to what you're doing? sounds interesting.

does anyone know if any efficiency is lost with a jackshaft?

[Walker]

hey, Walker, is there any purpose or advantage to what you're doing? sounds interesting.

does anyone know if any efficiency is lost with a jackshaft?

The only purpose is style, pure style

Not too concerned with loss of efficiency, i have no time to ride anyway

The hub idea is interresting. I coudl really cut down on the sprocket size by using some old gears off a cascette. It would have to be a steel hub so i could weld it into the frame but i think i could easily find one of those. got a couple of old 5 and 6 speed cascettes too. HMMMMMMM

[UncleKudzu]

The only purpose is style, pure style

well, i reckon that's reason enough it sure looked cool on that Madd Hammer bike.

i'm curious about jackshafts because some of the motorized bike folks are using them somehow to go through the gears of the bicycle to more or less shift gears under engine power.

It would have to be a steel hub so i could weld it into the frame but i think i could easily find one of those.

could you take the brake guts out of coaster hub and use that?

[NLCTVWguy]

You're on the right track. Any efficiency loss would be tiny. All tandems essentially use this setup- some have left hand drive for the first chain, most do not but the mechanical operation is the same.

A bb from any bike with a 3 pc crank will work fine. Im assuming you are up for cutting splicing welding type of work. Keep it all squared up and it should work just fine. A tensioner may be needed for that first chain.

Best of luck,
---Rob

[UncleKudzu]

Walker, check out this 3 speed jack shaft over at motorbicycling.com. he's using a 3-speed internal hub for his gearbox if i undertand it.

[Walker]

3 speed, i like it, and i have one!