Jack Shaft Shift Kit

ferball

ferball

New Member
I am still waiting for the engine I ordered to get here for my first build, so my research continues and has brought me to shift kits. From what I understand the shift kit of choice on the market is the SPB one. From my understanding it is pricey but worth it, my understanding is though that you have to rebuild your crank so it has a free wheel hub, hence the alot of the price.

Is there a kit that does not require a hub rebuild, instead it is like a bolt on jack shaft with a third sprocket that freewheels and goes to my pedal crank? Is this design feasible? Has it been done? I don't feel like reinventing the wheel, or my pedal crank for that matter. I am just wondering and I may be way ahead of myself, but I have to kill time until my motor gets here and I can get dirty.
 
The only thing that needs to be changed is the bottom bracket spindle to the longer one that is included in the kit. Very simple to do. The freewheel attaches to the cranks and is a very simple assembly. I recommend reading the installation instructions which will give you more detail on what is required for installation.
 
Checked out your instructions, (very nicely done I might add) now my question is this, your shift kit goes from motor to jack shaft to crank to wheel, why not go motor to jack shaft to wheel, and let the pedal cranks hit the jack shaft on a free wheel sprocket. Am I making sense, or does the design not work? I haven't tried it and I am looking at putting the parts together to make one, but if it is already out there,l it would be easier to buy a kit. But if it has been tried and failed, why waste my time.
 
Your idea makes sense but not practical because of the chain line. If you run a chain from the jackshaft directly to the rear wheel a rear derailleur won't work because of the run of the chain from the jackshaft to the rear wheel. It can work with an internal hub or NuVinci that way because there is no derailleur and the hub doesn't care what angle the chain is coming from.
 
Would an intermediary sprocket/pulley (ala the idler pulley in standard engine kit) work to route the chain properly? but once you get into that, your set up starts make more sense, thanks for the input. I am anticipating lots of hours in the garage messing with my bike, and hopefully as much time on the trails and road.
 
Ferball.
Perhaps this is what you had envisioned. It only uses a standard freewheel as only crank power and not motor power goes thru it. These are old pictures, and now the bike has a lot of trouble free miles on it.
 

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yes it is exactly what I was thinking, is that a kit you can buy or is it something I have to cobble together myself?
 
Ferball,
It is a DIY setup but can't get much easier if you have hand tools and a welder.
It has worked out very well.
The jackshaft kit can be bought from most any go-cart supply.
Some on here used bearing blocks and that probably makes it even easier.
The SBP is a good reliable setup unless you enjoy DIY stuff.

Jim(Russell)usflg

PS: No idler required
 
Looks like a sweet drivetrain setup. Is that sprocket on the left side of the rear wheel just a leftover from a previous "normal" configuration?
 
A_dam,
Yes it was left over from when it was a 1-speed. It has been removed but do not have updated pic. The drive unit has been very dependable.


a_dam said:
Looks like a sweet drivetrain setup. Is that sprocket on the left side of the rear wheel just a leftover from a previous "normal" configuration?
Click to expand...
 
Ghost0 said:
The only thing that needs to be changed is the bottom bracket spindle to the longer one that is included in the kit. Very simple to do. The freewheel attaches to the cranks and is a very simple assembly. I recommend reading the installation instructions which will give you more detail on what is required for installation.
Click to expand...

is the installation instructions for jack shift on video or pdfxct2
 
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