Freewheeling crank axle help

[Nanoha]

Hi guys, I've got Matt's 2 stage drive and a lifetech 36V15AH lifepo4 battery on order.

I'm having trouble finding an appropriate axle for a freewheeling crank setup.
Apparently will need a longer axle to accommodate the freewheel, but how long?
I'm considering ordering my parts from http://www.sickbikeparts.com but they have around 6 different
axles.

I still haven't thought about the different sprockets I'll need yet LOL

All this will go on to a Trek 3900. I have attached a photo to help clarify the situation.

Please help!

 

[amberwolf]

Sounds like you basically want a Cyclone freewheeling crank setup, like what was just sold last night in the ES marketplace. The kit on SBP is similar, perhaps even uses the same parts (I don't know). Length of axle needed will be determined by how things line up on your bike, so that the chainline from the motor/reduction output will be straight to the driven sprocket on the cranks. You might want to check with SBP to see if they can tell you which one to use based on the measurements of your bike and motor output position.

 

[Nanoha]

Thanks for the reply, originally I thought that all the cranks had some sort of universal spacing akin to the disk brake mounts on
a bike.

Regarding measurements, it's impossible without the 2 stage drive in my hands.
I thought it would be ideal to order all the parts and time it so that they all arrive roughly
at the same time to lessen the painful wait

 

[amberwolf]

Well, it is possible to do it if you simply decide you're going to force everything to line up a certain way, and build mounts for the 2-stage that cause that to happen. Or if it has an adjustable position for it's output sprocket, then use that to line things up.

There is a sort of universal spacing for standard chainrings, in that there are standard spacings you commonly see, but they don't really have much to do with how *this* setup will be, as you are essentially just adding another chainring on there for the motor to run, IIUC.