Originally Posted by ianjk
1. You have a couple options:
c) Mate fork from top bike to stem of bottom bike. I've seen pictures, but never seen one in action.
this works well, if you have decent parts. also, this method requires no welding.
here's what you need(aside from normal parts. this is the list of stuff you need to connect the bikes):
one bottom stem, preferably steel, or a bmx or threadless kind, with a removable face...
one top fork.
one front hub, wheel and spokes removed, axle, nuts, etc, intact.
pry open or unbolt the front of the stem. insert the hub in there, and tighten the stem around it, like it's the handlebars on the bottom bike.
put the top fork thru the top headset, adjust tension like normal.
now, pretend the hub is your front wheel, and mount it on the top fork. tighten the axle nuts.
this will most likely put the seat pretty far back owing to fork/headset rake, but you can flip the stem, and/or the fork to help push the top frame forward, to keep from making it too back-heavy.
let me know if this isn't clear, and ican take some pics of my current setup that uses this doublestack technology...
also, you might wanna check out the photo gallery forum on zoobomb.org, that's where i got the idea.