It has been taking forever to get a coupler made up since I got the engine out and got at the clutch disk.
I also want to note that I didn't fully document the design and construction of this because it is based on someone else's design. I was inspired by the electric-lemon who showed it is possible to do this with a simple sprocket and some spacers (he had a fancy machinist lathe though, whereas I got by without)
The total cost of materials for this was about $100CAN. (can be cheaper in the future)
Omitting some failed experiments, I've finally devised a way to put this thing together without using a machinist lathe.
It all came down to discovering the exact measurements of the mounting bolts.. in each set of 3 holes the outer 2 holes are EXACTLY 1 inch apart. Also, the diameter is EXACTLY 5-1/4 inches. I tried to measure these initially, but had difficulty due to the awkward shape of the clutch disc, (and not owning calipers)
I tested this with cardboard before going to metal. I used a compass to draw a circle of exactly 5-1/4" D
This was done using only a ruler and a square tool (it had a 45 degree part on it too)
initially I thought making a guide pin (using my drill press as a lathe) would help center the clutch disk. This turned out to be unreliable as I learned that the center of the disk (splined part) is actually being suspended by the springs and can move around (off center)
Here are some pictures of the finished product mounted on the electric motor. And below, the coupler attached to the transmission. (I cut the guide pin of the drive shaft after ruling that it will save me a lot of work and money with adapter plate spacing, and also that it will never be needed. I smoothed the cut of the pin by putting the truck in 4th gear with one rear wheel raised and I got a friend to spin the tire; thus spinning the drive shaft allowing for a nice even cut.
(updated Oct, 21, 2008.)
Update: Feb 6, 2009
There has always been a debate weather to incorporate the clutch or not. I was thinking clutchless for a long time, but this document, (specifically page 42) settled the argument for me once and for all.