My first attempt at building a crossbow worked out pretty well ( I had pics up but I guess the file was too big), and I'm inspired to make a more refined model.

Just got an excellent book from the library, written in 1906.  It's a detailed history of the weapon, including instructions for building several different types.   ( The Crossbow, Medieval and Modern, Military and Sporting, It's Construction and Management.....Hehe- those turn-of-the-century authors....)

Anyway, there are limits to what you can do with a wooden bow.  I intend something in the 150-175 pound range, and wood tends to be excessively thick and heavy.
I can, of course, just buy a steel prod from Alchem for about 60 bucks.  Still, I'd rather make....
For years, I've heard that an automotive leaf spring can be used.  In fact there are dozens of references on the Web to this effect.   BB posts, little factiods, that sort of thing.  "All you have to do is get an automotive leaf spring!"

Unfortunately, I can't find a single reference as to anyone who's actually done this.  No pics, no build-a-longs, no articles.    
No dimensons, no information as to what size spring to look for, etc, etc.

If you look at auto-parts sites, it's obvious that there's a very wide variety of springs available, from very light (like for trailers) to very heavy (trucks).
All these have a pretty strong curvature built in, which would seem to either limit available power or cause excessive draw length.
And it appears you'd have to do a lot of cutting and grinding to remove the shackle mounts and cut notches for the string. 

Anyone know of any references at all?

I actually thought of that; if the spring were not too severely bent, you could string it "backwards", making a deflex design.

There might be problems with failure, but it might be something to experiment with.  I may run by a local salvage yard this weekend just to see what's available.

Hehe-I belong to a dozen Yahoo groups, wonder why I didn't think there would be a crossbow-oriented one.....

hey bikewer, i saw something about leaf spring crossbows, posted by user "hellfire," if not on this forum then on another.  his had a draw weight of something like 1000 lbs (he cocked it with a hydraulic press), and fired a chunk of re-bar, if I remember correctly...  (he cautioned people not to repeat it due to the extreme danger).   I'm sure that you're aiming for something a little lighter and more practical.  Don't know if he stacked the springs or not.  if you want i'll look for it, but tonight i'm a little busy.