Is it possible to create a sort-of a skewer ballista?

     I just caught wind of another idea while commenting on some instructable on a skewer gun. It got me thinking for a moment when I said "Is it possible to make the range around 80 feet or so?". Then, poof! My idea just came through. So, is it possible to create a sort-of a skewer ballista? Something I can fold up into a compact size for storage. Sort of a challenge already huh?

Something like this?

Couple of mods for storage, and you're there.
 nope, not that. That is a crossbow. What I'm talking about is a miniturized ballista. A ballista is basically an oversize crossbow. So i'm talking about a ballista the size of a large, but not oversize, crossbow. 
OK, so this isn't helpful because it's a crossbow, not a ballista, (which is for all practical purposes a very large crossbow), and what you're looking for is a ballista, but smaller -  about the size of a largish crossbow? And so a crossbow (aka a smaller version of a ballista) is totally not it.