Cool, thanks... I'll be picking up one of those then! I've found a couple of Makita 12v drills with missing batteries knocking about that I'll rip apart, lock up the transmissions and use for drive motors... get some motor mounts CNC'd including a HDPE surround for the gearbox to give it a bit more structural strength if (when) it gets smacked by something.

Any suggestions on speed controllers? I foresee many blown up mosfets if I end up working out my own, so I imagine I'll be buying them - I've heard the best are from robo-challenge with regards to not blowing up, but their store seems to be down at the moment?

Awesome posts guys, this seems to be going well so far... as for the CO2 thing, I'm happy working with regulated CO2, but full bottle pressure has me a bit concerned at the moment... at least until one of you guys fills me in on how to do it right.

As for weaponry, the problem I've foreseen with a big axe is that such a light machine would just go flying off the ground from the recoil of a powerful pneumatic axe, which is what's put me off the idea a bit... that, and the fact that everyone and their mother seems to be amoured up with Ti, 10mm HDPE, Hardox etcetera. from what I've read on here, and the kind of power needed in an axe to put a dent in that would definitely send me bouncing all over the place... ahh, what the hell, it'll be fun trying

If anyone knows how the hell Terrorhurtz seals their ram, I'd like to know... from what I know of their mechanism the rack teeth cnc'd into the ram would chew up the seals horribly. I suppose on the return stroke you don't need too much efficiency or force though, so an imperfect seal wouldn't be all that much of a disaster...

Once again, thanks guys!

[Edit] I'm pretty much leaning towards a rack and pinion axe, or Final Destiny-esque skirted bar spinner for the design... now to go ahead and work on details.