I have been working on these for some time with a mate in Australia who is a very talented
CAD designer.
We've come up with a hybrid model of
MDF, card and plastic tubing that was intended to be a gun only that we could add to our ork trukks and battle wagons.
We made a base for it as well in case we wanted to use them for static artillery pieces.
I'm not sure about uploading video but the gun actually works... if you turn the wheel you can raise and lower the gun.
I'm very pleased with how they turned out - I must say.
I have added some more pictures to my blog here:
http://nothingunpainted.blogspot.com/