I got tired of waiting for other people to design a 3d-printable Big Gun cannon so I made one myself. This cannon uses BigGunJeff's 3d-printed Torpedo Cannon as a base. Download parts and instructions for them here:
The magazine consists of four layers.
Bearing layer, top right. uses one 3016-2RS bearing, 1/2in ID x 1_1/8in OD x 5/16in thick (6384K49). The coupling is a K&S brass tube 8139, 1/2in OD from Amazon. Two #4-40 x 1/2in setscrews (92311A110) to adjust feed, up to four #4-40 setscrews to hold the bearing in place, and four #6-32 tapped holes for assembling the other layers.
Manifold layer, bottom right. curved to help redirect air towards the breech. Barrel spacing 0.6in
Breech layer, top left. ramps neatly fit 7/32 rounds, but can easily be drilled out to 1/4. There is a 1/4in wide x 1/8in deep lip, to allow installation of larger magazines on the same size base.
Magazine ring layer, bottom left. Single layer ring for 7/32 or 1/4, 3.5in OD. I will update with other diameters as I produce updates.
Riser piece, center. This piece is for holding pieces of K&S brass, brake line, or other material for the risers. Or you can install the barrels directly into this piece, if you don't want barrel depression.
lid: not designed yet. I can't 3d-print transparent materials, so this will have to be laser-cut or manufactured by hand.
Magazine height 1.5in
Magazine outside diameter 3.5in
cannon base height 1.25in
cannon base length 8in
overall height, 2.75in
accumulator volume 4cu.in.
Big Gun cannon magazines 1.0
Magazines for Big Gun cannons, Indiana style, compatible with other 3d-printed cannon parts