Desktop Sized Mountain Howitzer (July 10th, 2009)

I always planned to make a field style cannon after making my naval style desktop cannon. My desktop mortar was a sort of creativity stopgap, I still planned to make a field gun at some point. During a machine shop class last year I kept all the bits of brass I could find to use in future projects. The biggest piece was 1.75 inches of 1/2" round bar and that's what I used for this project. The proportions are off to make a normal cannon, so I found a design for a Mountain Howitzer. It's a lot stubbier and my piece of brass works out to about a 1:22 inch scale.

Finished barrel and test carriage

First I drilled the bore. I used a 7/32" bit and drilled 1-3/8" deep. Then I drilled the holes for the "trunnions" or the bars the barrel will pivot on. These are drilled slightly below the centerline so the gun will sit higher. Next I found the bottom of the barrel and drilled my vent with a 1/16" bit.

I have no metal lathe at home, so I had a huge problem shaping the outside of the barrel. Eventually I decided to chuck the piece in my drill press and use a bunch of files and sandpaper to shape it. It was very time consuming and boring, but eventually I got everything shaped out good enough. The bands around the barrel aren't as pronounced as I'd like, but filing was taking forever.

Next I made the trunnions. These are bits of 3/16" round bar that I put some 10-24 threads on one end. I also used a tap to put matching threads into the trunnion holes. After making sure they fit, I J-B Welded them into the sockets and drilled out the bore to cut them off flush with the inside wall. At this point the barrel was functional, and all I plan to do to it is some polishing to get rid of some file marks.

Barrel, two trunnions, and a dime for scale

I need to make a wooden carriage for it, which will be a lot more work. I haven't fully figured out all I need to do, but at last count I'll need to make around 50 separate items to complete the carriage. But just to give it a try, I made a carriage from a paperclip and two bottle caps to see how it'd work.

The firecracker will explode around 20' high after shooting the gun