Desktop Mortar (January 19th, 2009)

Classes were canceled today, so I decided I'd try and make a Civil War style mortar that would shoot BB's. I've had this idea in the back of my mind for a while, but hadn't done anything about it. I built this mortar in just over two hours using scrap material from other projects. The wooden base is cherry and came from scraps from my steam engine base which was left over from a board I used to fix a cabinet door. The brass barrel was some 1/2" round bar that was used in a lathe project last semester at school. The brass rod that allows the barrel to pivot came from an earlier attempt at a steam engine that it still uncompleted.

Desktop Mortar

Here are the dimensions of how everything ended up:
Base: 1" wide x 1.75" long x 0.75" tall
Barrel: 1.25" long x 1/2" diameter
Bore: 5/8" deep x 3/16" diameter
Pivot: 1" long x 1/4" diameter
Touch Hole: 1/16" diameter
Powder: 3.5 grains of FFF black powder

Desktop Mortar Firing

BB's are 0.177 inches in diameter and I used a 3/16" bit to drill the bore. It's a little too big, but I don't really need the mortar to be 100% efficient. When I shot it, I heard the BB land in the woods so it went at least 35 feet. I tried a number of times to get it to shoot through a tin can, but I can only get 3.5 grains of black powder into the barrel. That limits compression because the BB is so close to the end of the barrel.

This was a fun little project that doesn't really require a lot of specialized equipment. I only used a drill press, table saw, and assorted hand tools.