BB Mortar build Advice wanted

[boiled_owl]

I must be the ultimate lurker here, member since 6-2009! First post.
I've combed thru this forum looking but haven't found what I want.
So far I have an oxygen bottle cut and a bowling ball, great start
What I'm trying to figure out is how to make the powder chamber, or is it necessary? I've seen where some have cut the valve end off and welded a chamber to the cylinder.

I would like to machine a trailer ball to screw into the valve threads to mount the cylinder to a base plate trying to keep this build simple. But I'm skeptical of the powder charge laying right under the ball.

All suggestions would be welcome.

My background: Gun kid, gun guy. Reloader since 1979. Trained as a tool and diemaker. Farmer for 28 years. Have lathe, welder, bridgeport. My son and I built a golfball mortar in 2009.

[Cat Whisperer]

boiled owl -

WELCOME to the board!   Good questions, DD often comes up with detailed replies on this one.

We're looking forward to seeing pictures of it!  (Including contstruction/design.)

[Double D]

So far I have an oxygen bottle cut and a bowling ball, great start
What I'm trying to figure out is how to make the powder chamber, or is it necessary? I've seen where some have cut the valve end off and welded a chamber to the cylinder.

I would like to machine a trailer ball to screw into the valve threads to mount the cylinder to a base plate trying to keep this build simple. But I'm skeptical of the powder charge laying right under the ball.

All suggestions would be welcome.

My background: Gun kid, gun guy. Reloader since 1979. Trained as a tool and diemaker. Farmer for 28 years. Have lathe, welder, bridgeport. My son and I built a golfball mortar in 2009.

Forget the trailer ball , mortars do not have knobs and neck.  Forget the tripod Stoke style mortar.  We know now that that if you use an antique ignition you can build a stokes style.  These tripod mounted bowling ball mortars have real reputation for being unstable and falling over when fired.

Stick with a trunnion style Mortar.  It is a bit more complex but a lot more stable and safer.

Here is a  drawing I did up real quick to illustrate how to do the powder chamber.



In the example above   a chamber is made from  of 4.5 inch diameter x 4.5 inch long piece of 1018 round stock and is bored 1.5 inches in diameter 3 inches deep.  The chamber is welded to a 4.5  trunnion bar of round stock.

The neck is cut off the tank.  The chamber and trunnion  are inserted through the bottom of the tank where neck was cut off  and the tank, trunnion  chamber are welded together.

Use a piece of seamless tubing to make a vent from out side the tank to the chamber.

[boiled_owl]

So far I have an oxygen bottle cut and a bowling ball, great start
What I'm trying to figure out is how to make the powder chamber, or is it necessary? I've seen where some have cut the valve end off and welded a chamber to the cylinder.

I would like to machine a trailer ball to screw into the valve threads to mount the cylinder to a base plate trying to keep this build simple. But I'm skeptical of the powder charge laying right under the ball.

All suggestions would be welcome.

My background: Gun kid, gun guy. Reloader since 1979. Trained as a tool and diemaker. Farmer for 28 years. Have lathe, welder, bridgeport. My son and I built a golfball mortar in 2009.

Forget the trailer ball , mortars do not have knobs and neck.  Forget the tripod Stoke style mortar.  We know now that that if you use an antique ignition you can build a stokes style.  These tripod mounted bowling ball mortars have real reputation for being unstable and falling over when fired.

Stick with a trunnion style Mortar.  It is a bit more complex but a lot more stable and safer.

Here is a  drawing I did up real quick to illustrate how to do the powder chamber.


In the example above   a chamber is made from  of 4.5 inch diameter x 4.5 inch long piece of 1018 round stock and is bored 1.5 inches in diameter 3 inches deep.  The chamber is welded to a 4.5  trunnion bar of round stock.

The neck is cut off the tank.  The chamber and trunnion  are inserted through the bottom of the tank where neck was cut off  and the tank, trunnion  chamber are welded together.

Use a piece of seamless tubing to make a vent from out side the tank to the chamber.

Dang was wanting to build a stokes style.

Going with your suggestion, what would you consider the limits on the size of the powder chamber IE charge capacity?

[Double D]

We have a set of stickies at the top of the board called safe loads and construction.  You will find guidelines for determining safe loads.

Using the guidlines and the example I gave above. the 1 1/2" chamber maximum recommended safe load is 500 grains of Fg or  Cannon grade. 

Chamber I drew above is the one that Southpaw uses in his mortar.

Ernie gets some good range out of his tube and he will be shooting it in the Mile blowing ball shoot.

[smokemjoe]

 If you look back I have pics. on here how to make one with the powder chamber fitted into the cly. Works great and easy to move. Joe