Bill Tyrrell sent these pictures and drawings of his bowling ball mortar.
The mortar is made from an old O2 tank. Bill says you need the one that is 29 1/8 inch in circumference. Cut it to about 18 inches. While cutting it also cut the valve stem off the back leaving a 4 inch flat for welding on the Chamber. The chamber Bill made is a piece or 4" x 5" round stock with 2" x 2 1/2" deep hole for the chamber.
Bill milled a flat and rigged a slap hammer on the side of the chamber . His nipple is made from 1/4-20 bolt
The Trunnion is a 2" solid round with a flat milled on the side to fit the bottom of the chamber. The trunnion is welded to the bottom of the chamber.
Ball warns not to make a carraige like his. the trunnion is too far back and the Mortar has a tendancy to turnover.
Here is a drawng from Bill for building the mortar. I have left it sideway so you can print it out and it will be large enough to read.
Great looking mortar Bill. I am wondering about the fireing mechanism and what type cap and nipple you use. Also what BP and how much is a typical shot?
Do you completely fill the powder chamber or use a filler or wad?
I made a "nipple" out of a 1/4"-20 bolt. The top is counter bored to accept a large rifle primer. It gas a saw kerf across the top of it to make it a little easier to expell the primer. There is a sketch of it in the items that Double D posted.
The firing mechanism is a slap hammer pulled by a lanyard. That shows up in the pictures fairly well.
You say in your letter that your chamber will hold 4 ozs of powder. Is that what you use?
In order to "enhance" the visual effect of firing your gun may I suggest you reduce your charge until you get impact say at 100 yards. It already looks like you have about 45 degrees elevation. On hard pack gound you will feel the impact of a bowling ball at 100 yards.
The old mortars and even the new modern ones range is controlled by the projection charge. Reduced charges were the norm in the old black powder mortars.
I can tell you that there is nothing more exciting than to fire a mortar and watch the projectile go up in the air. Watch projectile get smaller and smaller and smaller until it just becomes a speck that just seems to be hanging there. Then suddenly realizing the speck is getting larger and larger. Then becasue you have your head tilted back and are looking almost straight up get the feeling the speck is coming at you, only to impact in the pond 100 yards away, kicking up a geyser of water 25-30 feet high.
Warning. Always make sure you fire with the wind at your back. The Wind can and will blow you projectile back. Also a 25-30 ft column of water will soak you at 100 yards. :grin:
I can't wait to make one of these monsters! I cannot read the small dimension at the bottom of the primer holder.
Does the 4 oz of BP fill the cavity or do you use a filler or wad?
How well does the ball fit the barrel and do you use any patch or wad here?
Picked up one bowling ball yesterday at the "Waterfront Mission" for $2.85.