A Florida Bowling ball mortar

[Double D]

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.

.

Thanks Bill for sharing it with us

[Hermit]

Nice, Love the shots caught during firing. :grin:  Hermit

[w a tyrrell]

Dear Double D:

The pictures, text and sketch look great.  I do my best to answer what questions people may have.

Best Wishes, Bill

[Double D]

Bill,

I have two questions.

Do you have any pictures of the splash when the ball hit the water.


Do bowling balls float?

[w a tyrrell]

Dear Double D,

No, we don't have any pictures of splash down.  It would probably take a telephoto lens to capture it due to the distance.  It is a big splash.

Most balls sink.  We had one that floated.  I think that there are some 8 pound balls and since their volume calculates at a little over a gallon those would be the floaters.

Best wishes,  Bill

[jimwaits]

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?

[w a tyrrell]

Dear Jim,

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.

The charge is about 1500 grains of FG.

Take Care,  Bill

[Double D]

Bill,

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:

[jimwaits]

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.

[w a tyrrell]

Dear Jim,

I you are going to build one of these, I would like to talk to you and also snail mail you some more of the details on mine.  I am at 772 223-1681.

Sincerely,

Bill

[NitroSteel]

To me, this was the post that started it all.  I couldn't believe this thing when I saw it, so instead of just talking about it, I actually went out and built one.

As I read through the cannon and mortar rules I got to thinking about the wall thickness on this mortar (only 1" with a 2" chamber).  Is this thick enough to be safe, especially when firing a projectile weighing up to 16 or so pounds?  Mine has (at least so far) proven to be safe, it's probably shot close to 30 pounds of powder and I keep both of the local bowling alleys and every garage sale free of old balls.  Upon beginning to read about building a golf ball cannon/punt gun I got to thinking about the wall thickness on the chamber of this mortar (and mine is EXACTLY like it, only with a much sturdier carriage - and I'm not knocking this one). 

I want to do what is right and what is safe, But why in the world should I make the wall thickness on my golf ball cannon (with only a 1.75" bore - shooting only a 4 to 16 ounce projectile ) an inch thicker than my bowling ball cannon?  I realize that cannons and mortars operate on different rules, but I'm not talking about the "barrel" of the mortar, I'm talking about the powder chamber which to my understanding is the bore.

I don't mean to dispute the rules of cannon building, but my bowling ball mortar is on wheels.  The punt gun has to be carried.  Is the bowling ball mortar underbuilt?  Am I overlooking something?  I really think these are valid questions and worthy of bringing back an old topic.  I've been shooting my BB mortar for about 2 years now, but I still consider myself a newbie.  I always want to make sure I have a good understanding before I start on a new project and especially before I light a fuse.

I appreciate all of the help, information and insight you guys offer.  I can't tell you how much I enjoy reading the forums.

Thank you again for your help.

NitroSteel

[Cat Whisperer]

As we go through life we learn more - hopefully.

Let's review some basic principles of powder chamber design - which we've mentioned from time to time here.

The thickness of the metal around the powder chamber should be equal or greater than the diameter of the chamber (in all directions).

A quality steel should be used - mild steels are good.

With some alloys (4130/4140 and others) welding requires preheating and slow cooling to prevent cracking AND should be done by professional CERTIFIED welders.

Welding in areas where combustion products are present is NOT acceptable - porosity and corosion over time will cause failures.  This is the reason SEAMLESS tubing for liners is a requirement.

Rounding the inside corners  -  or a spherical bottom of the chamber  -  is very good as it eliminates 'stress risers' - locations where stress is concentrated.

Tapering the powder chamber also is a good way of making it stronger.

The walls of the mortar can be much thinner because the maximum pressures of the powder burning are concentrated in the powder chamber and then are reduced greatly.  Coehorn took advantage of this in the 1700's.

There are general rules for construction outlined by AAA and N-SSA that have been successfully employed for years.

Special attention around the fuse hole should be taken to preclude corrosion when using a liner.

Prudent loading is good. 

There are good and bad designs.  Probably everything out there can be improved in some way. 

To sum it up four things must happen to keep safe:  good design, good fabrication, good materials and good/prudent loading practices.

[Cat Whisperer]

Let me add, my first mortar was in beer-can caliber.  I'd found a piece of hot-rolled steel - hard, raw from the foundary.  Wore out a complete cutter bit cutting the hard surface off the outside.  Didn't have a boring bar, so I used a long 3/4" bit to drill first and then clamping it in the tool holder using it for a boring bar.  It took months to make (a few hours at time) after hours where I taught.  The powder chamber I cut (with the 3/4" bit) was tapered.  Polished it up and it looked good - simple straight confederate design except for the 1964 MGB flywheel I used for a baseplate.  Thickness of metal at least that of the powder chamber daimeter all the way around.  Took it to the plating factory and had it chromed!  That was back in 1974-75.  Fired it on July 4th 1975 - (the 200th anniverasry of the shot heard round the world.

I build them differently now.  Better in many ways, but I'll NEVER sell my first one.

[Double D]

Check the dates on that post.  There was a learning curve going on back then.  We now cite the N-SSA and AA standards for safety.   

If you choose to not use those standards that is up to you. 

Bill's powder chamber is to small and should be  6 in. minimum.

[NitroSteel]

Thank you.  I'm was just making sure that I am thinking correctly as far as the basic principals being the same.  Point taken, I didn't realize that the methods/learning curve had changed so much in the last couple of years.

[Cat Whisperer]

Thank you.  I'm was just making sure that I am thinking correctly as far as the basic principals being the same.  Point taken, I didn't realize that the methods/learning curve had changed so much in the last couple of years.

Not only that, you don't hear me talking about the 'cannons' I made as a teenager of iron pipe using (fortunately) home-made blackpowder.  I KNEW for YEARS that I'd never live to see age 21!

[NitroSteel]

Cat Whisperer,

I did the same thing.  Everything from potato guns using thin PVC pipe and ether, to making firecrackers out of homemade gunpowder, and shooting D cell batteries out of conduit using lighter fluid as propellent.  Actually made a "potato gun" one time out of 2.5" PVC (was only available at one mobile home store at the time) that shot tennis balls, to make a long story short, nothing good came of that...

I don't know how my parents slept at night.  I'm just glad I lived.  I always swore that someday I'd have a legitamate cannon.  The bowling ball mortar is the coolest "toy" ever and I don't have to hide when I light the fuse.