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Discussion Starter #1
Look at what I found today. Guess what my next project is going to be.

The best part is it was FREE!! :-D :-D WOO HOO :-D :-D

 

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CrufflerSteve said:
Its hard to tell scale but is it safe to assume you will be lofting ball balls in the near future?

Steve
That's the top half of an O2 cylinder that has a 8.75" ID. Just right for bowling balls. :-D

At the moment, I've got other things that take precedence (wife stuff) so it probably won't be launching anything real soon. The hard part (finding the right size cylinder) is done though. :)
 

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GGatLassen said:
What is the wall thickness?
At the torch cut, the steel is 1/4" thick. However, it gets slowly, but progressively, thicker as you go towards the neck. Near the top, I believe that it's almost 1". From carrying the thing, it's easy to tell that the valve end is definitely a LOT heaver (weight wise) than the body is.
 

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Unless the wall thickness around the bell end gets above 1/2", I would be reluctant to use that size cylinder as an artillery piece. You (or a subsequent owner) will always be tempted to launch the bowling balls to greater distance and those thin wall cylinders don't have much reserve strength.
 

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In the picture, the cylinder is shown just as I got it. At the torch cut the steel is 1/4". Since then, the cylinder has been cut to 18" in length and the valve adapter removed. Where the muzzle is now, the steel is 3/8" and, while I haven't measured it yet, the old Mark I Eyeball says that the top of the bell end is over 1/2" thick.

A 4.5" x 5" piece will be welded on that has a 2" x 2.5" powder chamber drilled into it. That puts a minimum of 1.25" of steel around the powder when it's touched off. As I'm sure you know, the chamber is where most of pressure needs to be contained. From what I've been able to find out, as the gas expands into the main body of the mortar the pressure drops very rapidly.

I've talked at length with Bill Tyrell (of Florida Bowling Ball Mortar fame) and am building mine the same way he did his. The plan is to shoot this thing for spectators and all of the shots need to be under 150 yards so the ball can be seen in flight and landing. That means the powder charges will be relatively light.
 
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