bowling ball mortar

[Cal.8.60]

Hello! It's comforting to know that there are other "nuts" out there! I'm new to this board. it looks like one of the best I've seen, a lot of good info with a very positive tone!  

The drawings on Bill Tyrrell's mortar are great! I,ve tried to run some figures on it with barlows formula and my "wee-little-brain" hurts.

It appears the powder chamber if made from 4140 would be good for 45,000psi ultimate bust presssure,allowable working pressure of 32,400psi and minimum yield of 30,000ps i The same formula run on the oxygen cylinder is under 4900psi for ultimate burst pressure! Are the pressures in the "barrel" reduced that much

Just being over cautious before I build! Thanks you guys

[Lead pot]

Talking about bowling ball canons,check this out.

http://www.hatchergun.com/Cannons/BBM_Its_Dark.JPG
http://www.hatchergun.com/Cannons/BB_Mortar_Justin_2.JPG
Kurt

[Cat Whisperer]

Hello! It's comforting to know that there are other "nuts" out there! I'm new to this board. it looks like one of the best I've seen, a lot of good info with a very positive tone!  

The drawings on Bill Tyrrell's mortar are great! I,ve tried to run some figures on it with barlows formula and my "wee-little-brain" hurts.

It appears the powder chamber if made from 4140 would be good for 45,000psi ultimate bust presssure,allowable working pressure of 32,400psi and minimum yield of 30,000ps i The same formula run on the oxygen cylinder is under 4900psi for ultimate burst pressure! Are the pressures in the "barrel" reduced that much

Just being over cautious before I build! Thanks you guys

Cal.8.60 -

Welcome!

You've named a few things near and dear - safety and 'warm and positive tone'.  Thanks!

Educate us on Barlow's formula!  Sounds like you're taking an engineering approach to design.  That's good - what ever it takes to ensure that you're lighting the fuse to a cannon/mortar and not a bomb.

Thanks,

[Cal.8.60]

Sorry, Barlows formula is used in the pipe and tube industry for figuring burst pressure,etc. A Goggle search with the term "Barlow's Formula"should give several places that even have automatic calculate!

[Soot Sucker]

Hello Cal.8.60,

Welcome. It really is a great board. Everyone is civil towards each other. Never a negative tone, and someone or many are always quick to answer a question or share some info.

It's a fine board,

Again...Welcome,
S.S.
(Dave)

[Cat Whisperer]

Sorry, Barlows formula is used in the pipe and tube industry for figuring burst pressure,etc. A Goggle search with the term "Barlow's Formula"should give several places that even have automatic calculate!

That was my guess - that it had something to do with hoop strength.  A good place to start, knowing that there are other variables influencing - like welds, varying form and  other features.

[Lead pot]

Here are some more fine workes of art.

http://www.hatchergun.com/blkpwdrcannon.htm
Kurt.

[Cal.8.60]

Thanks Kurt!  I made contact with Dan at Hatcher, seems like a great guy! I,m planning on attending his shoot in casper in june. He hasn't set an exact date yet.

[w a tyrrell]

Thanks for the compliment on the drawings.  I don't recall if I made the change or not, but the trunnion needs to be 13 1/2" long if you use full 2" wood for the mount.

I too was concerned about the ability of the cylinder to take the pressure.  It's awfully thin!  I think that there are a couple of things helping it:  the chamber is where all of the action is; once the ball starts to move the volume and consequential decrease in pressure increases rapidly. Obviously the windage, which is ample helps, too.

Someone reported using 12 oz. of powder and two balls as a proof load and the barrel stood up to it.  Nonetheless, it would be interesting to put a pressure sensor of some sort down near the chamber and find out what is really going on.

Best Wishes,  Bill Tyrrell

[SLEEPY BEEPER]

It should be noted that an O2 tank is a little over 1/4 inch when cut open at the center. It is not the same thickness over all. This is the thinnest area. The valve end is almost 1 inch thick. This thickness in the top is what saves you. For both welding and handling the pressure until the gas expands into the full barrel. If you are going to look at problems. You have to be looking at the weld. When I welded mine. I welded everything including trunnion one shot. Everything got hot enough that it took 2 hours to cool to the point you could touch it. You do not want to make any small welds on something like this. This will cause stress that leads to failure.