Author Topic: bowling ball mortar question (Read 1459 times)

dirtdobber1919a4 · « **on:** September 21, 2009, 08:06:02 AM »

im am very interested in building a bowling ball mortar, but im having trouble finding a compressed gas tank that is big enough. does anyone know what size tank i need? i thought i need an "L" size tank. the folks at the welding supply shop look at me like i was crazy when i told them what size tank i needed. so any help would be greatly appreciated.

Cat Whisperer · « **Reply #1 on:** September 21, 2009, 09:03:48 AM »

dirtdobber1919a4 --

I'll have to look it up. The ID should be about 8-1/4" which translates to an outside circumfrence of 20 something inches. I'll get to it tonight if someone else doesn't pitch in with the real numbers.

WELCOME to the board too!

BoomLover · « **Reply #2 on:** September 21, 2009, 02:39:10 PM »

Welcome to the board, also, dirtdobber1919a4! Back in the old days, (2004), there was a posting which had the title "Florida Bowling Ball Mortar", if you look that one up here on the forum, it details exactly which tank you need. BoomLover

GGaskill · « **Reply #3 on:** September 21, 2009, 03:00:16 PM »

Actually, unmodified bowling balls are about 8.6" in diameter.

dirtdobber1919a4 · « **Reply #4 on:** September 21, 2009, 06:39:29 PM »

i have one tank now. when i cut the bottom off the ID was 8 1/4. it isnt big enough.aponmuch looking on the web, i found that i need one with the ID of 8 3/4. i thought that would be an :L: size tank, but the local welding supply shops hae no idea what an :L: size ank is. everything they have is measured in cubic feet. so dont know where to find how many cubic feet will be the correct size tank.

GGaskill · « **Reply #5 on:** September 21, 2009, 08:46:32 PM »

Here is a table of tank sizes at wikipedia.

Double D · « **Reply #6 on:** September 22, 2009, 04:09:33 AM »

http://www.cousesteel.com/AndysPlace/CylinderSize.html

BoomLover · « **Reply #7 on:** September 22, 2009, 05:24:27 AM »

dirtdobber1919a4, I looked up the old posting and PM'd it to you, read the whole thing, and if you decide to build one, over build for safety! Always! We want you around as a forum member for a long time! There are other postings on bowling ball mortars and cannons, look them up and check them out also. Study them, ask questions, there are very knowledgable people on this forum! Assemble as much info as you can before you begin to build! BoomLover

SLEEPY BEEPER · « **Reply #8 on:** September 22, 2009, 07:15:10 AM »

If you can find a tank that measures 29 3/8 inches around the outside. You probably have the right one.

NitroSteel · « **Reply #9 on:** September 22, 2009, 02:49:52 PM »

29-5/8 diameter I believe. I've got a spare one in the shop already cut if you are interested. I know it is the right size...

NitroSteel · « **Reply #10 on:** September 22, 2009, 02:51:24 PM »

Circumference I meant, not diameter...

Double D · « **Reply #11 on:** September 22, 2009, 02:53:29 PM »

If you click on modifiy you can fix it.

GGaskill · « **Reply #12 on:** September 22, 2009, 07:07:37 PM »

29.375" circumference will give you about 3/8" wall thickness. 29.625" circumference will give about .41" wall thickness. If they are 8 5/8" ID.

dirtdobber1919a4 · « **Reply #13 on:** September 25, 2009, 07:54:40 PM »

yes i would be very interested in a tank if you know it will work. just let me know how much you want for it and how long it is.

dougrunnels · « **Reply #14 on:** September 27, 2009, 08:43:00 PM »

Mine is 29 3/8" around. I built mine patterned after "Florida Bowling Ball Mortar". I could post some pics if anyone is interested altho I never finished and painted it. I could also get the #'s off the tank if needed. I cut 2 tanks before I found one that a bowling ball would fit in. Both were smaller in diameter and circumference than the one I used. I believe I posted details on how I built it before on this forum and you can probably search for it. It's been shooting for 2 years and hasn't blown up yet. In fact, I shot it today. I still get excited when it goes off and the16 lb. bowling ball almost disappears in the sky and hearing the ball whisteling and the thump when it lands. I still have the lower half of my tank I would let someone have to build their own mortar, IF I'm convinced they will build it properly. Near Houston.

BoomLover · « **Reply #15 on:** September 30, 2009, 10:51:50 AM »

I am building one out of a scuba tank. A Folgers coffee can (Red Plastic) fits perfect. Will fill with concrete, (coffee can, not the barrel!) and start testing! How long is the piece you have left, Dougrunnels? Did you make a Mortar or a Cannon out of what you used? Can you post some pics anyway? If not painted, no problem, just call it a work in constant progress! The Flordia BB Mortar is a nice piece, but I agree with Double D, needs to have the powder chamber built with thicker walls. BoomLover

dougrunnels · « **Reply #16 on:** October 04, 2009, 05:18:45 PM »

BoomLover,
FYI the circumference of the cylinder = 29 3/8" aprox. measuring with a metal tape
ID = aprox 8.75" my venier caliper would not go that wide
Wall thickness = 0.290"
DOT-3AA2400 stamped on the cylinder if that means anything to anybodyI now have pics of it painted.
I also have pics of all the #'s on the cylinder.
Hmmm, how to post pics here?

Double D · « **Reply #17 on:** October 04, 2009, 05:38:31 PM »

That DOT marks seems to be the critical number. If you click on the link http://www.cousesteel.com/AndysPlace/CylinderSize.html that I posted up thread you will see this is a 300 CF high pressure tank from Taylor Wharton.

dougrunnels · « **Reply #18 on:** October 04, 2009, 10:22:49 PM »

Here are pics of painting my mortar AND views of the stampings on my tank.

ENJOY

http://www.flickr.com/photos/74433133@N00/sets/72157622518535322/detail/

dougrunnels · « **Reply #19 on:** October 04, 2009, 10:38:41 PM »

After painting it all red I thought a flag pattern mite be better, but I can't figure out how to make it with the red .
US flag would be great, BUT the Texas flag would be better!
What do U think? And how would I configure it?

Double D · « **Reply #20 on:** October 05, 2009, 03:47:22 AM »

What is the ID and OD of you powder chamber. It looks too thin walled. Walls should be the same thickness as diameter ID.

1Southpaw · « **Reply #21 on:** October 05, 2009, 04:42:27 AM »

to paint the one in the avatar . took a week or so as it had to dry between coats to keep tape from pulling paint.

dougrunnels · « **Reply #22 on:** October 05, 2009, 10:51:39 PM »

DOUBLE D,

ref my original post about this mortar:

After the 2nd cylinder I cut in half, I found one that would accept a bowling ball. The circumference measured aprox. 27 7/8" . Windage is about 1/4". I can do more measurements if anyone is interested. I cut the valve from the cylinder with a band saw and "faced" the end untill it was about 3.5"flat with a hole of about 1.5". Using a piece of 1018 cold rollled steel, 4" dia X 5" long, I bored a "chamber" 1.780" X 2.548" deep, and faced it leaving a"insert" into the O2 cylinder aprox. 0.4" deep, press fitted. We then welded the chamber to the cylinder With TIG welding.

Probably what concerns you is the pic of the inside of the bore. It shows the "step'd" down diameter where it was pressed into the O2 cyl. I don't remember if you commented on it before, but what do you think?
I have shot it, hmm, maybe 50 times now. Mostly with charges the exceed the chamber volume. And mostly with FFg, but have even used FFFg when it was handy.

Double D · « **Reply #23 on:** October 06, 2009, 05:11:52 AM »

Chamber walls are thinner than recommended by safety guidelines. The steel you used is strong enough, your walls are too thin. Your margin of safety has been reduced with under sized chamber walls, and the use FFG and FFFg reduces you safety margin even more.

When Matt Switilik brings out his next edition of his book The More complete Cannoneer, get a copy. Switlik's book has a very interesting chapter on black powder pressures. In that chapter using pressure guages Switlik tested Cannon grade and Fg. In his test Switlik found that equal volumes of the faster burning Fg gave a 40% increase in pressure over Cannon Grade for no increase in velocity.

FFg is faster burning and develops higher pressures than an equal volume Fg. FFFg is faster burning than FFG and develops higher pressures than equal volumes of FFG.

The fact that you have fired the gun with FFg and FFFg without incidence is meaningless.