Author Topic: Bowling Ball Mortar (Read 1823 times)

Fred · « **on:** September 12, 2003, 08:52:52 PM »

One should not be up at this hour "thinking" so this may be a little inchorenent. From what I have been reading here and elsewhere one can use a welding gas cly. for a barrel. My questilon is what kind of gas, oxygen, co2, argon,??? 2/ what does the inside dia. of the cly have to be for a bowling ball tube? 3/ I have read that a 2" trailer ball can be threaded into the top of the cly. once the 1" threads have been rethreaded from a taper to striaght. Once this is done is there enough space left for a powder chamber recessed under the ball when it is at the bottom of the tube? 4/ what dia. should the vent hole be? and what angle? should the vent hole end up near the top, middle or bottom ot the powder chamber? 5/ how to make and attach trunions to the tube for a wooden base?

It sounds kindka of simple, find an old welding cly. cut it off, screw in a trailer hitch ball, put a band around the barrel and attach some legs, drill a hole close to the bottom of the tube, dump in some powder, drop in the bowling ball, light a match and boooooommjmmm.

Since the bowling ball mortar seems a breeze to make what other sizes of high pressure gas cly. would make a smaller mortar, beer can size, small coffee can size, 4"-6" range. anyone have any ideas?

Fred.........................

Do it to them-Before they do it to you!!!!!!!!

Cat Whisperer · « **Reply #1 on:** September 13, 2003, 01:57:41 AM »

Let me shed a little light that others will undoubtedly suppliment.

Q1. Compressed gas cylinders come in standard sizes, painted for the gas they are to contain. They are pressure tested and so date stamped and serial numbered. The size for the bowling balls is 80 cubic feet.

Q2. The ID of the cylinder should be slightly larger than the bowling ball, obviously for clearance for the obvious reason. Bowling balls are regulated in size as well (DD posted something on that in our reference section) If you take the maximum and minimum circumferences of the bowling balls you can convert that to maximum and minimum diameters easlily. Then add your clearance. Not having run the calculations recently I seem to remember something about 8-1/8 or so diameter for the bowling ball.

Q3,4 IF IT WERE ME, (your mileage may vary) I would build an adapter for the trailer hitch that would thread into the threaded hole left from removing the valve AND run the touch hole through it. That leaves the cylinder intact, but would require several inches of fuse. I'd make the fuse hole at most 1/4" - that allows standard 7/32 diameter blasting fuse (if you can get it) as well as the smaller currently available cannon fuse as well as a small brush for cleaning. I would place the charge in the neck without further modification or cutting of the cylinder.

Q5 Look at the pictures posted for attaching trunions. Commonly done is a band around the tube towards the top with two lugs at about 90 degrees from eachother to attach to legs OR two lugs slightly closer together to attach to a traverse and elevation mechanism which would be attached to the two legs.

Fixed angle is OK with the mortar. Once you figure your range (most often limited by the place where you shoot) adjusting the point of impact is much easier by adjusting powder charge. Get fancy with the t&e mechanism if you want to.

Double D · « **Reply #2 on:** September 13, 2003, 02:45:30 AM »

Here is a link specifically to Mortar safety, and structural requirments. Take a look at them as they serve to provide guidlines for construction.

http://www2.control.com/%7Eemoore/AAA/mrt.html

From those safety rules notice: "Barrel length shall not exceed 2 times the projectile length, while projectile length shall not exceed 3 times the bore diameter"

Fred · « **Reply #3 on:** September 13, 2003, 04:20:51 AM »

Thanks DD for the quick repley, don't know why I'm up this early, except that I'm hungry.

I don't quite understand what you mean by making an adapter for the trailer hitch ball for the fuse? You will have to explain it in simpler terms, to bad one cann't draw pictures on these e-mails.

Ref. trunions I was referring to the kind on coastal mortars, the trunions mounted on the end or near the end of the mortar, which are mounted in carriages.

Maybe its because its early and I went to bed late, but I don't understand the barrel length 2x's the length and projectile length no more than 3x's the bore dia.. My math makes the bowling ball dia. 8.605, so 2x's that is 17.21 in for the barrell (tube) and since the height of a bowling ball is also its dia. that would be 8.605 and the bore dia. a lilttle larger than that. So my math again shows the projectile length (bowling ball) 8.605 and times three is 25.815 inches (8.605x3=25.815). wouldn't this make the length of the projectile over 8.605" longer than the barrel(tube)?

The pictures posted 0n 2-28-03 by Big Richard Hertzer show bowling ball mortars make by Bob McBride with tubes looking longer than 17"

Oops gotta go before I miss breakfest

Fred>>>>>>>>>>>>>>>>>>>>>..

Fred · « **Reply #4 on:** September 13, 2003, 04:31:39 AM »

Just to darn early when getting to bed so dam late.

I want to apologise for gettilng DD mixed up with Cat Wisker.

To Cat Wisker thanks for the information.

To DD I'm familiar with The American Artillery Assoc. and have both thier Cannon and mortar regulations printed and in the limber box.

FRED..................................

Double D · « **Reply #5 on:** September 13, 2003, 05:06:52 AM »

Fred,

I think they are talking about using a projectile other than a ball, say a cylinder.

If you use a bowling ball the tube should 17.21 long.

If you use a cylinder shaped projectile the length of that projectile should be no more that 3 time the bore diameter. So using an high pressure cylinder that is 8.6 inch in diameter the longest suggested projectile would be 25.6 inches. Tha means 8.39 inch is going to be sticking out of the muzzle of you mortar designed for a bowling ball.

Cat Whisperer · « **Reply #6 on:** September 13, 2003, 01:26:16 PM »

fred -
No offense taken by anyone. As I think about it, if the threaded hole is much smaller than the threads of the ball, I'd just turn them down and rethread to fit.

So, I'd drill a hole (through the axis) of the hitch ball about 1/2 to 2/3 the way through, then drill another at an angle from the outside of the hitch ball that would intersect, such that a fuse (and cleaning brush) could be run from the outside (near the ball) into the center and up into the cylinder.

Now for trunions, of the style that would mount mid tube and around which the whole tube would swivel - haven't seen any done that way. Sounds like a fun design project.