Author Topic: PRACTICE FOR BOWLING BALL MORTAR JOB (Read 2482 times)

jimwaits · « **on:** April 06, 2004, 06:35:24 PM »

After seeing Bill Tyrrell's Florida Bowling Ball Mortar on this site I really wanted to make one. I got hold of Bill who also lives in Florida and we met one day in Panama City. I got a hands on check out of his beautiful "Florida Bowling Ball Mortar". It's a real work of art. I have not had an opportunity to see it fired yet but am looking forward to that too.

I have several old oxygen cylinders and one of them measured close to the 29 1/8" circumference required and one measured exactly. I decided to take the one that was close and tear into making the mortar with it just for practice. A friend of mine came by and had a German made grinder, cut off tool "METABO" along with some Metabo cut off wheels. He whacked the nose off my oxygen cylinder before I could say Jack Frost!

I was so impressed that I went right in and got on the internet and ordered me one of those little jewels! ($200). It finally came in a week or so later and I got around to measuring and cutting off the cylinder at about 18 inches. So far everything went smooth. After the top was removed I ground it pretty smooth but did not open up the hole to two inches to match the hole in the soon to be powder chamber.

I have a 3 foot piece of five inch shaft which I finally got up on my seven inch metal cutting bandsaw and cut it off. Next I will put it in the lathe and square up the ends, round it off a bit and bore the powder chamber in it like the original Florida Bowling Ball Mortar of Bill's.

To mark the cylinder for cut-off I used an old six inch sanding belt for a
"wrap-a-round" and used it as a guide to cut the cylinder using my brand new "Metabo". That thing really does a great job and those little thin "Metabo" cut-off blades last forever!

After slicing off the 18 inch piece of the oxygen tank which at that point was a bit over a quarter inch thick, I had a beautiful looking start of a bowling ball mortar.

Only trouble is....the darn bowling ball won't go in the hole!! I guess I really knew all the time it would not fit but I wanted to get some practice before tackling the correct sized cylinder that I have.

Ready for the real Mcoy now and rarin to get started on it.

Here is a shot of the nose end of my cylinder....just cut off.

Next here is the cylinder with wraparound and mark on 18inch spot.

Here is the sad news....nole not big enough....

Fred · « **Reply #1 on:** April 08, 2004, 04:13:33 PM »

I was wondering if the O2 cly you practiced on had failed a hydrostatic test. If so it maybe slightly out of round and that is why the bowling ball might not have fit. I found this out the hard way and I was not practising.

I now have a CO2 cyl. that inspection showed had some rust inside when viewed with the valve off, since this cyl.. failed the visual inspection, I got it without it being hydrostaticed.

My plan is to tap the valve threads so a 2" trailer ball with a 1" shank, will screw in. This is then welded and a fuze vent drilled, a metal band around the tube with legs attached, load, light fuze, run, boooooooom.

I only got a far as cutting the cyl.. and then it was time for my annual bone graft since 2002 to my right leg as a result of a motorcycle acc. 4.5 yrs. ago, first graft was in 1999. Can't get much done in a wheel chair.

This winter I had planned on finishing my mt. howitzer carriage and building a carriage for my field howitzer and of course finishing the bowling ball motar. OH Well as they say "crap Happens"

Something for you BP guys to try. I full size coffee can (16oz or so) a hole large enough for cannon fuze on the side at the bottom, a film canister or so of BP spread across the bottom, insert fuze, a coffee filter spread over the BP, 2-3 cups of flour spread over the coffee filter, light fuze, run and boooom. Supposed to make a loud booooom, and shoot up a large flame. I have not tried this yet, but from what my friends say its worth the effort.

Remember "Do it to them before they do it to you"

jimwaits · « **Reply #2 on:** April 08, 2004, 06:10:21 PM »

No, I have just accumulated a few gas cylinders over the years. This one was due a hydro but was in good shape. It measured 28 1/2 inches around and I knew I measured the real Florida Bowling Ball Mortar that Bill Tyrrell made and it was 29 1/8inches. I did not see a ball go in his so I was not sure of how much windage it would have. I really expected that cylinder I cut to be too small.

My next cylinder is also a good one but I measure it to be within 1/16th inch of the same as Bill's mortar. I don't think you will have enough space for the powder with that trailer ball. Also it will be somewhat restricted.

My plan is to use a piece of five inch shaft about five or so inches long. I will drill and bore a 2 inch diameter hole about 2 1/2 inches deep for a powder chamber. The hole in the cylinder end will match up with the hole in the powder chamber. I will vee off the front edge to enable a good weld
to the cylinder. Then I expect to round off the rear part for better looks
and then machine a flat on the side of a two inch shaft which I will weld on the rear for a trunion.

I am planning on using an acme thread long bolt for an elevation adjustment. Also I am considering taking a piece of about half inch diameter rod and welding it to the outside of the barrel right at the front.
I will tack it on and then heat with a torch and bend it right around and tack as I go. Cut it off and then solid weld it around the mouth and grind it off to make it look better. That would give the mouth better strength.

Thanks for the tip on the coffee can deal....haven't seen a pound coffee can in a while but guess I can find one somewhere. I will try that!!
Might even improve on it by using a small oxygen cylinder or CO2 extingusher and making a plug for it with fuse hole in it. Would not throw any tin can parts around.
Come to think about it I could use the cylinder I just cut off that is too small for a bowling ball. I could cut if off shorter...say about a foot long and weld a thick plate with a fuse hole on the small end. Good for the fourth of July!

Will Jones · « **Reply #3 on:** April 09, 2004, 08:31:25 AM »

Jim it looks like were on the same journey

I have been following the forums on the b.b mortar very closely and last weekend decided to start the project..this below is a bearing lock/thrust washer that comes standard on most commercial shaft bearings.. I plan on using the set screws to lock the trunnion in place after the barrel is installed into the sled.. if i didn't use these i would have to turn the ends of the trunnions down on each end causing it to be weaker and having to keep to a set dimension.

This next pic is of the end of the powder chamber.. Notice that i 45ed the end like you were talking about for maximum weld i made the whole thing out of high quality H-13 tool steel.. It was all i could find around the shop....(shhh GOV>JOB)

This pic is of the side of the powder chamber i opt. to not cut 1/2" deep slot in the trunnion to accept the powder chamber.. I cut about .200 deep flat, i feel that at .200 it is enough and will provide max strength down force...(remember how a 12 gage kicked when you shot one for the first time, well this is a 15 pdr. with 3 oz of powder..)I chose to drill the the touch hole 2"down from the top to be a little closer to the center of the charge instead of at the very end.

The last pic is of the bottom of the trunnion.. i decided to drill and c-bore for a 1/4-20 s.h.c.s. this will hold every thing in relation (touch hole sq to the trunnion) for when it is welded. I opt. to make the trunnion 14" long instead of 12" this will allow for 10" of gap with 2" side walls. The barrel will be close to 9.125-9.200 wide... just incase my barrel doesn't sit above the sled..

Best of luck Will Jones.

Double D · « **Reply #4 on:** April 09, 2004, 11:08:25 AM »

Will,

I don't know if you picture posting site allows links or not. Just copying the page they are on won't work with your site as it appear you have to log in first.

Try right clicking on the picture and then click on properties. When the properties window opens copy and paste in the url for the pictures. i don't think that will work with WebPhotos.

Please! I wanna see what you are doing.

Cat Whisperer · « **Reply #5 on:** April 09, 2004, 04:32:25 PM »

Just a thought:

Take a short section of the same cylinder - say about as long as it is in diameter or thereabouts.

Grease the inside well and place it on a greased board (or cookie sheet) and fill with concrete. When the concrete sets/dries it will shrink just slightly - it's not yet up to full strength (takes several days), but it can be easily pushed out of the mould.

Knock off the rough edges and you have a custom fit cast boolet.

(re-mesh would be a good idea too)

jimwaits · « **Reply #6 on:** April 09, 2004, 06:00:56 PM »

Don't know if that is good idea or not. The cast projectile would be a perfect cylinder and would not be rounded off on the end like the bowling ball is. This would leave a large space at the bottom of the mortar and I don't think that works too good does it?

Cat Whisperer · « **Reply #7 on:** April 10, 2004, 01:49:24 AM »

I don't think it would matter at all. I use (since I made it to that caliber) 4" pvc pipe filled with concrete. It's 4.50" in diameter and I have a bore that is 4.55" giving 50 thousands (on the diameter) clearance or 'windage'. That's the only thing I'd worry about - perphaps a layer or two of craft paper around the inside of the mould to ensure a little bit of clearance. More clearance isn't terribly bad, just reduces the velocity. I've even used thejuice cans that are 4-1/4" in diameter.

jimwaits · « **Reply #8 on:** April 10, 2004, 02:43:42 AM »

Well, it sounds okay. I was a bit concerned not with the windage which I can take care of with paper in the mold but the great cavity at the bottom of the rounded end of the cylinder. From where the molded bullet stops on down to the powder chamber would be a giant cavity with nothing in it.
Where are you DD?

Double D · « **Reply #9 on:** April 10, 2004, 03:33:12 AM »

Catwhisperer is right don't worry about the space at the bottom. He has a lot more experience in that than I do.

In the mortar the part where the projectile is is just an expansion chamber. You might even look around for some pvc that will slip down that cylinder. Just make sure you have windage.

jimwaits · « **Reply #10 on:** April 11, 2004, 04:37:58 PM »

Hello DD and the Cat.....a buddy of mine gave me a good idea and I want to run it by you two guys. He suggested making a metal pin that would fit the thumb hole on a bowling ball. Weld a bump on each side of it and file or grind it off so it would make a couple small blades. Bump it into the ball then chuck the ball in the lathe. and push the tail stock against it hard....seating the blades to help hold the ball when it turns.
I only need to remove less than a quarter inch to have plenty windage in my too small oxygen cylinder. Don't try to round the ball just remove enough to make a match for the barrel leaving plenty of windage.

Do you think this would be safe or would there be a tendance for the ball to roll in the barrel and lock up or would the band around the narrowed up ball tend to be a guide for the projectile. Seems like it would be better than a cylinder made out of concrete as someone suggested.

Will Jones · « **Reply #11 on:** April 11, 2004, 09:36:38 PM »

I found another page that would allow me to host photos and externally view them.. buy the only catch is it only allows 5mb of download in a day.. do you guys know of any sites that dont have that limit and are easy and free?

Anyway.. I have found a 02 cyl. at a scrap yard and it was the only one of that type there.. After exausting my efforts of going to welding shops , which directed me to welding gas companies, which gave me a funny look when i asked for junk 02 tanks (they weren't very helpfull) which led me to a junk yard. The tank measures 8.530 on inside diameter, with a .275 wall thickness.. I have a 16 pound bowling ball which just almost fit.. The ball measures with digital calipers 8.590...Either i could cut the Length of the barrel from say 18" to say 10". Weld the powder chamber on there as sq. as possible, then chuck up on the powder chamber indicate the bore in true, and bore out say .100 it could work.

I dont see that the cyl has to be, twice the length of the projectile,(check out the coke can mortar on cannon mania, there is at least an inch of can sticking out of the barrel) sure it would get a little better accuracy , but as long as the projectile is able to fit in the barrel below flush it should work fine... were talking a smooth bore with a least .05 to .1 clearance aroud the ball not a sharp shooter ,+ those guys that shoot the 100lb. anvil 1200 feet straight up out of site dont have a barrel. All they use is a really thick cast block with a powder chamber that holds about 1lb. of powder...i can see having some what of a barrel to deflect the blast foward and not out the side.. but the volume of the barrel compared to the power chamber is like 10:1 , like what some one wrote in a previous forum.. the cyl. is more or less a runway for the ball, not needing the durability or strength as the powder chamber would.

since my ball is 8.590 in diameter, .060 from fitting, being the largest weight of bowling balls and the only one i have checked, I'm wondering if a different brand or lighter weight would differ much in size?

See ya Will The pyro

Cat Whisperer · « **Reply #12 on:** April 12, 2004, 01:02:18 AM »

Jim -

ONLY one way would I put a spherical projo down the tube if it were only trimmed to fit in a narrow band.

The problem is that in contacting the side of the tube, the ball will roll slightly - and wedge.

The gauges used by arsenals (Civil war era) were simply a handle and a ring of flat sheetmetal with the appropriate size hole in it. To pass the sphere must pass in ALL directions.

SO, consider bolting a disk onto the ball. That keeps the thing from rolling. Then trim the sphere so it will clear.

NitroSteel · « **Reply #13 on:** April 12, 2004, 05:23:43 AM »

I went by the Welding Shops in town today and they said that they were unable to sell or give away any of the tanks that they were unable to refill for legal reasons. However one of the owners sent me to a junk yard that did have several tanks. I was unable to find one that measured 29-1/8", but did go ahead and get one that was 28-5/8. I haven't cut it yet, and realize that a bowling ball probably will not fit. I do plan to cut it and make a mortar out of it, but I'm not sure what to shoot?

What should I shoot? I don't have any way to bore the hole bigger or to cut down the bowling ball to a smaller diameter. I know that others have run into this same problem.... I don't think I'll be able to find the correct size tank (at least not locally), but I want to make a mortar to shoot something, so again what kind of projectile can I shoot? Can I make something? What have ya'll done or planning on doing? Concrete cast? Make a wooden ball (how)? Shoot gallon bleach jugs full of concrete?

Thanks,

NitroSteel

Double D · « **Reply #14 on:** April 13, 2004, 05:11:35 PM »

It would seem to me the size tank you need is a 337cuft tank.
http://www.weldingsupply.net/oxygen.htm

jimwaits · « **Reply #15 on:** April 14, 2004, 05:36:07 PM »

I carefully measured the Florida Bowling Ball Mortar and it was 29 1/8inches in circumference. That would be 29.125". I also have one I believe is close to this. I will measure it tomorrow. The 337 Cu ft one you
showed has a circ of 29.0598" and don't know for sure if that would go or not!
I think there are lots of mfg and little standards in bottles.

Mike Scott · « **Reply #16 on:** April 17, 2004, 11:58:36 AM »

outside circumference? I can get one of these if it would be OK.

Will Jones · « **Reply #17 on:** April 17, 2004, 04:11:25 PM »

finally got my pictures to post indefinitely sorry about the confusion..Check them out up top....WILL

jimwaits · « **Reply #18 on:** April 17, 2004, 04:38:21 PM »

Yes, Mike, 29 1/8 inch outside circumference is what the real Florida Bowling Ball Mortar is. I measured it myself.

Will, those are beautiful shots and your ideas seem sound to me. Be sure and put more shots up as you progress along. I am very much interested also in what you use for loads etc.

jimwaits · « **Reply #19 on:** April 23, 2004, 03:17:27 PM »

Well, I got the 29 1/8inch cylinder cut off at 18inches overall. The nose was cut off leaving a nice four inch flat. The bowling balls fit nicely and have a bit of windage as necessary.
I put the chunk of five inch shaft in the lathe and trued it up and faced
the end. Ready to start drilling and boring it for a powder chamber.
Got a few pictures but gonna wait and put them all up when I get the thing together. Progress is slow.

Cat Whisperer · « **Reply #20 on:** April 23, 2004, 03:24:53 PM »

That's proof that the 29-1/8 OC is it!

Take plenty of pictures. Sometimes it's good to go slow, it often brings out a better design in the end.

Keep us posted!

NitroSteel · « **Reply #21 on:** April 23, 2004, 11:32:59 PM »

Well, I went and dug through the junkyard again- - several different piles yesterday and found two tanks that will have to work. One is 29-1/2 (this is the one I got), the other is 29-3/4. I figure that I may have a little bit more windage that the original "Florida Bowling Ball Mortar", but feel I should be okay.

I do know that it is a chore to cut these tanks in half and don't want to go through it again if this is going to be too much windage. Let me know what ya'll think.

NitroSteel

Double D · « **Reply #22 on:** April 23, 2004, 11:43:39 PM »

Get em windage is fine, these are only launchers!

Cat Whisperer · « **Reply #23 on:** April 24, 2004, 01:13:52 AM »

Windage - my first thought is 'passing gas' - well, I guess it's literally true.

Extra is safe, but will cut down a little on range. It just takes a little more powder and/or length of tube.

On my 4.55" bore diameter mortar I use 4.50" That's .050 clearance on the diameter, which works well.

The juice cans (46 fl oz) are 4.24" in diameter also work. As I said, a little more powder or little less range.

If you drill a hole in the side (probably have to own it at that point) you could measure the inside diameter with a wire. That would give you a good dimension on which to make the decision to cut or not.

NitroSteel · « **Reply #24 on:** April 24, 2004, 02:27:35 AM »

Thanks for the help guys!

I will be cutting today.

In regards to the powder chamber: I do not have access to a machine shop, what is the best (safe, simplest, easiest and cheapest) way to make a powder chamber. I have a wheel grinder, and a MIG and stick welder and drill press. What should I use for a powder chamber? How should I bore the hole.

Thanks again,

NitroSteel

jimwaits · « **Reply #25 on:** April 24, 2004, 04:06:34 AM »

If you could find one of those six inch METABO grinders and a Metabo cut-off disk which is only about a sixteenth of an inch thick you can cut that cylinder off in fifteen minutes with no trouble. Maybe another fifteen minutes to cut off the neck. Two blades should do it.
If they get many of those cylinders at your junk yard I might keep looking for a while to find a 29 1/8inch one.
You are going to need a powder chamber about four inches in diameter and about five inches long with a two inch hole in one end about two and a half inches deep.....see Florida Bowling Ball this forum.... I don't see any way for you to do that without a lathe or a great big drill press. Maybe you have a local machine shop which could drill a two inch hole for you for a reasonable price. A little more time envolved if he has to drill it and then bore it out to proper size but maybe he will have a two inch bit.