Need advice on 13 inch mortar I'm building

[entsminger]

I know there is no easy answer to my questions,  but being it's been bugging me for some time now I thought I'd ask you guys what you think. I am building a replica , non-firing, 13 inch 1861 seacost mortar from an old large propane tank (can't afford Paulson's wonderfull reproduction).The origional diameter of the 13 inch mortar is 43 inches. My propane tank is a tad over 40 inches. I would very much like to have my home made replica to be as close to origional specs ( for looks sake) but at the same time I don't know if it's worth the much extra effort to expand the tank to the proper 43 inches? I thought I might slice the hemispherical tank end ( and barrel seperately) about 6 times and expand it some 3/8 inch each cut to expand it to the proper diameter and weld it back together. I weld well and have a plazma cutter to make the cuts etc. My question to you is...By cutting the tank and rewelding it as explained above, would it still keep the round mortar shape as the origional and is this work worth the effort or should I just leave the diameter a few inches short and go with the tank size as it is??

[Double D]

Why bother, who's going to know, leave it as it is and get to bulding...why aren't you going to build a firing model?

[Terry C.]

I agree. Trying to open it up is going to show. It'll scream FAKE.

Leave it as-is. No one will know the difference. Better to have it slightly undersize and still perfectly round.

[Cat Whisperer]

I think the amount of work involved in slicing and welding would be a huge amount of effort that would be very difficult to get to look right.

Set it up and fill it full of bronze, bore it and press in a DOM steel tubing liner!

[GGaskill]

What are you going to fill it with?

[Powder keg]

No one will notice accept me and you. And I ain't say'n nothing.

[Cat Whisperer]

What are you going to fill it with?

17,000 lbs of scrap brass shell casings left over from the 1st gulf war.

[GGaskill]

Too bad there aren't bowling balls 13" in diameter.  About 55 lbs if same density as 16 lb bowling ball.

[entsminger]

Gee I never really thought it feasible or possible to make it capable of really shooting? Someone mentioned filling it with bronze and a heavy duty liner? Gads wouldn't that cost a fortune at around 17 thousand lbs of bronze? Wouldnt  probably cost nearly as much as Paulson Brothers $50,000 iron reproduction?
  Come to think of it though it would be cool though to make it capable of shooting ? I guess my questions then would be ....shooting what and what kind of liner or filling would it require to make it to shooting code?? Are we talking zinc 13 inchers ? Surely we aren't talking shooting real iron cannon balls or are we? If I was to try and make it to shoot, would the barrel need to be filled with something like iron or bronze or could a strong liner be reinforced with angle iron from within? I'm doing this project all alone with  no one who has a clue for this stuff around me so thanks so much everybody from sharing your opinion! It's been a great help.

  Scott
  sdakss@aol.com

[Double D]

Build your liner to be attached to a face plate that would become the front of the muzzle.  Build a long liner tube for the vent.   Build the trunnions so they go through the side of the outer tank and support the inner liner bore.

In the round end of the tank make a hole with some sort of plug. After every thing is built fill the empty space in the tank with cement.  Put in the plug.

Powder  Keg can tell you how to make a round ball mould and you can cast up some Zinc balls.

What's nice about zinc is it is hard enough to resist deformation from shooting and can be used over and and over again.

Part of the equipment the guys at Ft Shenandoah have is a shovel. They don't shoot those 24 PDR balls down range and just leave them.

[entsminger]

To go back to my origional question in this thread I have to tell you guys that I'm sort of suprised that I didn't get at least one person who thought I should try and cut the tank ( enlarge tank from 40 1/2 to 43 inches in diameter) to make it to the proper size? After all the fancy and highly technical cannon barrel  machining and making and painstaking work I"ve seen on this and other sites to make their cannon representative of the origional I would think making the barrel as accurate looking as possible would be something most of you guys would strive for even if it won't shoot? I've seen guys take many hours/days machining/welding a block of steel for a trunion or barrel end, or other complicated barrel piece so how hard could it be to just slice the tank and re-weld it to look good? With those thoughts am I still crazy for wanting to enlarge my tank to proper size?

  Scott

[Double D]

...After all the fancy and highly technical cannon barrel  machining and making and painstaking work I"ve seen on this and other sites to make their cannon representative of the origional I would think making the barrel as accurate looking as possible would be something most of you guys would strive for even if it won't shoot? I've seen guys take many hours/days machining/welding a block of steel for a trunion or barrel end, or other complicated barrel piece so how hard could it be to just slice the tank and re-weld it to look good?

  Scott

It a love of labor, probably less driven by accuracy and detail but more the pure art of creating-recreating to an infinite detail something out of a piece steel that in real form did not have the same fine detail--a work of art.  This clearly defines the beautiful cannon that George Gaskill has been working on for at least a year for example.  

With those thoughts am I still crazy for wanting to enlarge my tank to proper size?

  Scott

Yep!

[GGaskill]

Yeah, it's been almost that long.  The first post on Chaski was October 29, 2004.  But I haven't worked on it consistently, just fits and starts.

One thing the home cannon builder must be adept at is compromise.  Trunnions usually scale out to some odd dimension, like 1.27" or 1.16".  I am willing to adjust them to standard numbers (1.25" and 1.125") so I don't have to deal with special tooling.
 
With your ersatz Dictator, since you won't have a full scale one sitting nearby, your 94% model would look much better with a truly cylindrical barrel than a 100% model with a polygonal barrel.  (And you will have a polygonal barrel unless you are an infinitely better welder than I am.)  Unless you will constantly dwell on the 94% vs. 100% issue, a round one will be more satisfying.  After all, it isn't going to be 17,000 lbs of cast iron, either.

[entsminger]

I think you guys are right, I think I'm gonna just build the mortar form the tank as it is instead of cutting it up. Thanks for the input!

  Scott