Question about Mortar Shape

[Dross Drunk]

 Hello again all !

 I have a friend, that after seeing my thundermug, wanted one for his very own, and he works at a place that has large quantities of square stock of some pretty strong tool steel.

 He is wondering if it would be possible to create a thundermug, and leave the outside square .with only slight radiusing to the edges,and then make his bore round, I wanted to tell him that if it hasnt been tried and true for over a century, then it probably wouldnt be wise, but I really didn't have an argument that would address the outside shape other than never seeing one before,and that there was probably a reason for that, I mentioned that I was aware of the hex or octagon type barrels of black powder rifles, but I had never seen a square one.

 So could someone please chime in here and maybe give me some information about this idea,...it just doesn't sound right to me, but I am very new at this and havent the experience to know what to tell him....
            thanks for any input.......................and have a safe and happy upcomming 4th

[Double D]

Square shape is fine.  It's the tool steel thing that concerns me.  Tool steels often run to brittle if not annealled properly.

[Cat Whisperer]

Base your calculations for wall thickness at the thinnest point.

Tool steels are OK, ensure that you get one that has good maleability (look at charpy notch test values, not just strengths).  It is the repetitive hammering and resistance to cracking that are important).

"simple, plain" 1018 and similar fit the characterists needed for cannons very well.  Using a 'numbered' steel tells you much about the quality of the steel (compared to an unknown 'mystery steel').

The design of the interior of the bore - finish and interior corners is important to reduce stress risers - is important as well.

Although unusual, the square barrel has some interesting advangages in assembling to other things.

Finding  a pre-1899 design might be a bit of a challenge though.  (Expect to offend traditionalists.)

[seacoastartillery]

     I'm offended!  I'm offended!  Only kidding.  Tim,  I'm afraid I am going to agree with Double D on this one.  Very few people have the resources available to test the hardness of their 'Tool Steel'.  However, if by Tool Steel, he really means 'Alloy Steel' like 4130, 4140, 4142, 4150, etc., etc., then that's a different story.  I wouldn't trust ANY tool steel to be of the correct hardness on the Rockwell 'C' Scale to be safe for cannon construction.  Hardness testers with diamond penetrators which are what you need for steel hardness testing are not commonly available in machine shops , because they are rarely used and are very expensive to have sitting around gathering dust, about 8 to 15 thousand dollars.
     Square, why not?

Regards,

Mike and Tracy

[Cat Whisperer]

M&T -

Not to be shocked.  My 'assumptions' were based on 'large quantities' and that one doesn't USUALLY start machining tool steels (of this size) that are in the hardened condition.  Pre-hardened is often found and being tool or alloy steel, one USUALLY has good information about both the kind of steel it is and the condition (hardness/temper).

As you know there are AT LEAST two major alloys of tool steel, with MANY variations.  But with the proper choice (and temper) the 'tool steel' may be a better choice than a 'non tool-steel'.

As a side, tool steel is a term often referring to it's ability to maintain sharpness of edge under difficult conditions - which implies toughness and improved ability to conduct away heat, is it not?  So the crystaline structure of body-centered vs. face/edge centered provides the extra density that helps.  (You're testing my memory here.  The interstatial molecules are inside the normal cubic structure of the ferric molecules hence take up less volume.)

So there is the obvious issue, well discussed thus far, of hardness vs. brittleness; hence the need to be fully aware of what one is doing. 

[KABAR2]

Why not make the bore square?  heck we see early 17th century round tube cannon with square bores, there are examples in one of the Rssian museums,  it would mess with peoples minds a bit also.................... who knows maybe he could start a new trend.....
we already have tennis ball and golf ball mortars......... now we could have a "BRICK" mortar.....


Allen <><

[dan610324]

why use bricks ??  when we have houndreds of billions old cd discs all over the world     soon will the dvd also be antique 
it would be nice to see the first cd cannon here