On 2011-12-07, Ed Huntress wrote:
On 7 Dec 2011 02:41:23 GMT, "DoN. Nichols"
wrote:
On 2011-12-06, Ed Huntress wrote:
[ ... ]
Don, many of the old, smaller cannons were made of brass, although it
was closer to red brass (like that used in plumbing) than yellow
brass. It was used for many swivel guns, for example.
O.K. What kind of alloy would that be?
We are about to embark on a confusing journey. g When I was
Materials Editor at _American Machinist_, I made the mistake of trying
to learn all about these alloys. I remember an engineer at a copper
company looked at me when I said that, and practically laughed his
head off. 8-)
That is a bad sign, right there. :-)
First off, cannons were cast, not wrought, and cast alloys are a bit
different. Cast copper alloys' numbering begins at C8000, and there's
the one called "red brass" in the plumbing-parts field, where most of
it is used. Today, it is almost always leaded for fast and easy
machining (the lead breaks chips; it doesn't really lubricate in
copper alloys).
And 360 brass is leaded for ease of machining, and plenty of
don't run powder in this. :-)
[ ... ]
"Gun metal," as it was used for cannons, also was cast. Today's cast
gun metal, C90500, is 88% Cu, 10% Sn, 2% Zn. Another common name for
it is Tin Bronze (there are several alloys called that). I've never
heard it called red brass, but I never asked, either.
I've got a copy of _De Pirotechnia_ which includes how to sand
cast a cannon barrel -- as well as the same for a bell. (Of course,
almost everything is called by an obsolete name, making it more
difficult to understand. And the lathes for boring a cannon once it is
cast are interesting, too. :-)
Wrought alloys are much more diverse. Here you really get into trouble
with the common and commercial names. "Commercial bronze' (C22000)
contains 90% copper, 10% zinc, and no tin at all. "Red brass" in a
wrought alloy (C2300) is 85% copper, 15% zinc, no tin.
"Cartridge brass" (C26000) is 70% copper, 30% zinc.
Of course, the strength comes from the reinforcing of the
chamber, not from the cartridge case material. :-)
[ ... ]
And that's just the tip of the iceberg. A tip from an engineer I knew
who works with this stuff: forget the terms "brass" and "bronze." They
mean essentially nothing. The large majority of the "bronzes"
available today contain no tin. Some "brasses" do. (All of the above
comes from my non-ferrous bible, _Metals Handbook_, Ninth Edition.)
O.K.
And if you're going to make a small cannon out of bar stock, stick
with steel. Then you won't have to worry about Charpy impact strength,
or stress-corrosion cracking, or any of the rest of the black magic
associated with highly-stressed copper alloys.
Amen! (Not that I plan to do this -- but whoever the OP was
apparently did intend to do so.
[ ... ]
And is there any practical way for the home machinist to tell
what alloy they have? (Other than buying a certified alloy from a good
vendor.)
[ ... ]
Not that I've ever heard of.
I was afraid of that.
Thanks for all the typing and information,
DoN.
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