On Mon, 05 Dec 2011 21:03:39 -0500, Ed Huntress
wrote:

On 6 Dec 2011 01:29:02 GMT, "DoN. Nichols"
wrote:

On 2011-12-05, wrote:
On 4 Dec 2011 06:16:47 GMT, "DoN. Nichols"
wrote:

[...]

I personally would never consider putting black powder in
anything made of brass. Stick with bronze -- it is much stronger and
safer.


http://www.youtube.com/watch?v=IxHW-QGMuZ4

:-)

Good thick walls for the bore.

But what was being used as powder in it? The color did not
look like either black powder or smokeless, so what was it? That would
determine the peak pressure and thus the proper metal.

Enjoy,
DoN.

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.

One of my alloy books says that there wre over 300 named alloys called
"brass" or "bronze" in the 1930s. g But you're basically right --
tin bronze, also called "gun metal," is stronger than yellow brass,
and has somewhat greater impact strength.

More than tensile strength, you need ductility and impact strength.
Hell, the guns on the Monitor were made of cast iron, as were most
guns of the time, with wrought-iron hoops on the breech to prevent
castastrophic explosions. Even so, the gunnery officer would only load
them to around 50% of their designed powder load. A big gun in that
turret must have made them nervous.

Still, after 1,000 - 2,000 or so shots, some of those Civil War-era
cannons would let go. It was a hazard of war.

Bronze is pretty sensitive to small variations in compositioin, in
terms of elongation (ductility) and impact strength. I have the
complete contemporary listings for compositions and properties, but I
think you can find that stuff online these days.

Gun metal is what you want. It's around 10% - 12% tin, IIRC, with most
of the rest copper. I'll look up the full composition if anyone is
interested.

BTW, the "Gunmetal" listing in Wikipedia is screwed up. Don't rely on
it. They say it's also called "yellow brass" in the US (it isn't), and
then their reference, a UK web page, says it's called "red brass" in
the US (it isn't).

Sheesh. I've never contributed to a Wikipedia listing, but this one
needs some corrections.

--
Ed Huntress