On 2011-12-22 07:32:04 -0800, David Dyer-Bennet said:

William Hamblen writes:

On 2011-12-21, David Dyer-Bennet wrote:

I managed this one of a civil war cannon firing just by finger timing,
though.
http://dd-b.net/cgi-bin/picpage.pl/dd-b/SnapshotAlbum/data/2004/05010-Freedom-Day?pic=ddb%2020040501%20010-011.

I'm

actually in front of that last gun -- but well to the side. I was
reasonably sure they weren't going to turn it quickly enough to catch
me. I'm not sure why *they* were happy with the setup, though. Then
again, doing that kind of demo in a public space (that's actually on the
state capitol lawn) it's hard to keep a clean firing line.

Here's my version of a cannon flash (my apologies if this doesn't work):
http://www.flickr.com/photos/65942246@N03/6551282185/.

Very nice! I particularly love the jet from the touch-hole. I believe
gunners in the Royal Navy were trained to stop their touch-holes to
limit erosion by the gas gets (which must get exciting, given that
they're using carriages that move a couple of feet in recoil).

I believe you will find that is not related to old match fired guns.
Up until the mid 18th century British naval guns (and the majority of
field guns) were fired with the use of a linstock, a staff with a slow
match attached to the end. This device gave the gunner a stand off
distance of about 6 to 7 feet. This was necessary because the jet from
the touch-hole was unpredictable, and it gave them the reach to be
outside the track of the recoiling gun carriage.

By the early 18th century the touch-hole and quill fuse was replaced on
the naval gun with a flintlock firing device which was triggered by the
gunner pulling on a lanyard, usually 6 to 8 feet long. Field guns
continued to be fired with a mix of the old touch-hole quill fuse
method and the flintlock device into the early 19th century until the
introduction of the friction fuse, or friction tube igniter which was
also triggered with a lanyard.

Here is where the vent sealing story comes along. With muzzle loaded
field and naval guns, on firing friction igniter fuses, the used tube
is blown out of the vent by the explosive pressure. You would have seen
this with the Civil War era guns you are familiar with. No gunner is
going to manually try to contain that. It would be like trying to
restrain a bullet by putting your hand over the end of the barrel.

With the introduction of early breech loading naval guns in the late
18th, and early 19th century, which were still fired in the traditional
manner, the erosion from the touch-hole was found to interfere with the
breech mechanism. So the Royal Navy developed a special "vent sealing
friction igniter tube for these guns. it was "T" shaped and was locked
into the touch-hole with a bayonet fitting. When the gun was fired a
ball sealed the vent by being forced into a conical section of the
igniter tube. The seal was removed when the breech was opened for
reloading.


The lanyard lives on today with many examples of modern field
artillery, where the lanyard allows the gunner to be a safe distance
from the recoiling gun. That said modern naval guns are fired
electrically as are quite a few modern field guns.



My brother was on the Federal battery on the other side of the field,
but they wouldn't let spectators up there and I couldn't get a shot
of him.

Simulating firearms combat gets really complicated; I'm glad I'm not the
one having to invent (and test) how to do it reasonably safely.


--
Regards,

Savageduck