pict http://groups.yahoo.com/group/SCA-Gunners/photos/album/564888360/pic/992084227/view?picmode=&mode=tn&order=ordinal&start=1&count=20&dir=ascAccidental discharge, blamed on a stray ember? I thought that would not happen if the charge had been properly made. I devised an experiment.
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My controled test was run last monday, in which I tried to determine how long
it would take to ignite a black powder charge with a red-hot charcoal brickette,
if protected by a charge casing constructed of exactly 2 layers of heavy duty
kitchen foil.
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I posted pictures in the SCA gunners list...3 pictures are in photos/kismet. One showing the setup - the shape of the
charges which were constructed, and the container, an alum. coke can
bottom 1/3.
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I wanted a metal container to keep the charge seated on the coal and the
heat concentrated as it might in a gun tube. On the other hand I did not want to
contain gases which might cause an explosion so the can was kept short.
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The charge bottom is exactly 2-layers of heavy duty foil, using my
cannon's(kismet's) charge shaper/mold(shaper pressed down into the center of a
sheet, so that the bottom would not have any folds), and a half ounce of 1F
black powder (this was about 1/3 inch thick powder layer), goex, fresh can.
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The second picture shows how the charge fits inside the container: about
90% close fit.
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I removed 2 charcol bricketts from the middle of a grill, which were by my
best judgement at peak heat. They had been heating about a half hour, and were
fully covered in ash and glowed a fairly uniform dull red. these were removed by
thongs and placed in the 2 test containers. and within 20 seconds I put the
first charge on and 5 seconds later the second charge.
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I noted the time and stood clear. The 3rd picture showes the test in
progress. After 15 minutes passed and neither charge had ignited, I terminated
the formal test, concluding that the coals had cooled and there was little
prospect of ignition. Nevertheless, for safety reasons I did not approach the
test setup until approximatly 40 minutes passed, at which time I lightly hosed
down the setup from a distance. 20 minutes later I approached the setup and poured
enough water to fill the container, and found (somewhat to my alarm) that the
coals were still hot enough to boil the water I added and that the powder charge
was still being heated.
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only 2 tests, but I feel confident In concluding that 2 layers of foil well protect a charge from
accidental ignition from coals. In reality, an ember in a cannon would not
be nearly as large, hot and long burning as a charcol brick, and anyway it would
only need to protect the charge from igniting for a minute or so, to allow
completion of the loading process.
Rather than repeating this test, I might try a single layer of foil, and I hypothesize that would protect from discharge for a minute.
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A properly made foil-wrapped charge with not 2 but at least 3-4 layers of
foil seems essentially proof of any risk of accidental discharge by an ember. I
don't know what caused the accident, but it was not 'only' a stray ember.
> > > -Rick Orli
