Among the numerous apparatus that have been devised for determining the
power of powder, those designed for military purposes are the ones most
extensively used. Up to the present, very few experimental apparatus
have been constructed for civil uses, although such are no less
necessary than the others. Mr. D'O. Guttman has examined the principal
types of dynamometers with respect to their use for testing explosive
materials, and, after ascertaining wherein they are defective, has
devised an apparatus in which the principle is the same as that employed
by Messrs. Montluisant and Reffye at Meudon, that is to say, one in
which the force of the powder is made to act upon a lead cylinder fixed
in a conical channel. Mr. Desortiaux objects that in this system, when
it is employed with charges for cannons, the action has already begun
when only a portion of the powder is burned. To this, Mr. Guttman
responds that his apparatus operates only with small charges (300
grains), which practically inflame simultaneously in every part when the
igniting is done in a closed space. In order that the force may not be
made to act in one direction only, the inventor uses two leaden
cylinders. His apparatus is shown in the accompanying Figs. 1, 2, and 3.
It consists of a median piece, a, and of two heads, b, of an external
diameter of four inches. These pieces are of tempered Bessemer steel.
The two heads are four inches in length, one inch of which is provided
with a screw thread. Each of them contains an aperture, c, 1.34 inches
wide below, 1.3 inches wide above, and 1.18 inches deep. This aperture
is followed by another and conical one, d, 1.38 inches deep, and 0.4
inch wide at its narrowest end, and finally by another one, e, 0.4 inch
wide, which runs to the exterior. The median piece, a, is 4 inches long.
It is provided at the two sides with nuts, between which there is a
cylindrical space, f, 1.8 inches long, designed to receive the charge.
The inflaming plug, g, is screwed into the exact center of the median
piece, a, which it enters to a depth of one inch. Into the space that
still remains free is screwed a plug, h. The lower surface of the plug,
g, contains a hollow space, 0.6 inch wide and deep. This hollow is
prolonged by another one, 0.24 inch wide, and contains a valve, i, which
has a play of about 0.08 inch. The three parts are connected by a key
which passes into the holes, x, and are rendered tight by copper rings,
y.
When it is desired to charge the apparatus, a leaden cylinder, 1.34
inches long and 1.3 inches in diameter, is placed in one of the heads,
and the median piece is so screwed that it can be made still tighter by
a few turns. Then a steel plate, k, 1.3 inches wide by 0.2 inch thick,
is placed against the cylinder, and against this plate again is placed a
cardboard disk, 1.34 inches wide by 0.4 inch thick. This completely
closes the hollow space. The steel plates and heads are marked with the
figures 1 and 2, which, through the pressure, are impressed upon the
leaden cylinders. Then the charge of powder, weighing exactly 300
grains, is introduced, and a new cardboard disk, a steel plate, and a
leaden cylinder are inserted, and the second head is screwed up. The
apparatus is now ready to operate. An ordinary priming is placed on the
pyramid, h, and the plug with the valve is screwed down in such a way
that the latter shall have a little play. By means of a hammer, m, a
smart blow is given the valve i, and this detonates the priming, and
causes an explosion of the charge. The gases make their exit through the
pyramid, h, and lift the valve and press it against the plug, so that
their escape is effectually prevented. In fact, the explosion takes
place without noise. A slight whistling, only, indicates that the
capsule has not missed fire, and that the apparatus may be immediately
opened, the gases having condensed in the interior. It is well, however,
to place the closed apparatus in water, in order that the residua that
have entered the threads of the screw may become detached, and that the
apparatus may be opened easily. Although there is no danger in standing
alongside the apparatus, it is much better to spring the hammer by means
of a cord of a certain length, since the valve and especially the
pyramid gradually burn and may be thrown out. With some kinds of powder
the pyramid rapidly melts, and must be frequently replaced.
[Illustration: APPARATUS FOR MEASURING THE FORCE OF EXPLOSIVES.]
The two cones of lead obtained are then measured to 0.004 of an inch by
means of a gauge (Fig. 3).
The inventor has made numerous experiments with his apparatus, and
thinks it permits of determining the total force developed by powder
very perfectly.
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