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.
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.