Part 24 (1/2)

V' = 16182x6001/273 = 3557 litres

or at the telycerine produces 3,557 litres of per to the law of Charles, the voluas varies directly as its temperature on the absolute scale, provided the pressure rerade scale, the corresponding te 273 to the degrees centigrade]

~Pressure or Crusher Gauge~--There are o as 1792 Count Rue was, however, first used by Captain Sir Andrew noble in his researches on powder Other forms are the Rode of the English Commission on Explosives

They are all based either upon the size of an indent made upon a copper disc by a steel punch fitted to a piston, acted upon by the gases of the explosive, or upon the crushi+ng or flattening of copper or lead cylinders

[Footnote A: Invented by General Rodineers]

[Illustration: FIG 55--PRESSURE GAUGE]

Berthelot uses a cylinder of copper, as also did the English Commission, but in the simpler form of apparatus mostly used by manufacturers lead cylinders are used This for 55) consists of a base of iron to which four uprights _a_ are fixed, set round the circu rests upon the steel base let into the solid iron block A ring _c_ holds the uprights _d_ together at the top

The piston _b_, which rests upon the lead plug, is a cylinder of teth; it is turned away at the sides to lighten it as hts _d_ In the top of this cylinder is a cavity to hold the charge of explosive The weight of this piston is 12-1/4 lbs The shot _e_ is of teth, and weighs 34-1/2 lbs It is bored through its axis to receive a capped fuse

The instru of lead 1 inch long and 1 inch in diameter, and of a cylindrical forhts _a_, the piston placed upon it, the carefully weighed explosive placed in the cavity, and the shot lowered gently upon the piston A piece of fuse, with a detonator fixed at one end, is then pushed through the hole in the shot until it reaches the explosive contained in the cavity in the piston The fuse is lighted When the charge is exploded, the shot is thrown out, and the lead cylinder is s eneous structure, and should be cut from lead rods that have been drawn, and not cast separately from small masses of metal

[Illustration: FIG 56--_b_, STEEL PUNCH; _c_, LEAD CYLINDER FOR USE WITH PRESSURE GAUGE]

The strength of the explosive is proportional to the work perfor, and to get an expression for the work done it is necessary to find the nurammetres) required to produce the different a exactly si without initial velocity, and hts of the cylinders; fro ehts and the corresponding weights; the cylinders are e by57)[A]

[Footnote A: An instrument called a ”Foot-pounds Machine” has been invented by Lieut Quinan, US Army It consists of three boards, connected so as to forht (the shot of the pressure gauge) can fall freely One of the boards is graduated into feet and half feet The horizontal board at the bottom, upon which the others are nailed, rests upon a heavy post set deep in the ground, upon which is placed the piston of the gauge, which in this case serves as an anvil on which to place the lead cylinders The shot is raised by means of a pulley, fixed at the top of the structure, to any desired height, and let go by releasing the clutch that holds it The difference between the original length and the reduced length gives the coives the value in foot-pounds required to produce the different amounts of compression (Vide _Jour US Naval Inst_, 1892)]

[Illustration: FIG 57--MICROMETER CALIPERS FOR MEASURING DIAMETER OF LEAD CYLINDERS]

~The Use of Lead Cylinders~--The th of an explosive is a very simple affair, and is conducted as follows:--A solid cast lead cylinder, of any convenient size, is bored down the centre for soenerally until the bore-hole reaches to about the centre of the block The volu water into it froraduated measure, and its capacity in cubic centimetres noted The bore-hole is then erms) of the explosive pressed well down to the bottom of the hole A hole is then made in the explosive (if dynae enough to take the detonator A piece of fuse, fitted with a detonator, is then inserted into the explosive and lighted After the explosion a large pear- shaped cavity will be found to have been formed, the volume of which is then measured in the same way as before

The results thus obtained are only relative, but are of considerable value for coun-cottons) Experilycerine 14, blasting gelatine 14, and dyna 58 shows sections of lead cylinders before and after use)

[Illustration: FIG 58--LEAD CYLINDERS BEFORE AND AFTER USE]

Standard regulations for the preparation of lead cylinders may be found in the _Chem Zeit_, 1903, 27 [74], 898 They were drawn up by the Fifth International Congress of App Cheht and 200 mm in diameter In its axis is a bore-hole, 125 mm deep and 25 mm in diameter The lead used must be pure and soft, and the cylinder used in a series of tests must be cast from the same melt The tehout

Ten grms of explosive should be used and wrapped in tin-foil A detonator with a charge of 2 grms, to be fired electrically, is placed in the e is placed in the bore-hole, and gently pressed against the botto kept in central position The bore-hole is then filled with dry quartz sand, which h a sieve of 14435 mm

dia levelled off The charge thus prepared is then fired electrically The lead cylinder is then inverted, and any residues removed with a brush The number of cc of water required to fill the cavity, in excess of the original voluth of the explosive The results are only comparable if made with the same class of explosive A result is to be the mean of at least three experiments The accuracy of the method depends on (_a_) the uniform temperature of the lead cylinder (15 to 20 C 7); (_b_) on the uniformity of the quartz sand; (_c_) on the uniformity of the measurements

[Illustration: FIG 59--nobLE'S PRESSURE GAUGE]

~noble's Pressure Gauge~--The original explosive vessels used by Captain Sir A noble in his first experiments were practically exactly similar to those that he now e 59), open at both ends, which are closed by carefully fitted screw plugs, furnished with steel gas checks to prevent any escape past the screw The action of the gas checks is exactly the same as the leathers used in hydraulic presses The pressure of the gas acting on both sides of the annular space presses these sides fir, and so effectually prevents any escape In the firing plug F is a conical hole closed by a cone fitting with great exactness, which, when the vessel is prepared for firing, is covered with fine tissue paper to act as an insulator The two firing wires GG, one in the insulated cone, the other in the firing plug, are connected by a very fine platinulass tube filled with meal powder The wire becomes red-hot when connection is e which has previously been inserted into the vessel is fired The crusher plug is fitted with a crusher gauge H for deterases at the moment of explosion, and in addition there is frequently a second crusher gauge apparatus screwed into the cylinder When it is desired to allow the gases to escape for exaases then pass into the passage I, and can be led to suitable apparatus in which their volume can be measured, or in which they can be sealed for subsequent chereatest careout experiments with this apparatus; it is particularly necessary to be sure that all the joints are perfectly tight before exploding the charge Should this not be the case, the gases upon their generation will cut their way out, or completely blow out the part i the apparatus

The effect produced upon the apparatus when the gas has escaped by cutting a passage for itself is very curious The surface of the metal where the escape occurred presents the appearance of having been washed away in a state of fusion by the rush of the highly heated products

~The Pressure Gauge~--The pressure is found by the use of a little instrue which consists of a small chamber formed of steel, inside of which is a copper cylinder, and the entrance being closed by a screw gland, in which a piston, having a definite sectional area, works There is a gas check E (Fig 60) placed in the gland, and over the piston, which prevents the adas to the chamber When it is desired to find the pressure in the chaun, one or more of these crushers are made up with or inserted at the extre blown out of the gun when fired This, however, often takes place, in which case the gauges are usually found a few yards in front of the ister the pressure arefroulated to give a sectional area of either 1/12 or 1/24 square inch