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AMIDE
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AMIDE 17- 16-!1 , , 15- : See also:steam-See also:engine, representing graphically by a See also:curve CPD the relation between the See also:volume and pressure of the See also:powder-See also:gas; and in addition the curves AQE of See also:energy e, AvV of velocity v, and MT of See also:time t can be plotted or derived, the velocity and energy at the muzzle B being denoted by V and E. After a certain See also:discount for See also:friction and the recoil of the See also:gun, the See also:net See also:work realized by the powder-gas as the shot advances AM is represented by the See also:area ACPM, and this is equated to the kinetic energy e of the shot, in See also:foot-tons, (I) e=224- (1-I d22tan2S) 2a, in which the See also:factor 4(k2/d2)tan2S represents the fraction due to the rotation of the shot, of See also:diameter d and axial See also:radius of gyration k, and S represents the See also:angle of the rifling; this factor may be ignored in the subsequent calculations as small, less than 1 %. The mean effective pressure (M.E.P.) in tons per sq. in. is represented in fig. 3 by the height AH, such that the rectangle AHKB is equal to the area APDB; and the M.E.P. multiplied by ;,rd2, the See also:cross-See also:section of the See also:bore in square inches, gives in tons the mean effective thrust of the powder on the See also:base of the shot; and multi-plied again by 1, the length in inches of the travel AB of the shot up the bore, gives the work realized in See also:inch-tons; which work is thus equal to the M.E.P. multiplied by ird2l=B—C, the volume in cubic inches of the rifled See also:part AB of the bore, the difference between B the See also:total volume of the bore and C the volume of the powder-chamber. Equating the muzzle-energy and the work in foot-tons w V2 B --C (2) E=2240. 2g — I2 XM.E.P. V2 w (3) M.E.P. = 2240 2g B?2C. Working this out for the 6-in. gun of the range table, taking L=216 in., we find B—C=61oo cub. in., and the M.E.P. is about 6.4 tons per sq. in. But the maximum pressure may exceed the mean in the ratio 012 or 3 to I, as shown in fig. 4, representing graphically the result of See also:Sir See also:Andrew See also:Noble's experiments with a 6-in. gun, capable of being lengthened to 100 calibres or 50 ft. (Proc. R.S., See also:June 1894).
On the See also:assumption of See also:uniform pressure up the bore, practically realizable in a Zalinski pneumatic See also:dynamite gun, the pressure-curve would be the straight See also:line HK of fig. 3 parallel to AM; the energy-curve AQE would be another straight line through A; the velocity-curve AvV, of which the See also:ordinate v is as the square See also:root of the energy, would be a See also:parabola; and the See also:acceleration of the shot being See also:constant, the time-curve MT will also be a similar parabola.
If the pressure falls off uniformly, so that the pressure-curve is a straight line PDF sloping downwards and cutting AM in F, then the energy-curve will be a parabola curving downwards, and the velocity-curve can be represented by an See also:ellipse, or circle with centre F and radius FA; while the time-curve will be a sinusoid.
300
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200
1500
100
0.4 See also:CORDITE
3000
- CORDITE r-r_ 2800
03~ -_ORDITE _~;36 CORDITE ~ . _. _ • —_
c . 2800
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~ _. --- 2400
4 -CORDITE 2200
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Plugs 7 B 0 10 11 12 3 14 h See also:Rifle
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8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 Velocity Curves, from Chronoscope experiments in 6 inch gun of soo calibres, with Cordite.
employed the See also:steel See also:spheres of See also:bicycle See also:ball-See also:bearings as safety-valves, loaded to See also:register the pressure at which the powder-gas will See also:blow off, and thereby check the indications of the crusher-See also:gauge (Proc. R.S., See also: See also:Chevalier d'Arcy, 176o. also experimented on the pressure of powder and the velocity of the See also:bullet in a See also:musket See also:barrel; this he accomplished by shortening the barrel successively, and measuring the velocity obtained by the ballistic pendulum; thus See also:reversing Noble's See also:procedure of gradually lengthening the gun. But the most See also:modern results employed with See also:gunpowder are based on the experiments of Noble and See also:Abel (Phil. Trans., 1875—1880—1892—1894 and following years). A See also:charge of powder, or other explosive, of varying See also:weight P Ib, is fired in an See also:explosion-chamber (fig. 7, See also:scale about g) of which the 0234 e 2 4 Travel in feet. But if the pressure-curve is a straight line F'CP sloping upwards, cutting AM behind A in F', the energy-curve will be a parabola curving upwards, and the velocity-curve a See also:hyperbola with center at F'. These theorems may prove useful in preliminary calculations where the pressure-curve is nearly straight; but, in the See also:absence of any observable See also:law, the area of the pressure-curve must be read off by a planimeter, or calculated by See also:Simpson's See also:rule, as an See also:indicator See also:diagram. To measure the pressure experimentally in the bore of a gun, the crusher-gauge is used as shown in fig. 6, nearly full See also:size; it records the maximum pressure by the See also:compression of a See also:copper See also:cylinder in its interior; it may be placed in the powder-chamber, or fastened in the base of the shot. In Sir Andrew Noble's researches a number of plugs were inserted in the See also:side of the experimental gun, reaching to the bore and carrying crusher-gauges, and also chronographic appliances which registered the passage of the shot in the same manner as the electric screens in Bashforth's experiments; thence the velocity and energy of the shot was inferred, to serve as an See also:independent See also:control of the crusher-gauge records (See also:figs. 4 and 5). As a preliminary step to the determination of the pressure in the bore of a gun, it is desirable to measure the pressure obtained by exploding a charge of powder in a closed See also:vessel, varying the weight of the charge and thereby the See also:density of the powder-gas. The earliest experiments of this nature are due to See also:Benjamin See also:Robins in 1743 and See also:Count See also:Rumford in 1792; and their method volume C, cub. in., is known accurately, and the pressure ', tons per has been revived by Dr Kellner, See also:War See also:Department chemist, who ~ sq. in., was recorded by a crusher-gauge (fig. 6). 278 The result is plotted in figs. Additional information and CommentsThere are no comments yet for this article.
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