On the back there was no bulge, nor any cracks or other defects of any kind on face or back. Shot 2.-15 cm, steel shell L/3.2; weight 45.7 kg. The projectile was shattered into fragments, of which 28, weighing 27.5 kg. were collected. The point of the projectile remained sticking in the plate, but fell out at the next shot, upon which the depth of penetration became measurable and was found to be 135 mm. Around the point of impact no edgings and no peeling off of the material visible. Neither cracks nor other defects visible on face or back. On the back no bulge. Shot 3.-15 cm. steel shell L/3.2; weight 45.5 kg. The projectile was shattered into fragments, of which 24, weighing in all 24 kg., were collected. The point of the projectile remained sticking in the plate; the depth of penetration became measurable at the next shot and was found to be 110 mm. Around the shothole on the face no edgings appeared, but the material flaked off as far as shothole 2. From shothole 2 a horizontal and a vertical through crack extended to the right and bottom edges, respectively. On the back no bulge was noticeable, The plate remained in its original position, and the wooden backing was not injured. In this third shot it happened that, on account of the darkness, instead of having a distance of 4 calibers = 600 mm. mean distance between shotholes 2 and 3, unfortunately this mean distance was accidentally reduced to but 290 mm. This alone will explain the cracking of the plate, which would undoubtedly have resisted the attack, as may be concluded with certainty from the conduct of the plate at shot 4. After the 3d shot, which was already fired with the maximum charge of the powder on hand, no further increase of charge-with corresponding increase of velocity-was possible; consequently, shot 4 had to be fired with the same charge as shot 3. Shot 4.-15 cm. steel shell L/3.2; weight 45.55 kg. The projectile was shattered into fragments, of which 51, weighing 22 kg., were collected. Around the shothole there was neither edging nor peeling off visible. The depth of penetration of the projectile was 135 mm. A through crack, extending from shothole 2 through shothole 3 to shothole 4 resulted, and also another, not connected wilh the first, to the left-hand edge of the plate; besides, a hair crack running towards the upper edge of the plate made its appearance. From the slight depth of penetration of 110 and 135 mm., in The projectile was shattered into fragments, of which 49, weighing 30.5 kg. in all, were collected. The plate received an indentation 92 mm. deep; over an area 270 x 285 mm. around the point of impact, on the face of the plate, the hard layer peeled off to a depth of 10 mm. The back of the plate remained unaltered and showed neither bulge nor crack. Shot 2.-15 cm. steel shell L/3.2; weight 45.7 kg. Velocity of impact Energy, total. . . Energy per cm. of circumference 20.342 mt. Energy per cm.2 of cross-section 5.461 mt. The projectile was shattered into fragments, of which 41, weighing 21.5 kg. in all, were collected. The head of the projectile remained sticking in the plate and fell out at the third shot; the depth of penetration could then be measured and was found to be 100 mm. The material over an area 220 x 190 mm. peeled off to a depth of 10 mm. On the back appeared a bulge 46 mm. high, free from cracks. The plate showed neither crack nor flaw on face or back; the backing remained unimpaired. Shot 3.-15 cm. steel shell, L/3.2; weight 45.5 kg. Velocity of impact Energy, total Energy per cm. of circumference. Energy per cm,2 of cross-section. 673.15 m. 1050.83 mt. 22.448 mt. 6.026 mt. The projectile was shattered into fragments, of which 48, weighing 18 kg., were collected. The point of the projectile remained sticking in the hole made by the shot, its measureable penetration 52 mm.; the border of the point of impact over an area 280 x 260 peeled off as in previous cases. On the back of the plate appeared a bulge 41 mm. high, free from cracks; the plate shows no other defects whatever, either on its face or back. PLATE 6559. The un-Harveyed homogeneous nickel-steel plate, prepared according to a process peculiar to the works, had the dimensions 1720 x 1720 x 220 mm. Shot 1.-15 cm. steel shell L/3.2; weight 45.5 kg. The projectile was shattered into fragments, of which 25, weighing 32.5 kg. were collected. The point of the projectile remained sticking in the plate but fell out at the second shot, leaving the depth of penetration measureable at 125 mm. Around the point of impact, over an area of 240 x 270 mm, the material was pressed away, without causing any portion of the face of the plate to peel off. On the back there was no bulge, nor any cracks or other defects of any kind on face or back. Shot 2.-15 cm, steel shell L/3.2; weight 45.7 kg. The projectile was shattered into fragments, of which 28, weighing 27.5 kg. were collected. The point of the projectile remained sticking in the plate, but fell out at the next shot, upon which the depth of penetration became measurable and was found to be 135 mm. Around the point of impact no edgings and no peeling off of the material visible. Neither cracks nor other defects visible on face or back. On the back no bulge. Shot 3.-15 cm, steel shell L/3.2; weight 45.5 kg. The projectile was shattered into fragments, of which 24, weighing in all 24 kg., were collected. The point of the projectile remained sticking in the plate; the depth of penetration became measurable at the next shot and was found to be 110 mm. Around the shothole on the face no edgings appeared, but the material flaked off as far as shothole 2. From shothole 2 a horizontal and a vertical through crack extended to the right and bottom edges, respectively. On the back no bulge was noticeable, The plate remained in its original position, and the wooden backing was not injured. In this third shot it happened that, on account of the darkness, instead of having a distance of 4 calibers 600 mm. mean distance between shotholes 2 and 3, unfortunately this mean distance was accidentally reduced to but 290 mm. This alone will explain the cracking of the plate, which would undoubtedly have resisted the attack, as may be concluded with certainty from the conduct of the plate at shot 4. After the 3d shot, which was already fired with the maximum charge of the powder on hand, no further increase of charge-with corresponding increase of velocity-was possible; consequently, shot 4 had to be fired with the same charge as shot 3. Shot 4.-15 cm. steel shell L/3.2; weight 45.55 kg. The projectile was shattered into fragments, of which 51, weighing 22 kg., were collected. Around the shothole there was neither edging nor peeling off visible. The depth of penetration of the projectile was 135 mm. A through crack, extending from shothole 2 through shothole 3 to shothole 4 resulted, and also another, not connected with the first, to the left-hand edge of the plate; besides, a hair crack running towards the upper edge of the plate made its appearance. From the slight depth of penetration of 110 and 135 mm., in shots 3 and 4, respectively, we may conclude that this plate would have easily resisted 15 cm. steel shells with impact velocities of 690 and 700 m. Although the plate showed several cracks after the last two shots, it still held together, and the backing remained uninjured. The result of the trial may be summed up to the effect that both plates, in spite of the reduced thickness (by 50 mm.), showed themselves far superior to the Witkowitz standard plate previously tested in Pola, and which was victorious over the products of all the different German and English armor-plate works. Both plates showed that they possessed considerably more resisting power than was required to fulfill the conditions fixed for the three coast-defense vessels by the Navy Department of the Imperial War Ministry. The Witkowitz works guaranteed that the trial plates, tested under the conditions in force at Pola in November, 1893, would show such a behavior that no opening at the back of the plates would take place. Comparing the two plates one with the other we are struck with the fact that the special plate, although Harveyized on the surface, was bulged out on the back, but still without in the least opening up, while the homogeneous plate showed no change whatever on the back. In the following table the attempt is made to make a comparison between the tests above given and the recently officially published Krupp and American trials. There is considerable difficulty in this attempt because in the trials to be compared the thickness of plates as well as the weights and velocities of the projectiles were different. The formula which served as a basis for the comparison is that of De Marre, which expresses the velocity of the projectile as a function of the quality number for steel plates (1530), the diameter of the projectile, the thickness of the plate and the weight of the projectile: in which, v = velocity, d = diameter of projectile, p= weight of projectile, b= thickness of plate. In the case before us the quality is to be regarded as the variable, from which the following table results: From this table it appears that in quality the plates tested in Witkowitz proved far superior to the Iowa plate, and that, according to the official record, they are equal to the 146 mm. Krupp plate. ww It should be noticed that the 220 mm. Witkowitz plates were not bolted, and had a weaker backing with thinner inner skins than the 146 mm. Krupp plate. By calculation the thickness of a steel plate to resist a 15-cm. projectile with 677.3 m. velocity should be 309 mm., corresponding to a wrought-iron plate of equal resistance 443.5 mm. thick. According to English authorities Harvey plates of the best quality surpass wrought-iron plates of equal thickness by 83%. The Witkowitz plates will surpass them by 101.6%. -Mittheilungen aus dem Gebiete des Seewesens, No. II, 1897. Trial of Side and Deck Armor for the United States Battleships Kearsarge and Kentucky. A test plate was recently fired at with a ten-inch gun at the Naval Proving Ground, Indian Head. The plate was one of a set of face hardened, reforged nickel steel plates, which is being furnished by the Carnegie Steel Company for the side armor of the Kearsarge. It measured 7%1⁄2 feet in height and 16 feet in width and tapered from a thickness of 161⁄2 inches to 91⁄2 inches. The plate was set up with the thick edge of the plate down and the outer surface vertical, the center of the plate being normal with the line of fire. It was backed with 12 inches of oak and 1⁄2-inch skin plates. The plate was secured to the structure by six holding-in bolts, and the distance between gun and plate was 334 feet. In the first round a Carpenter shot weighing 500 pounds was fired from a 10-inch breech loading rifle. The striking velocity was 1,293 feet a second and the striking energy 5,802 foot-tons. The projectile struck the plate and smashed to pieces, the head of the shot remaining in the plate. Fifty-nine fragments in all, weighing 78 pounds, were picked up in front of the plate. The effect upon the plate was slight and very local. The backing was uninjured and there was no apparent effect on the skin plates. The estimated penetration was four inches. The diameter of the splash was 10 inches and of the flaking 14 inches. The plate where it was flaked seemed to be of very fine quality. The plate was then attacked with a 10-inch Wheeler-Sterling armor-piercing projectile, weighing 500 pounds, which was of extreme hardness from the point to 11⁄2 inches in rear of the bourrelet. The striking velocity was 1850 feet a second and the striking energy 11,877 foot tons. The projectile smashed on the plate, the head remaining embedded. The projectile broke up much less than that of the first round, 32 pieces being found in front of the plate, their total weight being 353 pounds, and the largest piece weighed 531⁄2 pounds. The estimated penetration was 9 inches. The plate was dished at the edges of the flaking to about 4 inch below the general surface. The backing was uninjured and the skin plates were slightly bulged out at the top edge, where the bolts were carried away in the previous round. The second armor bolt from the right edge in the center row was carried away, and the lead washers of the third and fourth bolts of the same row were sheared off. The excellent behavior of this plate resulted in the acceptance of the group of armor which it represented. We have also received interesting particulars of the ballistic test of two protective deck plates, 134 inches in thickness, manufactured by the same Journal 12. |