MODERN BIG GUNS.

Taranaki Daily News, 24 September 1915, Page 3

MODERN BIG GUNS.

LECTURE BY PROFESSOR R. J. SCOTT. i . ■ A VISIT TO THE WORLD'S WORKSHOPS. "Guns and (Projectiles, their Design and Construction," was the title of the lecture delivered by Professor R. J. Scott to the Canterbury College Engineering Society last week.

The design and construction of guns and projectiles, Professor Scott said in opening, formed a most important branch of mechanical engineering, and called for great skill. The gun was a heat engine of the type of the internal combustion engine, and its efficiency might be compared with that of the gas engine. Of the heat energy of a modern gun 20 per cent, was converted into work, 2 per cent, was lost owing to a displacement of the atmosphere at the muzzle, and 78 per cent, was rejected at the muzzle. But the mechanical efficiency of the gun was high, being about 90 per cent. In the case of the modern gas engine the mechanical efficiency was only 84 per cent., but the absolute heat efficiency was 30 per cent., so that the modern gas engine was the more effective machine.

Indicator diagrams were shown of, the pressure in the old castriron gun, which the lecturer remarked used to come to pieces sometimes, to put it mildly. In those the pressure soared to 25 tons to the square inch, but produced only a muzzle velocity of 1600 ft per second, while the latest 6in guns, with a maximum pressure of 20 tons, imparted a velocity of 3000 ft per second to the 1251b projectile.

This led the lecturer to speak of the complicated ring stresses set up in the latest guns, and the necessity for -making them in four or more rings, thus applying external pressure to each ring. After running through the early experiments with big guns, and the winding of wire upon them, the lecturere showed a picture of the biggest steam hammer in the world, a 100-ton engine, at Krupps, but excused himself for showing this by remarking that Krupps had had to go to Belgium for it. Later he showed a big hydraulic press at Krupps, made in England. From this stage some remarkably good slides from photographs at Vickers' and Beardmore's were shown, to illustrate the manufacture of a 13.Sin gun. The 96-ton ingot from which the jacket was made, the lecturer said, had to be cut at both ends after forging, and one set of cutters took eight hours to go through a sft ingot. After that the solid ingot had to be bored out to a 30in hole 18ft long, and the process was forty hours' work. During that time 200 gallons of. soap and water per minute were squirted into the bore, at a pressure of 401b or 501b, to lubricate the tool. In the slow processes of forging, annealing, turning and boring, the lecturer demonstrated the reason why big guns could not be turned out quickly, The best gun in the British Navy, Professor Scott said, was the 12in fifty calibre gun, with a muzzle velocity of 3000 ft and a muzzle energy of about 54,000 tons. He had often* been asked what was the extreme range of a gun, but that was dependable not only on the gun, but also on tho way it was mounted. It had long been the practice in the British Navy and m6*st other navies to provide an elevation of 15 degrees and a depression of 7'/;. degrees. That gave a range of, roughly speaking, 19,000 yards for the 12in gun. It had been contended that the atmospheric conditions at sea would not permit of an engagement at a longer distance than ten or eleven miles, although the best British gun had a range of, probably, twenty-five to twenty-eight miles, at an elevation of 45 degrees. One of the surprises of the war had been the fact that m all the engagements the British guns had been outranged by the German, but this was readily explained when he stated that the maximum elevation in the German service was 30deg. At an elevation of 15 degrees the British 12in gun had a range of 19,000 yards, while at an elevation of 30 degrees the German B.2in gun had a range.of 22,000 vards, the llin gun a range of 25,000 yards, and the 12in gun a range of 27,000 yards. AH that was entirely due to the manner of mounting. Professor Scott remarked that when a projectile was fired from a gild at a certain angle it kept the same angle in Its flight, and did not turn oonveniently, with its nose first. That might or might not be a disadvantage. If the projectile came down on the deck on its side there was quite sufficient energy to crash through into the vitals of the ship,

In conclusion, Professor Scott dealt interestingly with shrapnel and armorpiercing projectiles. U e showed a process in which it took five lathes and one grinder to turn out eighteen shells In a day, and remarked significantly that one gun could dispose of them in one minute.