Science Siftings

New Zealand Tablet, 11 May 1916, Page 43

Science Siftings

By ‘Volt.’

Marvels of Ship-Construction.

Each man-of-war is built upon paper before a single plate of steel is forged. Not only are length and breadth .of a ship decided upon, but the naval constructor can tell to an ounce how much water she will displace when her armor and guns are mounted upon her, how many times her propellers will revolve in a minute with a given pressure of steam, and how many tons of coal an hour must be consumed to attain a certain rate of speed.

Airships are .Expensive. Airships are an enormous item of expense in the accounts of an army. Zeppelins, for example, cost £IOO,000 to build. Their construction takes a year, yet they can be totally wrecked by a high wind in half an hour. To fill a Zeppelin with gas costs £6OO every time a full head of hydrogen is pumped into the 500 ft envelope of the airship. The great motors of the vessel drink up petrol at the rate of thirty gallons an hour. Moreover, these delicate machines require a £22,000 shed to house them if they are to be safely anchored away from the presence of boisterous weather.

Any Old Bones.

Bones are not wasted. The chief product is glue, and among other materials which are obtained from them are soap, glycerine, and fertilizers. After being carefully separated by workmen they are soaked in a weak solution of sulphuric acid. From the soaking tanks the bones emerge white and perfectly clean. They are then placed in steam tanks, where, after being subjected to a pressure of steam for several hours, a trap-door is opened at the bottom of the digester, as it is called, and the liquid glue that has been extracted is drawn off. The liquid glue is partly evaporated and a portion is allowed to harden for commercial use as glue, and a part is refined and sold for gelatine for table use. Floating on the top of the glue in the digester is a quantity of fat that has been also extracted from the bones by the steam. This is drawn off into cooling tanks, where, in its crude state, it is made into scouring soaps. By refining and adding vegetable oils and perfumes, toilet soaps are made.

The Making of Big Guns.

One of the chief sources of strength in big guns lies in the miles and miles of steel ribbon with wducTi the tube is reinforced. This ribbon, one-sixteenth of an inch thick and about a quarter of an inch wide, is wound round the tube or core of the great cannon. On a 12-inch gun about 130 miles of the ribbon is wound, a weight of fifteen tons. The ribbon has a tensile strength of 100 tons per square inch. From the time the ingots of steel, some of which are nearly 100 tons in weight, are taken from the steel foundry, where they are cast as octagonal masses, to w'hen, as a complete weapon, the gun is tested to prove its power and accuracy, scores of intricate processes are gone through. After being taken from the foundry, the mass of steel is dealt with by the machine-shop, where a hole is, made in each ingot in what is known as a trepanning machine. Under a hydraulic press of 10,000 tons power, it is next forged to reduce it to a tube or jacket of the required length and thickness of metal, . whereon it is passed to one of the ' large machine shops, there to be finished to internal and external diameters in machines ranging up to 180 ft in length. The tube is next reheated and tempered or hardened in oil-baths which are under the ground level and, of great depth, so that the tube may be suspended vertically in a bath while the "heat is steadily maintained at the required temperature by carefully controlled gas-jets. The tube is lowered into and lifted out of these baths by cranes capable of dealing with weights of 100 tons and with tubes 75ft in length; The same plant is used in the subsequent operation of building-up by the shrinking-on process the various tubes or jackets required to form the complete gun, the outer tubes being heated before being fitted over the inner tubes, so that with the subsequent contraction due to the reduction of temperature the outer tube tightly fits the inner. The innermost tube of all'is inserted as one of the later operations, and in very accurate machines the bore is rifled in order that the shot as it leaves the gun will have the gyratory motion essential to accuracy of fire.