ENGINEERING NOTES.

Lyttelton Times, Volume CXVII, Issue 18066, 5 April 1919, Page 4

ENGINEERING NOTES.

A FLOATING ELECTRIC POWER STATION. One of the many British *■ freak” vessels produced during the war is tho floating electrio power station, officially known ns O.D. 258. Although it is formally a ship, it was under the control of tho War Office, not the Admiralty, having been secured for tho service of the Directorate of Inland Waterways aud Docks. Its function was to supply electrio current as and where required for the miscellaneous operations of this Department in connection with docks, harbours and canals used for military transport. At a distance this vessel might pass for a gunboat without guns; technically it is described as a steel barge. Amidships is a comploto electrio power station of 1000 liorse-powor, designed . so that practically any type of electrical installation can be fed from this source. Two oil tank 3, each with a capacity of twenty tons, and an electrically driven workshop with lathe, drilling machine and other repair plant, complete the main part of the equipment. . While this “ universal electric provider ” is tho direct outcome of war conditions, similar equipments are likely to be very useful in tlio construction of sea and river works. Tlioy are also worth considering for the permanent supply of electricity to rivorßido towns, where, owing to the nature of the subsoil and other local conditions, an ordinary power station would be difficult of erection on a site convenient for water and fuel supply. In remote parts of tho world a floating oil-power electric station could probably be Installed and run much more cheaply than a land station. BIG POTATO CROPS WITH ELECTROOULTCJRE. Striking experiments in electroculture were carried out by the South Wales Electrical Power Distribution Company, during 1917 and 1918, ou a two-acre plot of ground near Jfontypridd. As regards ploughing and manuring, the whole plot wa3 treated alike, bub electroculture was applied to only a portion of the ground, the remainder serving as a “ control ” for the purposes of comparison. Potatoes wero planted under precisely similar conditions over tho whole area, and during 1917 the electrified portion yielded a crop heavier by 17.2 per cent than that of tho control portion. In 1918 tho increase out of electroculturo was 12.6 per cent, the reduction being explained on several grounds, such, as that a smaller area of electrio wires was used and that part of the controlled plot hau had the benefit of electrification in tho previous year. Experiments were also mado with oats in an adjoining field, and although they were not carried out very thoroughly they point to an increase of 25 per cent in grain and 17 per cent in straw. On illid potato patch the wires wero first arranged as a 6ft rectangular network supported on insulators 6ft 6in from the ground; in August, 1917, the height was reduced to sft. During the 1918 experiment the wires were spaced 9ft apart, with no cross wires, and wero kept about two foot above the haulms. The network was fed through a transformer and rectified with a current at between 30,000 volts and 39,000 volts, according to the degrees of weather; the amount of current taken varied from 2.5 milliamperes in dry and from 4 to 7 in wet weather during 1917, and from 0.35 to 0.8 during 1918. Tho apparatus never failed, even in tho wettest of Welsh weather. On dark nights the wires could be seen glowing, and even the tips of the grass in the rectifier were touched with light. Insects seemed to avoid the wires, hut occasionally they settled on the net works, whore they glowed and were electrocuted. Although the voltage is so high, the current is so low that there is no danger to anything but insect life. Horses are extremely susceptible to electric shock, hut- one which broke into the network retired undamaged, although carrying a good deal of wire with him. These experiments confirm 'the promising claims 'made Uor this annlication of electricitv to agriculture which is being carefully studied bv a snpoinl sub-eommittee of the British Board of Agriculture. PREVENTING THE GROWTH OF CAST HtON. Amongst the • fascinating problems which make engineering science at once a most exacting and a most fruitful study, the characteristic behaviour of metals under varying conditions provides many curious cases. For example, grey cast iron grows appreciably in volume when exposed to high temperature. This characteristic, which causes much trouble in cast dies, valvo seatings and other parts, is believed to be duo to internal oxidation caused by tho penetration of hot gases into tho metal. A remedy recently suggested in England is to eliminate free graphite from the surface of tho metal, this being tho cause of its porosity. Successful results have been obtained by annealing the parts for several days in iron nist at a temperature of from 1650 to 1830 degrees Fahrenheit. WIRELESS FOR ALL OOMD4ERCIAL AEROPLANES. On© essential to the development of a long-distance aeroplane service for passengers, mails and parcels delivery is tlio use of wireless telegraphy. All the aeroplanes used in this service will, like everv large ship, carry wireless and an efficient operator, thus making it possible to send telegrams from any part of the world, on sea or land, to tho aeroplane during its voyqgo. The aeroplane will also receive regular messages regarding the weather conditions in '.he regions towards which it is heading, and will therefore bo able to adjust its course to avoid fog and other dangers. It is curious that one of tho first things to be transported over n long distance by aeroplane is a British wireless installation. Arrangements wero rcc(f:it\y madlo for the erection of Marconi wireless stations in remote parts of China—on© on the frontiers of Cashmere and tho other on the Chinese sido of Siberia. As there is neither road nor rail available in these regions, the Marconi Company arranged for the transport of the plant by a large Handley Page aeroplane. IMPROVEMENTS IN STEELMAKING. Amongst war-tiino research work, tho benefit of which will bo permanent, better control of the heat treatment of steel promises valuable results. It is now widely recognised that comparatively few degrees variation in the temperature makes all the difference in the properties of the finished material. The difficulties are particularly groat W'hero large masses of steel are concerned because it is difficult to secure the same temperature at the surface and in the mass of the metal. Other difficulties are introduced by the different scaling tendencies and different emissivities of various steels. Recent improvements in furnace construction facilitate the attainment of uniform temperatures, and tlio means and methods of pyrometry have been developed to such an extent that the most delicate heat treatment, can bo given with almost mathematical certainty and on the basis of a commercial repetition process. It was suggested recently by Dr Carpenter, at Sheffield, that working temperatures would be laid down in specifications for steel products in the near future. A start has already been made, and the state of practice is such that this policy is sure to be extended.