SUBSTITUTES

Evening Post, Volume XCVII, Issue 103, 3 May 1919, Page 13

SUBSTITUTES

ELECTRICAL PROBLEMS

SOME GERMAN SOLUTIONS.

In the course of an article on the wartime shortages of metals, the engineering! correspondent of the London Daily Telegraph writes: —

Evidence has not been lacking of the grave consequences which threatened many German industries apart from considerable success in the discovery of substitute materials. With reference to some of these alternative materials and methods, we can safely' anticipate a reversion to previous procedure when circumstances permit. Others, however, will be of longer duration. In every department of engineering work has the enemy been forced to adopt expedients which, but a few years ago, would have been deemed outside the range of practicability. In the supply of materials required in the manufacture of essential steels of high grade the closest watch had to be exercised and new methods resorted to. Lubricants, rubber, leather, and many other materials became equally subject to restrictions of an order which necessitated' the use of other than the usually accepted materials where this was possible. Thus this march of substitution penetrated every corner of industry.

The electrical industries of Germany have experienced an increasing difficulty in procuring supplies of metals and other materials during the war, but, bearing in mind the thoroughness and vigour with which their engineers attacked technical problems in the past, we should naturally expect to find that much valuable work had been done with a view to providing as effective substitutes as possible for the formerly indispensable materials, supply of which had practically ceased as a result of our blockade. We are now learning from the testimony of engineers of neutral countries, who have been able to keep in touch with Gefman_ electrical engineers, somewhat of the special problems which arose, and the manner and degree of success of the Teutonic solution.

The whole of the available copper :n the country was needed for military purposes, and very little aluminium also could be obtained for ordinary industrial use. The only materials which were available in any quantitiy for cables and other electrical conductors wore zinc and iron. Up to the present time the former material had only been employed for electrical purposes in primary batteries and some forms of lightning arrester, as it has less than orie-third of the conductivity of copper, and is not readily drawn into wire. However, as zinc was fairly abundant, the resistance of the conductor could be easily reduced by using a larger sectional area, and after some research it was found possible to obtain" zinc wires of moderate strength, and a method was devised of reducing the rather high temperature coefficient. . Aluminium was naturally preferred when it was procurable, but as the insatiable military demands increased, more and more zinc was used, and this unusual substitute eventually appeared as bus-bars of generating stations, and even as windings on electrical transformers and motors. Wires of zinc were employed as aerial conductors for power systems, and the same material was pressed into service for the contacts of wall plugs and switches of a moderate capacity. Circuit breakers and regulating resistances, and much small apparatus in. which conductivity was not of supremo importance, also made use of zinc.

Aluminium was used very sparingly in the pure condition, .but three alloys proved of great service, and were used in large quantities: magnalium, which contains 90 per cent, of aluminium and 10 per cent, of magnesium, duralumin with 91 per cent, of aluminium and 9 per cent, of copper, and finally electron, which contains 10 per cent, of aluminium and 90 per cent, of magnesium. These materials were .used for bus-bars in generating and sub-stations. Lead, nickel, and tin were obtainable only in small quantities, but iron was plentiful, and appeared in the form of bus-bars and cables. In the latter case a small steel wire with an outer casing of copper or aluminium was oftenemployed, and experiments were made to replace the usual tin covering by one of zinc or copper to prevent atmospheric action. The use oJ zinc for the -windings of transformers and other electrical machinery naturally reduced the efficiency of operation, but it would seem to be possible to substitute zinc for copper with some advantage in the construction of switches carrying large currents. There was also a scarcity of satisfactory insulating materials, supplies _of rubber, cotton, jute, mica, and oil being very small. Regenerated rubber and a, number of more or less satisfactory substitutes were used, and doubtless increased the anxiety of those responsible for the maintenance of supply. Mention is made of a new substance —Faturan, which is said to be non-inflammable, nonhygroscopic, and unattacked by acids. Towards the end of the war all underground cables were paper insulated, protected by the thinnest lead sheath that could be used with any pretence of safety. Tho usual impregnating oil was replaced by an improvised substitute which appears to have given trouble on account ot its volatility. On the whole, no startling discovery has resulted from the efforts of German electrical and chemical engineers to overcome the difficulties which arose in the electrical' industry, and there is every prospect of a return to the materials of pre-war practice as soon as they are again available.