Metal Research Means 'Big Benefits for vehicle design
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Progress is Rapid and Steady in the World of Metal Research and the Subject Becomes an Increasingly Extensive One
THE student of metallurgical progress finds himself bewildered by the multiplicity of the improvements made and the difficulty of coping with the spate of new inventions and discoveries issuing from the factories and laboratories of the world. Even those advances of direct interest to the commercial-motor industry are copious enough to fill a whole issue of this publication, if they were to be described in detail. All the more is it important, therefore, to condense and summarize, and in the following notes some recent developments are enumerated.
The development of complex aluminium-nickel-cobalt alloys for the manufacture of permanent magnets has led to the complete redesigning of magnetos, with the purpose of raising the output of power and, at the same time, lowering dimensions and weight.
Application of New Metals to Electrical Equipment.
In a magneto designed to take full advantage of these new materials, a one-piece rotor shaft is made from nickel steel, die-cast integral with the laminations and the magnets. The distributor-rotor insert is constructed from nickel-copper alloy, because of the high resistance to corrosion and pitting provided by this material. The magnets themselves are of " alnico" nickelcobalt-aluminium alloy, and the whole magneto is a masterpiece of design and efficiency.
Recent investigations have taken place as to the possibility of producing engines of an inexpensive character, relatively, but having higher power per weight-unit than existing engines. A cheapening of the production Cost of such engines was found to be effected by the employment of cylinders made from a special nickel-iron, having the following composition : 4.2 per cent. nickel, 1.2 per cent, manganese, 2.0 per cent. of silicon, and 2.8 per cent. carbon.
This type of iron has a Brinell hardness of approximately 300. It weighs a little more than a forged-steel cylinder would weigh, but the difference is only between 4 and 5 per cent. Wear resistance is high, and the cylinders are virtually unmachinabIe, without an annealing treatment. The physical properties and strength of this iron, and of the cylinders made from it, are excellent.
A most interesting development is the self-lubricating bearing. The basis of such bearings is a bronze of highquality chemical composition, containing .80-90 per cent, copper and 10-11 per cent. tin. This is in no way exceptional. What is astonishing is that by secret processes the metal is produced
820 in a micro-cellular state, and the interrelated cells are all charged with a good-quality lubricating oil.
This results in the continual presence of an oil film on the bearing surface, and this film increases in proportion as the pressure increases or the temperature rises. The film is of uniform type, and gives a more satisfactory lubrication than the addition of oil to the
normal bearing. It .is claimed that there is enough oil in the cells of the bearing metal to last for 750,000,000 revolutions, which is equivalent to many years of service.
The cellular structure does not lessen, to any great degree, the strength of the bearing, and a pressure of up to 4,000 lb. per sq. in. can be successfully withstood. No machining is necessary, owing to the fine limits worked to.
Gear wheels, in the past, have been forged, but a new development is their centrifugal casting. The gear blanks are centrifugally cast, which is claimed to employ a smaller quantity of metal, involve less machining and to create a gear which is more uniform and trustworthy in performance.
Employment of New Ferrous Alloys.
Valve-spring wire is being made from a steel containing 0.75-1.1 per cent, of chromium, and 0.15-0.3 per cent, of vanadium, whilst the new coppersilicon-iron castings are used for parts of commercial-vehicle engines.
This metal is claimed to possess an ability to withstand shock considerably higher than that possessed by steel forgings, which it satisfactorily replaces. The alloy has, however, to be given a careful heat-treatment. Gear teeth are being hardened, to-day, by the oxyacetylene flame, and although, at the moment, this process has not been applied to the smaller gears, it may develop in this direction.
Research into bearing metals for commercial-motor use has been intense. Big-end bearings have, for example, been made from a copper-lead alloy on steel backing, :lined both inside and out. It is claimed that the life of bearing S of this type is approximately five .1.,trOs that of white metal 'bearings..,
Cadmium additions have been made
to babbitt metals, and it has been discovered that this improves the ability of the metal to withstand failure caused by fatigue. Cadmium-nickel alloy are also being widely used for bearings. The copper-lead alloys referred to earlier are often alloyed with percentages of nickel or Manganese, in order to lessen the tendency to segregation.
Valves and valve parts are also being manufactured from a range of interesting materials. Nickel-chromiummolybdenum and nickel-chromium castiron valve guides, in combination with silicon-chromium valve stems, have been used, but the nickel-chromiummolybdenum irons are said to have the best wear resistance and resistance to " growth" when exposed to the exhaust flame.
The improvement in plating processes and materials is another subject for admiration. Recently, for example, a method of nickel-chromium plating, for parts of commercial vehicles subject to corrosion, has been discovered.
Materials for Components in Major Units.
Gears are being made from stampings of an air-hardening type of nickel-chromium steel, and connecting rods and caps from a 1 per cent. nickel steel. Cylinders are being made from heattreated cast iron, containing silicon, chromium, nickel, and molybdenum, which appears to present a trustworthy and uniform performance in use.
Gears, shafts, and dog clutches are being manufactured from a 4.25 per
cent. nickel-chromium‘molybdenum case-hardening steel; forks from.a casehardening or direct-hardening 3 per cent, nickel steel, and controlling gearbox mechanism from corrosion-resisting steel.
Various new alloys are being experimented with, among which may be mentioned those containing 87 per cent. nickel, 3 per cent, copper and 10 per cent. silicon. Another type is of nickel andcopper in virtually equal percentages, with an addition of approximately 2 per cent, of silicon. Another material which has its advocates contains 95 per cent. copper, 4 per cent. nickel, 1 per cent. silicon. Some of these alloys have been successfully used for valve seats. The applicability of others to commercial-motor use is, at present, in only the experimental stage.
The bodies of commercial vehicles are being made from a high-tensile nickel-copper steel, which not only resists the corrosion caused by weather conditions, but also saves a good tleal of weight without any, loss in strength.