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Aviation History
1964
1964 - 0403.PDF
254 FUGHT International, 13 February (944 INDUSTRY International Products Company News Great Britain Hoffman Miniature Ball Bearings Facili- ties for the production of miniature ball bearings in large quantities have been established at the Stonehouse, Glos, factory of the Hoffman Manufacturing Co Ltd. Smallest of the standard range has an over- all diameter of 3mm, a bore of lmm and width of 1mm; balls 0.02in in diameter are fitted, and weight is 0.004oz. Cleanliness in manufacture is obviously of prime importance. All components—races, balls and cages—are ultrasonically cleaned and rigorously inspected before being assembled in a clean-room. A complete range of miniature bearings is manufactured. First there are the standard bearings for general engineering appli- cations, produced to the tolerances specified in BS 292:1958. For instruments and other applications where accuracy is of prime importance, precision bearings are supplied which conform to ABEC 5, 7 and 9 and BS EPS and 7. Finally, close-tolerance bearings are made which have to be tested to ensure that the starting torque required to initiate rotation does not exceed specified limits. These bearings are used in synchros and gyros and for stable platforms in inertial navigation systems. A typical test carried out on such bearings is to check that the starting torque is less than 0.4gm/cm when the bearing is subjected to an axial load of 400gm. The inner and outer rings and the balls of many of these high-precision bearings are machined from a high-carbon chrome alloy steel. Produced to a Hoffman specification, the steel is similar to BS EN31 (SAE 52100). It is a fully hardening steel and bearing components are heat treated to a hardness of approximately Rockwell C62. Such bearings possess dimensional stability up to 130°C. Where higher operational temper- atures are encountered, components can be Typical miniature hearings from the new Hoffman range referred to above heat-treated to give dimensional stability up to 225CC. Bearings required to operate in corrosive conditions from which they cannot be fully shielded, or at temperatures in excess of 225 °C, are manufactured from corrosion-resisting steels such as AISI Type 440C. Miniature bearings may be supplied with or without cages. These cages are pressed in one piece from either brass or stainless-steel strip to specification BS ENV56A. When equipped with a cage the smallest standard bearing (3mm diameter) contains seven balls; without a cage the same bearing contains 12. New Conduit System Rist's Wires & Cables Ltd, of Newcastle, Staffs, announce that they have perfected a new lightweight conduit system for the protection of elec- trical wiring on jet engines and aircraft. Easily assembled and dismantled, it super- sedes the older-type moulded harness and, while being readily accessible, is stated to give complete protection against ester-base fluids, oil, air and water. Its appropriate parts, of p.t.f.e. and other materials, are heat-resistant, apart from their excellent electrical properties. An important feature of the system is that it can be adapted to all situations in which enclosed wiring is essential. Titanium Prices Fall Increased demands for titanium, in both the aircraft and other industries, has led to more economic use of expensive titanium-processing plant in Britain. Consequently, the two companies producing titanium in Britain were recently able to reduce prices. Imperial Metal Industries (Kynoch) have reduced prices by about 4 per cent for sheet and 4-7 per cent for rod and billet. Certain grades of tubing are now cheaper by some 30 per cent. Jessop-Saville, of Sheffield, have made their eighth price reduction in as many years and, in addition to increased demand, find improved manufacturing techniques have enabled the reduction to be made. Again, the size of the cut varies according to the form in which titanium is supplied but ranges up to 7i per cent. New British Standard The new standard G 183 covering interconnections in ana- logue data transmission systems in aircraft has been published by the British Stan- dards Institution. G 183 is designed to ensure uniformity of interconnections in control and indicating systems in aircraft using analogue data transmissions. It covers the use of synchros, potentiometers Servicing gyros in the new super-clean area of Elliott-Automation's Aviation Service and Repair Division at Rochester, Kent. The division recon- ditions equipment from all over the world and maintains an on-demand 24-hour exchange service for all instruments manufactured by Elliott and its affiliated companies and so on, but does not deal with energizing volts, transformation ratios or accuracy of volts per degree. Requirements are gener- ally in line with relevant Arinc, EEA, MoA and SAE publications on the subject. Copies, at 10s each, can be obtained from BSI Sales Branch, 2 Park Street, London Wl. About Rubazote A new booklet describing the properties and uses of Rubazote and containing samples of the various grades and standards of the material is now avail- able from the manufacturers, Expanded Rubber & Plastics Ltd, of Mitcham Road, Croydon, Surrey. Rubazote is a soft expanded natural, neoprene or silicone rubber, with a closed- cell structure. Its resilience makes it suitable for a wide range of applications, including ejector pads, gaskets, discs and washers, tubes and cords and all types of dust-, water- and air-tight seals. The expanded neoprene is stated to be oil- and petrol-resistant, effective over a high temperature range and resistant to light and ozone attack. The expanded silicone rubber has high heat stability and will withstand continuous exposure to temperatures of up to 200 C.
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