About Oil retaining Bearings
Page 32
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New " British Bound Brook" Publication Listing Big Range of Diepressed Bushes in Standard Sizes TO commercial-vehicle manufacturers and makers of its auxiliaries and accessories much interest attaches to bronze bearings of the oil-retaining type, which are made by controlled high-pressure die-pressing of finely divided copper and tin, so -that the metal is porous and contains
about 25-30 per cent., by volume, of lubricating oil. A publication on the subject has just been issued by the British Bound Brook Bearing Co., Witton, Birmingham, which should be of value to designers.
It gives a list of all the different standard sizes of sleevetype bushes, thrust washers, flanged bushes, and spherical bearings, made of the eOncern's special Compo H porous bronze, which are finished to extremely accurate dimensions.
Bore diameters are within plus or minus 0,000. 5 in. of normal size, and other dimensions are within plus or minus 0.0001-0.0005 in. It is possible, moreover, to produce to even closer dimensions. As the bearings are die-pressed and made with tools carefully ground and lapped, no machining is required, whilst they are supplied with a mirror finish.
Before installing, all that is necessary is to dip the bearings into good-grade medium or heavy oil, which will wash off any dust or foreign matter that may be adhering, and provide sufficient lubricant to fill the space between the bearing and the shaft. The amount of oil in the porous bronze is sufficient to give lubrication for many years, that is in practice equal to the life of the bearing.
Listed in the publication are about 215 different standard sizes of plain bearing, commencing with the smallest, 0.093 in. inside diameter, 0.2852 in. outside diameter, 0.092 in. shaft 'diameter and 0.282 in. housing diameter, and finishing with the largest, which is 2.254 ins, inside diameter, 2.377 ins, outside diameter, 2.25 ins, shaft diameter, and 2.376 ins, housing diameter.
The maximum lengths in this wide range of standard bearings are 11 ins. for diameters from l ins. up to 21 ins., li ins, for over 1 in. up to li ins, diameter, and 2 ins, for all sizes up to 1 in. outside diameter.
With regard to shaft clearances, the recommended figures are given in a series of curves, reproduced herewith, varying frdm less than 0.001 in. to 0.0045 in. with shafts up to 5 ins, in diameter, referring to three standard conditions, ordinary driving, electric motors and self-aligning bearings.
Porous bronze flanged bushes are available in about 70 standard dimensions, varying from 0.165 in. bore up to 1.1819 ins. bore.
The composition of these oil-retaining bronze bearings fa 438 per cent. copper, 9.7 per cent. tin, 1.4 per cent. graphite, and 0.9 per cent, other material, the metals being in an extremely finely divided condition produced by electrolytic methods to ensure purity whilst, in spite of the porosity, the specific gravity is within the range of 5.8-6.5, and the crushing load is 70,000 lb. (Si tons) per sq. in., for all ordinary conditions being equal to cast bronze.