Multi-section Bearing Reduces Friction
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A REDUCTION in friction of 20 per 1.-1 cent and increased resistance to vibration are claimed for a new type of
restricted clearance journal bearing known as the Camella, which has been developed by Cammell Laird and Co. (Shipbuilders and Engineers) Ltd., Shipbuilding and Engineering Works, Birkenhead. Although the bearing has been mainly applied to marine gear cases, the company is confident that it has a potential for road vehicle applications, including, for example, the transmission systems of heavy lorries. It is particularly recommended for diesel-engine camshafts and turbocharger rotors.
The bearing essentially comprises a number (normally three) of mutually eccentric bores with their centres displaced 120° on a circle having a radius equal to the eccentricity required. There are, therefore, three points of minimum clearance producing " multi-reactive" forces which centralize the journal, increase resistance to oil-film and journal whirl and give quieter operation. In marine installations use of the bearing has reduced vibration amplitudes by 80 per cent and has provided a substantial improvement in gear wear. Also of .importance in some applications, the bearings offer more exact alignment of co-axial components.
Although Camelia bearings restrict lateral freedom of the journal, they can accommodate an increased rate of oil flow, which is favourable to heat dissipation and load carrying. The minimum clearance allowable is determined by the diametral expansion of the journal. Because of the comparatively large difference between the maximum and minimum clearance of each section of the bearing, wedge action of the hydrodynamic oil film is increased.
P.A.C.B.