Improvements in the Zoller Supercharger
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Modifications to the Lubrication System a Feature of the Latest Models of an Interesting Type of Compressor
INCREASING interest is being taken by commercial-vehicle manufacturers in the possibilities of supercharging, and a survey of this method of reducing the size and weight per horse-power of petrol and oil engines was published in our issue dated July 20. A concern which has made a close study of the problems of supercharging, and which has developed several interesting patents in this connection, is M. A. McEvoy (London), Ltd., Leaper Street Works, Derby, the maker of the Zoller compressor.
Several commercial-vehicle makers, both in this country and on the Continent, are, we understand, experimenting with this type of compressor, and certain alterations in design have recently been incorporated, notably to the lubrication system, to increase its reliability. As mentioned in OUT previous article, in the normal course Of events, failure Of the Supercharger 012 the road could only be occasioned by a breakdown of the lubrication sys
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tern, and it is interesting to note that the modifications recently made to tlae Zoller compressor are designed to reduce this possibility to a minimum.
A new and patented oil pump of the opposed-piston type has been developed and is now fitted to all Zoller' compressors. This pump is of simple design, and no cams or springs are used. The advantages claimed are that the flow of oil can be exactly metered in very small quantities, whilst the flow is maintained irrespective of whether there is a vacuum or pressure in the supercharger casing. Such bearings as are highly loaded are now chromium-plated by means of the Fescol process, and this has been found not only to reduce wear to a minimum, but virtually to eliminate the risk of seizure, in the unlikely event of the failure of the lubrication system.
A further modification is the inclusion of a balanced-feed lubrication system, whereby the oil is carried direct to the bearings by external pipes frorn a separate T joint in the centre of the supercharger. This joint is made integral with the case, so that the oil pipes have full support and may be free from fracture.
The Zoller compressor may be used for high-pressure supercharging, or, by means of a patented system of pressure control, a quite moderate induction pressure may be used throughout the speed range of the engine.
A wide range of models suitable for all types and sizes of engine is available, and a recent addition to the range is the M series, suitable for petrol or oil engines up to 12 litres capacity. On all types a ribbed casing is available if required.