Improved liners and a cooler piston
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SPRAYED coatings, applied to the external surface of a wet cylinder liner, that delay the onset of cavitation erosion, and a new technique for producing soluble cores for pistons that simplify oil cooling were included in the technical highlights of an open day for the Press on Wednesday at the research and development laboratory of Wellworthy Ltd., Lymington, Hants.
As mentioned by the chief metallurgists of the company, preventing cavitation is a simple exercise in that, for example, a coating of chromium can prevent erosion but it is significant that this treatment can transfer erosion attack to the crankcase. Included in the sprayed coatings developed by Wellworthy, and tested in the field, a nickel aluminized coating affords extended protection against erosion and because it is "galvanically noble" it caters for corrosion attack that is promoted by the scouring action of erosive attacks.
In comparison to the use of cast-in cooling coils or a two-part piston, the soluble-core method of producing oil cooling passages in pistons offers cheapness of manufacture and in due course should enable cooling efficiency to be improved.
The cooling galleries of the pistons are produced at the casting stage and because the cores are water soluble no sand remains in the casting of the finished piston. P.A.C.B.