Carbon Canker

NZ Truth, Issue 1080, 12 August 1926, Page 16

Carbon Canker

Cause and Effect

117HILE deposits vary consider- . ably m appearance from powdery soot-like accumulations, which can readily be removed by wiping with a rag, to hard cokelike masEes, which are only with 1 difficulty chipped from the metal to which, they adhere, the chemi-. cal composition m ail cases is approximately the same. AS the name implies, they consist, chiefly of the element carbon, which is derived from the lubricating oil and the motor spirit used m the engine. . • There invariably is found a quantity of mineral -matter, such asoxidesr carbonates and silicates of iron, alumin-, ium, calcium, etc., which is derived from the road dust suspended m the air dx-awn m through the intake. . ■• ■ ;■ "; ''■;[■■ :■ ■ : : ; Where insufficient ' care ; has been exorcised to select the best ; position' for this intake, or. where .the air-filtra-ti.on device is inefficient, the amount of mineral matter often reache? astonishingly high percentages. Apart from- the fact that it increases the bulk of the deposit, much of this road dust is of a gritty,, abrasive nature, and its presence has very deleterious effects on bearing surfaces. The phenomenon of a casehardened steel gudgeon pin be- ' coming worn more, rapidly than the comparatively' soft small-end bush is due to a large extent to' the grinding the pin receives from ■:• particles of road dir,t. which have become 'embedded m the^bearing. , > The chief source of the matter m 'the deposits is .undoubtedVy the lubricating oil used m the engine, a small quantity of which finds its >vay up into the cylinder head, where, m the form of, a thin film '•'covering the walls of the "combustion • chamber and the piston crown, the lubricniit is sub-, jected to the 'fierce bent of the . burning gases" during the combustion period.