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The purpose of this paper is to present information gained from a study of the lubricating oil aspects of crankcase explosions. Experimental tests indicate the crankcase atmosphere of a Diesel engine is a potentially inflammable mixture of oil mist and air in which ignition may be initiated by an overheated part. The minimum ignition temperature of an oil mist/air mixture is reduced by decreased air flow, increased mixture temperature, and increased ignitor size. No significant differences were found in the minimum ignition temperature of a wide variety of lubricating oils, even when diluted with up to 20 per cent Diesel fuel. As long as inflammable lubricants are employed, it appears that little can be done from a lubricating oil or fuel standpoint to prevent crankcase explosions. It is indicated that the problem may best be attacked by further critical studies of operation and maintenance practices and continued refinements in engine design.

THIS paper describes the important factors that must be considered in a study of engine power loss due to combustion-chamber deposits. Dafa are presented to show the effects of fuel composition, sulfur and lead concentration, and lubricant composition, engine design, and operating conditions on deposit power loss. The influence of engine operating conditions existent during the accumulation of deposits, and the importance of the engine conditions selected to evaluate the magnitude of the deposit power loss are illustrated. It is indicated that deposits cause power loss by thermal and physical restriction of the intake charge, and by reduction of thermal efficiency. It is concluded that differences in effect among the majority of commercial fuels and lubricants are probably small although relatively large differences may exist in certain critical engine applications. The engine operating conditions under which the deposits are accumulated are a major factor in deposit power loss.

ALL-HYDRAULIC buses, with power-operated control devices and auxiliaries, are now operating in three American cities, and winning a favorable response from passengers and drivers, as well as from maintenance mechanics, according to the author. He describes the new design features of these buses, their complete hydraulic power actuation, and explains how it is accomplished. Although power steering appeals to drivers, and dependable efficient operation of the hydraulic system makes the bus desirable from the purchaser’s point of view, the author believes that eventual savings in maintenance costs will be the factor which will place the all-hydraulic buses in a preferable position. He also points out certain features which can be advantageously incorporated in trucks at the present time. But he agrees that the situation in regard to trucks presents complexities that will not arise in relation to buses, which have a concentrated radius of operation and more unified service facilities.