Page:Popular Science Monthly Volume 89.djvu/280

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��Popular Science Montldy

��on the bearings and the deli\ery of power in the wrong direction. A trip to the repair shop ine\itably ensues, with a big bill.

An oil which has not been selected with a due regard for the requirements of the cylinders is bound to affect the bearings. Unnecessary wear of the main or connecting rod bearings is caused by poor quality of the oil, or by an oil too light in body, or by an oil too heavy in body to reach the friction surfaces, or by an oil unsuited to the method employed for supplying it to the bearings. When each revolution of the crankshaft is accompanied by a dull thump, you may be sure that this wear is manifesting itself.

Selecting the Right Kind of Oil

The lubricating system of the auto- mobile ought to be but is not standard- ized. No less than ten different mechan- ical methods of lubricating automobiles are in use on the various cars made in the United States. Some day the Society of Automobile Engineers will specify one lubricating system for all makes of cars, and when that time comes it will be easier than it is now to select the right kind of oil. As it is the lubricating requirements of each make of car must be studied — a study which involves the construction of the engine; horizontal, vertical, or V type of cylinder arrangement; two or four stroke cycle; bore and stroke; valve construction and arrangement; oiling system; num- ber and fit of piston rings; piston clearance; condition of the bearings; cooling system (air and water); engine speed; and climatic conditions. It is evident that the average automobile owner cannot be expected to have either the engineering experience or the tech- nical knowledge required to consider all these factors. Fortunatch- the leading oil refiners have made elaborate and special studies of the many motor cars on the market and ha\e prepared lubricating charts, which can be obtained for the asking and which show exactly what oil should be selected for any given make of car. In a few years from now lubricating systems may be stan- dardized with the result that a single oil will answer fnr all motors.

��A -well-known motor car manufacturer has given it as his opinion that fully seventy-five per cent of automobile repairs and fifty per cent of depreciation in automobiles may be attributed to poor lubrication. A car costing $850 is operated at an annual cost of $416. Of this sum depreciation, repairs, and fuel are represented by $286. The amount of lubricating oil required in a year does not cost more than $10. It is the wildest kind of folly, therefore, to save money on the small amount of lubricating oil required to keep down the expense for re- pairs and depreciation. Cheap oils mean repairs, and repairs mean hea\"y bills.

��Spontaneous Explosions Due to Microscopic Plants

EVERY little while an explosion oc- curs in a subway, sewer or trench or in an electric-wire tunnel or some other subterranean conduit or passage- way under such circumstances that it is exceedingly difficult to determine the cause of the accident satisfactoriK-. Such explosions have often been attrili- uted to sewer gas, which contains a considerable proportion of methane and hydrogen. These gases are exceed ingU- combustible and quite capable of explod- ing with extreme violence when mixed with air in the right proportion and fired with a spark or a flame. This much is quite generally admitted; but in many cases the difficulty is to account for the ignition of the mixture, when it appears to be impossible to ascribe it to the action of any recognizable external agent, such as electricity- or flame.

It is well known that, during the de- coinposition of the organic matter in sewage, microscopic plants of a certain kind grow in the mass and act upon it in such a wa\' as to cause about two- thirds of it to liquef\', while the remain- ing third remains in the solid stale. When the conditions are faxorable, phosphine gas is occasionally generated in the course of the bacterial action; and this gas, when impure, has the peculiar and unusual property of taking fire spontaneoush- upon coming in contact with the air. Such a fire spreads with great r.qiidilN'.

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