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I n t e r n a l   C om b u s t i o n   L o c o m o t i v e s a n d   V e h i c l e s By S. M. Vauclain

HE steam locomotive has dominated transportation since its successful introduction approximately one hundred years ago. It has steadily improved. Its performance, through its greatly increased tractive power, has met the needs of modern transportation arising from the tremendous development of the world in the past fifty years. As a single self-contained power unit it is without equal so far as its general efficiency and low cost of production are concerned. Therefore, when discussing railway motive power, the standard of comparison must be the steam locomotive, which occupies a strongly entrenched position from both practical and sentimental viewpoints. Its simplicity, ease of control and action under widely varying conditions of load are factors that its rivals must embody if they are to successfully compete with it in every-day service. With the established efficiency of modern internal combustion engines before him, the designer of railway motive power is naturally attracted toward their possibilities of employment within his special field of endeavor. The Diesel motor shows an overall thermal efficiency as high as 33 per cent, while steam locomotive performance is

about 1/4 of this figure. But even with this handicap, the steam locomotive of today is a remarkably flexible and reliable travelling power plant. I n order to properly compete, no matter what the fuel economies may be, the internal combustion locomotive must approximate this same flexibility and reliability. It must have ease of control, ability to start a full tonnage train, and adaptability to the rapid change in physical conditions met in operation: such as variable speeds, gradients, curves and weather conditions. It must not be too complicated in detail nor too heavy per horse-power developed. Herein then are the basic features which the designer must constantly bear in mind. While a gain in thermal efficiency will warrant an increase in initial cost, the price must not be so prohibitive as to offset the anticipated gain in cost of operation. The problem naturally divides itself into two general classes of power:—self propelled vehicles for light traffic and locomotive units for hauling trains equal in tonnage to those hauled by steam locomotives. The first division offers easier accomplishment, because the power required is low and the weight of engine and transmission details, compared with the entire weight of the vehicle, will make possible an economical

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