The properties of torsional vibrations reciprocating engine shafts.— Part I

Abstract

In a previous paper by the writer an examination was made of the torsional vibrations occurring in a reciprocating engine shaft. The case studied was that of a shaft driven by a six-cylinder engine, all parts except the shaft being considered rigid. Certain interesting results, arising from the action of the reciprocating parts, appeared. On account of the importance of the subject of torsional vibrations in engineering practice, and on account of the unexpected nature of the analytical results, it was considered of some interest to examine in greater detail the effect of the reciprocating parts in producing or modifying the vibrations. For this purpose a model is proposed which, it is considered, is as simple as can be conceived, and which, at the same time, involves the characteristics of reciprocating motion. The model is described and the analytical results obtained in Part I of this paper. To verify the analysis, the model was set up in the laboratory and the vibrations observed. Further, to simplify the experimental work, it was thought sufficient for the purposes of verification to arrange it in the first place so as to give only a qualitative agreement with theory, and therefore a precise quantitative agreement was not aimed at, and should not be looked for. An experiment on a much more refined method is being proceeded with to examine minutely into the numerical accuracy of the theory. The details of the present experiment and the numerical results are given in Part II.