File:The railroad and engineering journal (1887) (14571858087).jpg

Identifier: railroadengineer62newy (find matches)
Title: The railroad and engineering journal
Year: 1887 (1880s)
Authors:
Subjects: Railroad engineering Engineering Railroads
Publisher: New York : M.N. Forney
Contributing Library: Carnegie Library of Pittsburgh
Digitizing Sponsor: Lyrasis Members and Sloan Foundation

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large circle with a small arc at c. It will thenbe found that in moving from « to i5 that the crank has turned22 degrees. Proceeding as before, the line b T will be laiddown in fig. 58 in the same position as in fig. 57, and an angleb T c, equal to 22 degrees, will be laid off from b T. Then theintersection oi c T with the circle at n will be the position of thecenter of the eccentric when the piston has moved 8 in. of itsstroke. In this way we may proceed and lay out the position of theeccentric for each position of the piston shown in figs. 15-22,or for the corresponding position of Ihe crank represented bya, b, c, d, e, f,g, h, i,j, k, and /in fig. 55. This has been donein figs. 56 to 69, and if the reader will draw a similar series ofdiagrams it will probably give him a clearer idea of the actionof an eccentric than he can get in any other way.* * In drawing such a series of diagrams, it will be_ best to make them to alarger scale than they are represented in the engravings. •
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Vol. LXII, No. I.) ENGINEERING JOURNAL. 37 Question ii8. Hoiu can the movement and the action of avalve be shown most perftclly on paper ? Answer. By drawing a diagram—tliat is, by representing ihievalve in a number of the positions it occupies in relation to thesteam-ports during a complete stroke of the piston, .ind thendrawing what are called motion curves through the inner andouter edges of the valve in each one of the positions in which itis represented. As such curves are in a sense purely imaginary,and do not represent any object on an engine, it is difficult toe-xplain clearly their nature and purpose, and perhaps stillharder for those with little or no knowledge of drawing tounderstand an explanation, no matter how clearly it may be•written. The reader must, thereiore, expect to give close atten-tion and perhaps some hard study to the following descriptionof this method of showing the movement of a slide-valve, in rt- represent a rocker, T the center of the main shaft, an

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