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In the capacity of an air-brake instructor, it has been the pleasure of the author of this book to endeavor to impart information on other mechanical and general railway subjects, as well as those relating to his special profession, to the railroad men with whom business has brought him in contact, and since the tendency of locomotive builders has been toward the introduction of the style of valve gear that was invented by Egide Walschaert many years ago, and never taken up in this country through sheer conservatism until the force of combined circumstances compelled its adoption, the many requests for information concerning that special device have revealed the fact that while there are legion of books devoted almost wholly to the so-called Stephenson link motion, there was not one book in existence given wholly to the subject of the Walschaert valve gear, and nothing in print that explained that style of motion to the satisfaction of the locomotive engineer, the shop man, and the master mechanic, alike; in fact, no treatise could be found that extended further than an elementary

description of the gear, and this book is the result of a determination to supply the deficiency.

The American Locomotive Company, and the Baldwin Locomotive Works, have issued from time to time pamphlets illustrating and giving the general dimensions of their recently constructed engines, and they have very kindly permitted the use of many of those plates for the purpose of illustrating the text of this work.

In that portion relating to the laying-out of the Walschaert gear for any particular engine, from the designer's or the shop-man's point of view, I have quoted and borrowed several illustrations from the very able paper read at the 1906 convention of the American Railway Master Mechanics' Association, by Mr. C. J. Mellin, Designing Engineer of the American Locomotive Company. This paper was written on the subject of Special Valve Gears other than the Stephenson link motion, and contained in a condensed form an exposition of the Walschaert principle of valve actuation modified by the requirements of presentday railway practice and the improvements suggested by progressive American locomotive builders. The Baldwin Locomotive Works were of great assistance to the author in furnishing twin diagrams of the Walschaert gear in connection with valves of outside admission and inside admission that would undoubtedly

be the chief and most interesting features of any treatise on this type of valve motion that could be written, and are reproduced directly from the models used in designing the valve gear at the greatest locomotive works in the world.

It would be natural to presume that the reader of this book, with interest enough in the Walschaert gear to prompt him to make an effort to secure information in regard to that style of valve motion, would already be possessed of at least a fair working knowledge of the principles of the common valve itself; therefore, the valve is herein treated superficially, except in its actions that may be peculiarly induced by the motion of the Walschaert gear.





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