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THE WALSCHAERT VALVE GEAR
ANALYSIS OF THE WALSCHAERT VALVE
FROM the time of the building of the first locomotive engine, the methods employed to actuate the valve that is required to supply steam from the boiler to the cylinder, and discharge it therefrom after it has performed its work, were experimental and crude, until along about the year 1840 the double-eccentric hookmotion had naturally evolved into the shifting link action, under the name it has ever since borne--the Stephenson link motion; and in spite of our general lack of conservatism, that gear is, to-day, the vital part of practically all American locomotives, although our engines have increased in weight during recent years to such an extent that the necessary enlargement of the parts of the valve motion has given them a tonnage to be started and stopped twice in every revolution of the driving wheels that should have prohibited the use of such heavy reciprocating parts before now.
For this and other reasons, our locomotive builders have been casting about for some time in search of a valve gear more suited to modern conditions, with the result that many railroads have recently received new engines equipped with what is known as the Walschaert valve gear, a motion that was originated almost as long ago as the Stephenson link, and that has been in continuous and highly satisfactory use on European railways ever since; given desultory trials in America at intervals in the latter part of the last century by those prejudiced toward it, and dropped from sight, it has risen into our view again through a sheer necessity, and there is a general desire, now, to get acquainted with the principle of its operation.
About the year 1844—the transition period in the development of valve motions from the undecided to the accepted principles—Mr. Egide Walschaerts (the final s in his name has been dropped in its application to that type of valve gear), who was acting at that time as Master Mechanic of the Belgian State Railways, seems to have been dissatisfied with the results obtained from the use of two eccentrics in governing the motion of one main valve, and most likely foreseeing the possibilities in the line of economy by using the expansive power of the steam in the cylinders-something that had always been impossible of attainment with the hook motion-he invented the form of valve gear that bears his name, and to-day it is uncommon to see a picture of a locomotive belonging to any railway of any country in Europe, that is not equipped with the Walschaert gear,--monuments of power, they are, proclaiming the genius of the inventor of that most vital part of the locomotive. Europeans have made the most of this device and have brought out its best points, and it is worth while to note that in practically every case their engines use the D-slide valve-or, at least, outside admission valves--in connection with the Walschaert gear: There's a reason.
Born in the little village of Mechlin, near Brussels, in 1820, Walschaert was but fifteen years old when the State Railway lines were extended to Malines, where the main shops were located; but railway mechanics appealed strongly to the young man, and it is known that he was employed in the State Railway shops in 1842, and that two years later, as locomotive foreman, he had gained an enviable reputation as a successful railway mechanical engineer. It was not long until he was appointed chief superintendent of the shops, and having gained this advancement at a bound, being still a young man and a master at his craft, it is a fact that has never been explained that Egide Walschaert remained at just this level in his profession for the rest of his life.
Neither did he patent his own device. It seems