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GEAR And Arguments for its Use as Against the Stephenson

Link Motion



And Arguments for its Use as against the Stephenson

Link Motion

(1) Accessibility. There is not room enough for the Stephenson gear under a very large passenger or freight locomotive. The eccentrics are crowded, and proper inspection, not to speak of proper care, is difficult, except over a pit. Valve gear to be properly maintained must be accessible for inspection and lubrication. The accessibility of Walschaert gear should reduce engine failures.

(2) Weight. A saving of 1,745 pounds is possible by using the Walschaert gear, in the case of a very heavy passenger engine. The Stephenson gear, weighing as much as two tons, is far too heavy to be satisfactorily reversed twice in every revolution on fast running locomotives.

(3) Directness. Walschaert gear transmits the moving force to the valve in very nearly straight lines, avoiding the springing and yielding of the rocker arms, rocker shafts, and transmission bars, which

cannot be avoided in these parts of the Stephenson motion, even if they are made very heavy.

(4) Permanence o, Adjustment. The advantage of permanence of adjustment lies with the valve gear which has no large eccentrics. This is proved by the statement of the Superintendent of Motive Power of one of the great trunk lines—a comparative statement covering the performances and condition of the valve gear of engines that differ only in having Walschaert vs. Stephenson gears. This statement appears in this book later on. All connections in the Walschaert gear are made with pins and bushings, which are designed specially to resist wear.

(5) Wear. Large eccentrics, besides occupying too large space, wear unevenly, and lubrication is difficult with the high surface velocities of the largest sizes. With hardened pins and hardened bushings the Walschaert gear has an important advantage in maintenance.

(6) Smooth Operation. Stephenson links, under the influence of two eccentrics, move through wide angles, resulting in a wedging action of the link-block, which strains the year when working hard, and produces lost motion. Walschaert links oscillate through smaller angles, producing less lost motion. The effect of this angularity of the links is plainly discernible on the testing plant.

(7) Frame Bracing. The removal of the valve gear from between the driving wheels facilitates bracing the frames of the locomotive laterally.

(8) Unvarying Advance of the Valve. Lead, if present, is not altered by hooking-up the link.

(9) The General Adoption of Walschaert Gear Throughout Continental Europe. Its use there for over half a century.

As to accessibility, everything is in favor of the Walschaert motion. The common link motion is crowded in between the frames where it is very hard to get at; the space that it occupies could well be used for o her purposes, and the valve gear requires too much attention to be stowed away in a somewhat inaccessible place. When break-downs occur on the road, time is lost in doing repair work, or in disconnecting, in the confined space inside the frame; and in the shop, the locomotive with the Stephenson gear requires considerably more time to have its valve gear set up correctly than does the engine equipped with the Walschaert motion. Imperfectly lubricated machinery is expensive, and the oil used on railroads represents a large sum annually. The double eccentrics require a large amount of oil, but their location invites carelessness in getting it properly applied, and the monthly strictures against the men as to the amount used results in an

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