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connected directly with the link foot-such as the Baldwin engine built for the Rock Island Raiload, shown elsewhere in these pages—where the valve chest lies nearer the centre line of the engine than is usual; in such cases the link piece ia, ib, extends scarcely lower than its supporting brackets and there is no link "foot.” The trunnion, 3b, on the inner side is also dispensed with, while the outer trunnion is made considerably longer and extends through a sort of journal box in the manner of the common rocker shaft, and to its outer end is attached an arm, or lever, to the lower end of which the eccentric rod is connected at the same distance below the centre of the link trunnion, or fulcrum, as it would be if regularly connected with the link foot.
While the foregoing matter covers the standard method of application of the Walschaert valve gear by American locomotive builders, there are variations, and referring to Fig. 8, it is seen that Auchincloss—whose book on various valve motions is considered an authority-sets the eccentric a quarter behind the main-pin instead of ahead of it as is usual with outside admission valves; but he reverses the effects of that change by carrying the link-block at the top end of the link when the engine is to run forward. The reversing shaft is below the link (like the old-time Rogers engines were fitted), with the lifting arm extending backward so
that throwing the reverse lever forward raises the radius rod, and the valve's action remains the same as with the style of gear adopted by American builders that we have analyzed. The Auchincloss type is common on European engines.
Fig. 8.—Walschaert Valve Gear. (Illustration from Link
and Valve Motions.--Auchincloss.)
During the years that foreign railways have had the advantage of the use of this worthy device we have not been altogether blind to its merits: Certain progressive engine builders and master mechanics in America have endeavored to bring the Walschaert valve gear to trial, and some form of it was applied to quite a number of engines but never received a fair showing. Men were intrusted with setting-up the gear and maintaining it, and obtaining results from its use, that had found it the struggle of a half lifetime to master the mysteries of the Stephenson link motion, and, having learned it, placed an extravagant valuation on the mechanism that had been so hard for them
to thoroughly understand: and to find something better, that was as simple as the motion of Walschaert was hurtful to their self-conceit, and it was this priestcraft among railroad mechanics, and even officials, that choked down the honest endeavor of those who did try to improve that most vital part of the motive power of our railways. When William Mason presented a design of the Walschaert valve motion finely suited to the conditions of American locomotive construction, together with a paper detailing the good features of the gear, to the Master Mechanics' Convention in 1885, it met with a cool reception; in fact, without data of actual performance in evidence, the Walschaert motion was there generally condemned. The time was not ripe; they could afford to neglect it.
Shortly after this the railroad with which I was connected was supposed to have tested the merits of the Walschaert gear by putting that style of link, reversing gear, and combination lever on an engine that had been equipped with the Stephenson motion, but instead of connecting the Walschaert link with an outside crank on the main-pin, one of the old eccentrics on each side was used to operate the links, and thereby one of the best features of the device was omitted, and neither was it erected with reference to a scaled model. After a short time the old gear was restored, and there were no data afterward obtainable
to prove the success or failure of the half-constructed gear.
When it is decided to apply the Walschaert valve gear to any certain type of engine the design should be correctly laid out and constructed from a diagram, as the proportions cannot be tampered with by experimental changes without seriously affecting the correct working of the device. The only part capable of variation in length is the eccentric rod which connects the return crank with the link; this rod may be slightly lengthened or shortened, to correct errors in the location of the link centre, from centre of the driving axle which carries the return crank. This crank, representing the eccentric, must be permanently fixed to the main-pin, and the slightest variation in its position relative to the main-pin will be detrimental. When the engine is assembled, the throw of the eccentric should be checked up by the specifications, and any error should be at once reported in order that the mistake may be rectified by either correcting the position of the eccentric, or by a change in the design of the other parts to compensate for the error. It is probable that inattention to this absoluteness of detail required in the erection of the gear, as well as prejudice, is accountable for the condemnation of the Walschaert motion in the past.
Along in the early seventies the Mason Machine