Зображення сторінки

these pins and pin holes from wear is but slowly effected if kept well lubricated, and is one reason why lost motion is so slow to develop in the Walschaert valve gear. Just above the pin hole 4a there is an oil well finished in the top of the link foot, 1 inches in diameter by 1 inches deep, with a 1-inch hole drilled down from the bottom and through the bushing of the eccentric rod pin hole for the feed of the oil; a threaded cap nut is screwed into thetop of the oil well as a cover.

In section A the dotted arc lines 6a show the outlines of the opening, or slot, in the link in which the linkblock travels, and the faces of this link-slot is kept lubricated from an oil well in the top end of the link piece, this oil well being shown in dotted lines at 5a and 5b; it is covered by a cap nut that is a mate to the cover of the other oil well in the link foot, and has a threaded tap 1 inches in diameter. In section B, the left side of the link is turned to the outside of the engine, and the hole in the outside bracket at 7a and 7b is to permit direct oiling of the link.

The link-block is represented in sections C and D; C is the side view and shows the block in the position in which it would lie in the view A of the link,imagine the link-block C raised, following the arc of the link until it entered the slot shown by the dotted lines 6a. Taking an end view, if the link-block, as shown in the section D, should be placed in the slot of

the link piece of section B, it would be seen that its edges were almost flush with the sides of the link piece-extending only 32 inches out from each side of the link. It will be seen that the link-block contains an oil well, shown by the dotted lines at 9c and 9d, 1 inch in diameter by 1 inches deep, with a 4-inch feed hole from it down to the link-block pin.

The radius rod lies in an exact line with the link, but at its union with the link the radius rod is forked, its jaws passing, one on each side of the central link piece, and inside of the bracket sections at 00. There is a pin hole through each jaw of the radius rod by which it is connected to the link-block, the pin that passes through the radius-rod jaws also going through the hole 8c, 8d, of the link-block, and this hole is supplied with a case-hardened, wrought-iron bushing as a protection against wear; but there will be no wear to the holes through the jaws of the radius rod for the reason that a bolt runs down through a hole in each jaw and through the link-block pin, thus holding the pin rigid with the radius rod and turning only in the hole through the link-block. The openings 72, 76, in the outer link bracket, besides giving access to the link slot for oiling, may also be used as an aperture through which the link-block pin can be removed.

Certain types of engines are so constructed that the eccentric rod is not in line with the link and cannot be

[merged small][merged small][merged small][ocr errors][merged small][ocr errors][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small]

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 Auchinclosswhose 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

« НазадПродовжити »