Cylinder and Saddle. The cylinder and saddle for a simple locomotive, illustrated in Fig. 78, are constructed of a good quality of cast iron. The casting is usually made in two equal parts but it is not uncommon to find the saddle formed of one casting, each cylinder being bolted to it, making three castings in all. Fig. 78 illustrates the two-piece casting commonly used. The two castings are interchangeable and are securely fastened together by bolts of about 1¼ inches in diameter. The part of the casting known as the saddle is the curved portion A, which fits the curved surface of the smoke-box of the boiler. This curved surface after being carefully chipped and fitted to the smoke-box is then securely fastened to it by means of bolts. This connection must not only be made very securely but air tight as well, in order that the vacuum in the smoke-box may be maintained. In the cross-sectional view, the live steam passage B and exhaust passage C are shown. The steam enters the passage B from the branch pipe and travels to the steam chest from which it is admitted into the cylinder through the steam ports F. After having completed its work in the cylinder, it passes through the exhaust port G into the exhaust passage C to the stack. The cylinder casting is fastened to the frames of the locomotive as well as to the boiler. D and E show the connection of the saddle casting to the frame. In this case a frame having a double front rail is used, each bar being securely bolted to the casting.
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