File:Stephenson’s 2-2-2 Patent Locomotive of 1837 - crank axle.jpg

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Anonymous: “STEPHENSON’S 2-2-2 PATENT ENGINE OF 1837.” FIG. 17 in Ernest L. Ahrons, The British Steam Railway Locomotive, 1825–1925, London: The Locomotive Publishing Company Limited, and New York: Spon & Chamberlain, 1927, p. 23.

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22   The British Steam Railway Locomotive from 1825 to 1925
[...]
     A few of the more important details may be mentioned here. The outside sandwich frames (see plan, Fig. 17) were attached by brackets to the smoke-box, to the middle of the boiler, and to the fire-box. The engine, however, “pulled through the fire-box,” the draw links being attached to a channel bracket riveted to the back of the casing. There were two inside plate frames with driving axle guards welded on, and a fifth bearing was provided in a Y centre stay.
     The cylinders, 12in. by 18in., were encased within the smoke-box and were not attached directly to the frames, a feature already mentioned in connec­tion with the “Planet.” The steam chests were separate from, but bolted to, the tops of the cylinders, and all steam joints were made with gasket or canvas covered with red lead and oil. The valve spindles were connected to the valves by means of a rectangular wrought iron frame or buckle dropped over the valve as in present-day practice. The slide valves had ¹/₁₆in. outside and ¹/₁₆in. inside lap to ensure that the steam port was completely closed before the opposite steam or the exhaust port was opened. Lead was given to the valve, but there was as yet no real attempt at expansive working. The slide valve in two parts with short straight ports had now been abandoned. The piston rings consisted of one broad outer and a similar inner ring, which were turned exactly to fit the cylinder and each other and cut through in one part, having been first hammered a little all round on the inside to make them press evenly against the cylinder walls. Bent springs of flat steel were placed inside, behind the rings, to regulate the pressure as the latter wore down.
     The gudgeon pins had spherical journals on which the brasses of the connecting-rod small ends worked, and allowed for any slight deviation from square­ness of the connecting-rods. The spherical gudgeon pin bearings reappeared in 1907 on some Midland engines, more than seventy years after their use by Stephenson.

     1830–37   23
The crank pins were turned in the same manner as is done to-day, that is, by chucking the axles in cast iron blocks fixed on the ends and having balance weights, the lathe centre pops in the blocks corresponding with the crank pin centres. The crank pins for 12in. by 18in. engines were 5in. diameter by 3in. long, journals 3⅛ in. diameter by 5in. long, and wheel seats 5¼in. diameter by 7½in. long. The fore gear excentrics were fixed in the usual position near the middle of the crank axle, but the back gear excentrics were placed between the inside frames and the driving wheels, imme-

Text Appearing After Image:
              FIG. 17—STEPHENSON’S 2-2-2 PATENT ENGINE OF 1837
diately behind the bosses of the latter. A long transverse rocking shaft, which extended across the engine above the slide bars, actuated the valves. This arrange­ment of valve gear was used on many of Stephenson’s engines until 1841. The separation of the fore and back gear excentrics allowed room for a centre bearing on the crank axle.

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