File:Stephenson’s 2-2-2 Patent Locomotive of 1837 – Enhanced version with caption.jpg

Image is a scan of:
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.

Digitizer: The Internet Archive, 2014
Contributing Library: ASC - York University Libraries
Digitizing Sponsor: York University - University of Toronto Libraries

View Book Page: Book Viewer, Page viewer
About This Book: Catalog Entry
Click here to view book online to see this illustration in context in a browseable online version of this book.

Text Appearing Before Image:
22   The British Steam Railway Locomotive from 1825 to 1925
[...]
     Stephenson’s Six-wheeled Engines.—The Liverpool and Manchester Railway had been laid with very light fish-bellied rails, 35 lb. to the yard, and it was soon found that the later “Planet” class, weighing 9 tons total with 5½ tons on the driving wheels, was too heavy for the road. Moreover, having four wheels only, with the driving wheels in front of an over­hanging fire-box, they were some­what unsteady, in spite of the inside cylinders, though much of this unsteadi­ness might fairly be attributed to the permanent way. Pending the relaying of the latter with heavier rails, it was decided by Stephenson to add a third pair of wheels behind the fire-box. Edward Woods stated that the additional wheels were not intended to relieve the driving wheels of any great part of their load, but to check the pitching of the engine by taking a part of the weight at the time of plunging. The trailing springs there­fore carried a very light load. This was the origin of what was formerly termed “Stephenson’s patent engine,” which ran on six wheels, one pair being behind the fire-box. The 2-2-2 engine, thus produced, became a standard express passenger engine, and was built in this country from the end of 1833 until 1894.
     The first new engine of the type, named “Patentee,” was built for the Liverpool and Manchester Railway. An engine some­what similar to the “Harvey Combe” of 1835 but built in 1837, with several improvements, is illustrated by Fig. 17.⁷ A very full description of it is given in Tredgold’s “Steam Engine.” This description is worth careful study, since it shows in how very few essential details Stephenson’s locomotive of 1835 differed from that of to-day; in fact, the principal differences lay in the use of the old fork instead of the link motion, in the absence of sufficient lap on the valves for expansive working, and in the draw-bar attachment to the fire-box. Seeing that only six years had elapsed since the construction of the “Rocket” the progress made in design was truly wonderful.
     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.
———
⁷ Sometimes hitherto described incorrectly as the “Harvey Combe.” See THE ENGINEER, Sept. 24th, 1926, p. 330.

     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.
     It was a long time before the design of wheels settled down to anything approaching uniformity, and Stephenson’s wheels at this period differed consider­ably from wheels as we now know them. In the engines under consideration the hollow boss and rim were of cast iron. The rim was also made with a hollow groove round it to lessen the weight. The spokes were wrought iron tubes tapering from 2¼in. to 2in. diameter cast into the boss and rim, and arranged so that alternate spokes slanted in opposite directions. The tires of the driving wheels, 5ft. diameter, had a mean thickness of only about 1⁷/₁₆in.; all tires were of wrought iron, welded. The driving tires of Stephen­son’s engines had no flanges.
     The fire-box had water spaces 3½in. wide at the sides and 4in. wide at the front. The ⁷/₁₆in. copper plates were set in all round the fire-hole to meet the iron casting plates, and the two were riveted together by copper rivets. The pressure was 50 lb. per square inch. The arrangement of side stays was practically what it now is; the ¾in. copper stays were screwed full length and the ends riveted over. They were spaced 4in. apart.
     Copper tubes had been found to wear out very quickly owing partly to the effect of hard particles

24   The British Steam Railway Locomotive from 1825 to 1925
of coke. Hard brass tubes were suggested by Mr. John Dixon, then of the Liverpool and Manchester Railway, in 1833, and were after­wards used with much better results. These tubes in the engines under consideration were 124 in number and 1⅝in. diameter, ¹/₁₃in. thick. After having been soldered inside at the joint they were drawn through a circular steel die to make them truly cylindrical.
              image
              FIG. 18—STEPHENSON’S 2-2-2 ENGINE EXHAUST PIPE
They were ferruled at both ends with steel ferrules, iron having been found to wear more quickly.
     The blast pipe was of copper, 3¾in. diameter at the bottom and tapered gradually to 25½in. diameter at the orifice. The breeches pipe, which connected the cylinder exhaust flanges with the blast pipe, was provided with a small out­let pipe under­neath each of its branches (Fig. 18). These pipes united into a single vertical pipe with out­let at the bottom under­neath the cylinders and closed by a cock. Their original object was to drain the water from the breeches pipe. Edward Fletcher fitted similar cocks under­neath the steam chests of all the North-Eastern engines, on which they were in use until 1883; but their main object on this railway—at least in the eyes of the drivers—was to reduce the force of the blast by diverting part of the exhaust steam directly into the open air through the exhaust cock instead of through the blast pipe.
     In such engines as had no ashpans, and they were the majority, a butterfly damper valve was placed in the bottom of the chimney. The objection to ashpans was due to the custom of dropping the fire at the end of a journey by pulling out the fire bars.
     A steam dome on the fire-box was provided, since in the very early engines great difficulty had been experienced in preventing priming. The regulator was of the disc valve type and was placed in the horizontal steam pipe under­neath the dome. The disc valve faces were ground to form a steam-tight joint when the valve was closed.
     Feed pumps with ball clacks and worked from a direct connection with the piston-rods were used. The ball clacks were the invention of John Melling, of the Liverpool and Manchester Railway, on which they were introduced about 1834. The pumps were provided with pet cocks, which had been invented by George Stephenson.

Note About Images