York, Newcastle, & Berwick 2-2-2 Locomotives in Great_Britain

Class 185 (Locobase 3043)

Data from Ahrons (1927).

Symbol of Robert Stephenson's secession from the low-pitched boiler advocates, according to Ahrons. Stephenson had stated recently that he'd been for a ride on a high-pitched engine and such was the quality that he no longer believed that steadiness could be attributed to a low center of gravity. Ahrons also notes that the engine had its valve chests outside the frames along with the valve gear eccentrics. Although the steam chests were more accessible, they were likely to crack from the stresses of exposure to cold air.

Class 3-cylinder Stephenson/Howe (Locobase 11292)

Data from August Perdonnet, Traite Elementaird des Chemins de Fer, Tome Second (Paris: Garnier Freres, , 1860), pp. 551-555 and from J Snowden Bell, "Individual Paper on Three-Cylinder Locomotives," Report of the Proceedings of the Annual Convention of the American Railway Master Mechancics Association Held at Atlantic City, NJ, June 11, 12 and 13, 1913 (Chicago: Henry Shepard and Company, 1913), pp.247-248. Boiler pressure is an estimate.

Robert Stephenson and William Howe took out patent 11086 in 1846 for this interesting simple-expansion, three-cylinder layout. (Howe did not patent the link motion originally called the Stephenson-Howe motion, alas, although he doesn't seem to have regretted not garnering the royalties it would have earned.) The goal of this design was, according to the patent, ".. to counteract or neutralize all tendency that the oblique action of the several connecting rods on their respective crank pins may have to produce a lateral vibration or rocking motion of the locomotive engine from side to side on its supporting springs when it is traveling very rapidly."

All three cylinders were fed directly from the regulator through a steam pipe that had a tridentine fork in the smokebox. The two smaller outside cylinders had a longer stroke than the larger inside cylinder; the dimensions of the two outside cylinders taken together yielded a cylinder volume exactly the same as the single inside one. The outside cylinders drove on cranks on the hub outside while the inside cylinder drove the crank axle. Two sets of valve gear operated the three cylinders: on the left and inside the double frame was the large-piston slide valve. The second valve train operated the two slide valves mounted inboard of the small cylinders.

Bell quoted Daniel Kinnear Clark's description of the resulting harmonious motion and its effects: "As the movements of the reciprocating masses acting out of the center line of the machine, exactly balance each other, the tendency to sinuous action is removed, and fore and aft action alone remains'to be balanced. This engine, accordingly, runs with very superior steadiness, even when unassisted with balance weights in the wheels; and from its peculiar arrangement, it is susceptible of a very perfect equilibrium. It is found to give unqualified satisfaction on the York, Newcastle and Berwick Railway, where it is on regular duty."

But the experiment remained unique, even though the locomotive bore out Stephenson & Howe's expectations by hitting 64 mph (103 km/h) while remaining quite steady. Its mechanism proved more complicated than drivers or shop mechanics wanted to deal with. Moreoveer, Zerah Colburn objected that the same result might have been achieved with "a few pounds of counterweight."

Class Plews (Locobase 20103)

Data from John S MacLean "Some Early Locomotive Myths, North Eastern Railway", Locomotive Magazine, Volume 18 (15 April 1912), p. 83.

This design certainly qualified as a "single" as its inside cylinders drove the axle on which 7 foot drivers were mounted. Its colorful scheme used red for the frames (on which the axle journal covers were brass), green for the boiler, drivers and carrying wheels, and splashers, and bright brass for the tall dome.