Class I (Locobase 6082)

Data from the 1926 Alabama & Vicksburg locomotive diagram book supplied in March 2004 by Allen Stanley from his extensive collection. See also DeGolyer, Vol 59, pp. 68+.

Small Mikados for both the A & V and Vicksburg, Shreveport & Pacific. The A & V locomotives were produced over a long run. 460 (BLW #51644) in March 1919, 461 (55487) in June 1922, and 462-463 (58017-18) in September 1924. The latter two had two more superheater flues and twenty fewer tubes. They also had Nicholson thermic syphons.

The VS & P locomotives were more closely spaced. 360-363 (BLW #42739-42742) were turned out in December 1915. 364 (51675) followed in April 1919, while 365-368 (53059-60 in February and 53091, 53119 in April) finished the class in 1920.

For a detailed description of the Young gear, see Brotherhood of Locomotive Firemen and Enginemen's Magazine, Volume 63, No 7 (July 1917), pp. 52. The biggest difference in the mechanism from the Walschaert gear was the absence of an eccentric on the driver. Instead, the Young used a rock shaft to communicate the movement of a crank arm on one side to the crank arm on the other side.

In response to a question about its configuration and advantages, the BLF replied in part:

"The principal advantages claimed for the Young valve, valve gear and reverse gear, a combination that usually goes together (although the valve gear can be used with any type of valve, or the reverse gear can be used with any type of valve gear), are an improved distribution of steam, and saving all loss from leakage; more effective valve lubrication, resulting in a reduction in friction, and a more accurate valve adjustment for prolonged periods.

It's clear from other commentaries that a big advantage lay in the increased valve travel: "With this type of gear a longer valve travel can be obtained than with either the Walschaert or the Baker, and, on account of the increased valve travel, a greater port opening is possible, thereby allowing for the reduction in the diameter of the valve. In other words, it is claimed that in early cut-offs a Young valve gear, with 11-inch valves, will supply as great a volume of steam to the cylinders as 10-inch valves are capable of with the Walschaert gear."

Impressive. See Locobase 6591 for a report by "4-12-2" on Union Pacific trials that appeared to substantiate the claims.

The BLF respondent concluded his assessment as follows:

"The gear has many good features to commend it, in that it is possible to obtain longer valve travel, as stated before; that all movement is in direct lines, with the wearing parts consisting of pins and bushings; that the valve can be made much lighter, and, owing to the difference in construction, that is, having the packing rings fit into the valve chamber, instead of into the valve itself, the valve rings can always be maintained a much better fit in this way, keeping them always steam tight, doing away with the possibilities of steam leakage, something very hard to control in this day of superheated steam."

All were taken into the Illinois Central and renumbered 3960-3972.