Erie 2-8-8-8-2/4 "Triplex" Locomotives in the USA

Class P-1 (Locobase 3300)

Data from tables in 1930 Locomotive Cyclopedia. See also the original Baldwin specs in DeGolyer, Volume50, pp. 184+ and Volume 55, pp. 125+. Works numbers were 41308 in August 1914 and 43350-43351 in May 1916. (Thanks to Chris Hohl for correcting the valve gear ID and to Steve Low for his 15 April 2020 email spotting a road-number error.)

The goal of the design was to put the maximum tractive effort into a helper engine. The result, conceived and patented by Baldwin's George R. Henderson, was a sort-of-Mallet, sort-of-tank articulated locomotive. One prototype was prepared for testing; two more followed not quite two years later.

The Triplex arrangement of three engine sets had the middle, high-pressure cylinders exhausting into equal-size low-pressure ones fore and aft. The front LP set exhausted into the normally placed stack, which maintained a draft over the grate. The rear cylinder exhausted passed through a feedwater heater of 437 sq ft (40.6 sq m) and up a narrow pipe at the rear of the tank. The firebox heating surface included 108 sq ft (10 sq m) of combustion chamber and 88 sq ft (8.15 sq m) of arch tubes.

Unfortunately for such grand ambitions, the design failed in two important respects:1) it could never have generated sufficient steam as both the boiler and the grate were far too small and 2) the couplers on most freight cars couldn't stand the strain of the prodigious pulling power this design could muster.

As originally delivered, the grate measured 90 sq ft, which gave an impossible GDF of 123,379. The grate seen in the data (122 sq ft) was fitted in the second and third examples. To create the larger grate, the Gaines brick wall in the firebox was removed and the arch tube layout reduced heating surface from 88 to 74 sq ft. (See Wiener, 1930, for comparison data.) As can be seen, however, both demand factors are still far too high.

Comstock (1971) quotes an Erie fireman, Andrew Goobeck, who wrote in an October 1942 Railroad Magazine article that "We used to say that the best place for anybody to cool off on a summer day was behind the ...firedoor." Drury (1993) notes that the engines were never simpled, even for starting, because "two or three revolutions of the drivers would have exhausted the boiler."

Also, although the Matt Shay (first of the three) did start a train of 250 coal cars, the run lasted only 17 miles before the force of the pull snatched one from a coal car and stopped the train. They could be useful pushers, however, and operated on such grades as Susquehanna Hill until the late 1920s.

For Baldwin's Centipede proposal to the Denver & Rio Grande Western prepared in the same year as the Matt Shay's first runs, see Locobase 6823.