Philadelphia & Reading 4-4-4 "Jubilee" Locomotives in the USA

Class C1-a (Locobase 2810)

Data from "The Reading Type Locomotive," Railway Age Gazette, Volume 58, 23a (9 June 1915), p. 1184 and "A Passenger Locomotive of Unusual Interest", pp. 1193-1197. See also "4-4-4 Express Locomotive, Philadelphia & Reading Ry", Locomotive Magazine, Volume XXI [21] (15 December 1915), pp. 270-271. (Thanks to Chris Hohl for pointing out these two installments, which were the first full-length treatments Locobase had seen and which filled gaping holes in the entry; a later email also noted the lack of a Locobase link to P-7b.)

The RAG's report contains details that underscore just how specialized a design these unusual locomotives were. According to RAG, every effort was made to reduce weight in all the parts of the locomotive that weren't the boiler. Heat-treated steel and "high-grade" materials included Mayariu chromium-nickel steel made up the "main and side rods, driving and engine truck axles, main crosshead guides, piston-rod-extension guides, crosshead centers, pistons and piston rods, valve motion parts, and a number of minor parts" Piston valves measured 13" (336 mm) in diameter.

The Reading engineers used aluminum for a variety of components including main crosshead shoes, crosshead for piston-rod-extension, main steam valves, valve-stem crosshead, hand reversing wheel, cab window frames and smokebox door clips. Even the driving and engine truck axles had hollow cores. According to the account, the resulting engine mounted "a larger boiler than any other passenger locomotive now in service on the Reading, while at the same time the total weight of the locomotive is less than that of some engines of other types now in heavy passenger service."

Britain's Locomotive suggested that a virtue in the unusual wheel arrangement was the ability to carry the wide Wootten firebox on a bogie, thus reducing axle load compared to that borne by the usual single-axle trailing truck. It also offered "a short wheelbase with great flexibility." The front and rear bogies were interchangeable.

Certainly the four-point suspension (different from the typical "milking stool" three-point suspension usually used) contributed to the locomotives' failure as a type. The engines were rebuilt as Atlantics (class P7sa) within a year and renumbered 350-353 (see Locobase 9448) .