Lima Locomotive Works 4-4-4 "Jubilee" Locomotives in the USA

Class Light High-Speed Locomotive (Locobase 16458)

Data from W E Woodard, "Steam Locomotive for Light, High-Speed Passenger Trains", Railway Age, Volume 97, No 13 (29 September 1934), pp. 370-372. (Thanks to Chris Hohl for his 12 November 2020 email confirming his correction of the engine wheelbase from 34 ft 4 in to 36 ft 4 in.)

Having developed superpower locomotives in several new wheel arrangements, Lima's CEO Woodard had mastered the difficult equation resulting in power at speed. He and his staff saw another need and proposed this design to meet it. His engineers established some basic requirements for a lightweight streamlined passenger locomotive to pull 250-ton trains at 90 mph (145 kph). Such an engine needed to be safe to operate, as light as possible as "consistent with good design". The locomotive would need to offer rapid acceleration as well as "smooth running at high speed". It should be available with minimum maintenance cost and should achieve "high sustained power output combined with favorable fuel performance."

So the cylinder and boiler needed to permit sustained horsepower output of 2,200 at all operating speeds over 30 mph (48 kph). Firebox and grate were ample enough for the small cylinders, ensuring that "the grate will be worked at a low and economical rate." For example, a coal rate of 88 lb per square foot (3.71 kg/sq m) would evaporated about 43,000 lb (19,504 kg) of steam in a boiler pressed to 275 psi (18.96 bar).

Poppet valves were to be arranged with "compression and release events timed independently of the admission and and cut-off events." This separation of actions permitted "steam distribution in the cylinders best suited for high-speed operation." Woodard elaborated on the benefits. The valves allowed small cylinder clearances and "very short cut-offs" that would achieve "a substantial saving in steam per horsepower", reducing the demands on the boiler.

Added efficiencies would be achieved by an air preheater (Locobase hadn't ever encountered such a device before.) Exhaust steam would be directed to "bundles of fin tubing placed in the air openings of the ashpan." The goal was to maintain a "uniform air temperature under the grates." Woodard predicted that fuel savings would be matched by a reduction in staybolt and side-sheet maintenance.

Smooth, straightline speed would come from driving two coupled axles on the leading drivers, tandem main and connecting rods to place "all reciprocating and rotating parts ...as close as possible to the plane of the counterweights in the driving wheels."

Locobase can't say exactly why no prototype was ever produced, but it's pretty easy to guess a couple of factors. One was the service for which it was intended, which almost certainly didn't require such a high-end jewel box of a locomotive. Another appeared in Woodard's first two paragraphs: the burgeoning presence of internal-combustion (e.g. diesel-electric) power being devoted to passenger trains. When the Burlington inaugurated its Zephyr runs using lightweight, Budd-built unit trains, it put paid to this 4-4-4.

But at least one railway adopted a 4-4-4 for exactly such operations. See Locobases 113-114 for the Canadian Pacific's F-2 and F-1s. The five F-2s, which came first, drove on the front axle, rolled on 80" drivers, and offered less cylinder volume. The 20 F-1s used smaller drivers, smaller cylinders, and smaller boilers.