As the diesel locomotive began to emerge as a major force in modern railroad power, the Lima Locomotive Works decided that they had best work on trying to stay relevant. In a study conducted, it was decided that Lima should standardize their locomotive designs as far as they could. What helped at the time was that when it became clear the US may enter the Second World War as an Allied Power, most railroads were faced with the need to flog whatever equipment they had on them to the upmost limit. Many soon realized that this would call for whatever new engines they could get their hands on.
Then, a major game changer came in the form of French designer Andre Chapelon. Having come from his home country early in the Nazi occupation, he saw America as an excellent place to try his hand at applying his ideas. Lima agreed to interviewed him, and were impressed with his ideas for widely using roller bearings, Kylchap exhaust system, enlarged steam passages, enclosed cabs, mechanical stoker or oil burning, and 300 psi boiler. Lima was impressed with many of his ideas, though they did remind him that other than the need to use pre-existing designs for the engines, his ideas would mostly be accepted. Chapelon didn't mind too much, and quickly set to work. In the end, he decided on modeling the engines after various USRA designs. As well as Lima's own designs for the Chesapeake & Ohio. That said, he was able to create relatively new design or two under his rule. Though the restrictions of the time prevented his addition of Belpaire Fireboxes on many engines as he would have liked.
In addition, the idea was that these engines could be fitted with certain kinds of tenders depending on the fuel needs of the railroads. Including 12-wheel ones like those for Western Maryland 2-8-0s and 2-10-0s, and the largest being 16-wheel ones based on the tenders used by the Pennsylvania Railroad R3 4-8-4s and J1 2-10-4s.
MK-F Class 2-8-2s
An HO Scale model of a Western Maryland MK-F, classified as the "N" Class. Admittedly, it's rather inaccurate due to mostly using the toolings of a normal USRA Light Mikado, not to mention the tender not being the WM 12-wheelers.
The first engine to be built was MK-F #001, which was designed off the USRA Mikado with several modifications by Chapelon. Such as roller bearings, Kylchap exhaust system, and mechanical stokers. At first, the engine was tested on various railroads but was not widely accepted. However the engine was eventually tested on the Western Maryland, who almost immediately took a liking to the engine. Eventually ordering 25 of the type for fast freight from Connelsville, PA to Baltimore and classified them as the "N" Class. The success of the MK-F on the "Wild Mary" was eventually recognized by the Norfolk & Western who ordered several of them for use in Ohio on local freight work, referring to them as the "T" Class engines.
BK-F Class 2-8-4s
Nickel Plate #765, today one of the nation's most iconic steam excursion stars, was built as a variant of one of the Lima Wartime BK-Fs.
However, Lima soon saw that most railroads were looking for large engines to haul the war loads. This was especially true in the eastern part of the rail network, where before the largest common engine was the 4-8-2 Mountain type. As was exemplified by the Baltimore & Ohio T-3s, Pennsylvania M1s, and others. However, the War Board demanded that these engines be used primarily for freight. So Lima selected the Nickel Plate S-1 Berkshire as the engine to use for this purpose, and using Chapelon's Exhaust system, built many for all the major Van Seringen roads like NKP, C&O, and the Erie. However, many also went to the Baltimore & Ohio, where they were used to shuttle freight through the Alleghannies and across the Midwest; typically in places to big for engines like the later EM-1 Yellowstones. In addition, a version with Belpaire Fireboxes were built of Canadian National and the Pennsylvania, the former of whom had previously worked with Lima on rebuilding several 2-8-0s into Berkshires in the 1930s.
NT-D Class 4-8-4s
Central of Georgia's NT-Ds were called the K Class of "Big Apples" and were known for the eight-wheeled tenders. The class leader, #451, is today in operational service and is based out of Macon, Georgia.
Eventually, mixed-traffic engines were determined to be planned for possible requests. With the first of these being the NT-D 4-8-4; a mixed-traffic machine designed from the Southern Pacific GS-2s. The first engine to request these was the Central of Georgia Railroad, which had found itself in need of a larger passenger engine. Soon, they could be seen plying all across the Peach State with both freight and passenger trains. These engines were so successful that further examples were ordered by the CofG's parent company Illinois Central for use on their secondary Chicago - New Orleans trains. While another 10 were bought up by the Erie Railroad for their
Erie Limited. However, the use of them as mere mixed-traffic engines meant that railroads further west generally did not see much use for them; not even Southern Pacific saw a need for them to be built.
CS-F Class 2-8-0s and DC-F Class 2-10-0s
Only one USATC S160 stayed in the UK after 1944, and it was never painted in a BR livery. Not that it ever stopped the preservationists.
One of the USATC S250s, which was sent to Poland where it was classified the TyK246. The biggest differences from the original DC-F and original S250s, beyond the bufferbeam and headlight, are designs for the tender and the cab.
Two of the most famous Lima Santadards however would be the CS-F Class 2-8-0 and DC-F Class 2-10-0. These engines were initially built by Lima for use by the Chicago, Indianapolis, & Louisville for fast, heavy freight service on their main line, and were also planned to be ordered by the Louisville & Nashville and Burlington Route. However, the design would eventually explode in fame when the US Army Transportation Corps requested several engines for use as war machines. Eventually classified the S160 and S250, these two engines would find themselves in various nations on the European Continent after the war. As well as running in other nations like China, Korea, and Southern Africa [2].
Other projects
In addition to all these engines, Lima also allowed various railroads to send their steamers to be upgraded with the Kylchap Exhuast System. Eventually virtually all the Pennsylvania Railroad's engines were fitted with this system, as were many of the larger steam engines on the Union Pacific's roster such as the FEF series 4-8-4s and the FSF Hudsons designed from Canadian Pacific Royal Hudsons. The system would eventually be applied again with the Union Pacific's FEF-4 series built jointly between by ALCO and Lima.
[1] Thanks to
@TheMann for letting me use his CN 2-8-4 idea.
[2] ITTL, railroads in Southern Africa are 4ft 8.5 in gauge, as opposed to OTL's 3ft 6in gauge.