After the Midland Railway had already procured 70 examples of express locomotives in the 4-2-2 wheel arrangement in the late 1880s, the era of express locomotives without a second coupled axle was already considered over. However, the Midland followed the strategy of using smaller locomotives, which were then supported by a second locomotive when required. Then, when steam-powered sanders were introduced, Samuel Waite Johnson developed another single express locomotive.
Inner and outer frames were used to safely transmit the forces of a powerful express locomotive to just one axle. Thus, the driven axle had four bearings and could easily withstand the forces of the internal cylinders. After five examples of the class 115 built in 1896 and 1897, another ten units were built in 1899.
Also in 1899, the class 2601 was presented, of which ten examples were built. The driving wheels were half an inch larger, the boiler pressure was increased from 170 to 180 psi, and the firebox was larger. In addition, the slide valves were replaced with piston valves. Instead of the previous three-axle tender, now a four-axle one was used.
Schematic drawing of class 2601
Die Lokomotive, December 1904
The locomotives were basically used on main routes without significant gradients. There they typically hauled express trains weighing between 200 and 250 long tons and could reach speeds of 90 mph. Some of them were also used in front of trains with 350 long tons and proved their worth there, as long as there were no difficult adhesion conditions. Later, when they could no longer cope with the increased train weights, they were still used as pilot locomotives, sometimes even in front of coal trains. Their service life ended in the late twenties.