In order to increase the power of the ten-wheelers for freight train use, the R-1 was developed on the basis of the R class. The biggest limitation of the R was the firebox, which was located between the frames and could not be enlarged any further.

Therefore, the R-1 received a shallower but wider firebox that stood on the frame. This allowed their width to be increased from 40 to 64 inches. Its walls were corrugated to reduce expansion cracks and increase maintenance intervals. Other changes included increasing the cylinder diameter from 20 to 21 inches, a boiler pressure of 200 instead of 190 psi, and piston instead of slide valves.

No. 444 in the year 2012

Andrew Filer

Between 1901 and 1908 240 locomotives were built by ALCO in Schenectady and 85 by Baldwin. In the beginning, all locomotives had an inside Stephenson valve gear, but in the final series from 1907, an outside Heusinger valve gear was used.

At least 87 locomotives were later fitted with oil firing. 299 units were superheated around 1926. The heating surface of the firebox was once again significantly enlarged by installing arch pipes and thermosiphons. 

As more powerful locomotives became available, the R-1 was progressively pushed out of main line freight service on branch lines. The first larger numbers were phased out from 1939 and by 1957 the last one had disappeared. Three pieces are still preserved today, two of which are being restored.

The class of the D Chicago & North Western was one of the first Atlantics with a wide firebox. With this arrangement, it was quickly discovered that firing was much easier and that much power could even be delivered with inferior coal. Production consisted of a first variant, of which 77 were built between 1900 and 1907, and another, of which 14 were built in 1908.

The first variant had an inside Stephenson valve gear with valves that were also inside the frame. The last ten of the second variant were built with a Walschaert valve gear and Young rotary valves.

The locomotives pulled trains, usually consisting of ten, sometimes eleven cars. 74 were later retrofitted with a superheater. When the wooden cars were replaced with steel cars and more powerful express locomotives were introduced, the class D was used in commuter and local traffic. Almost all locomotives survived into the late 1930s, 15 even survived into the late 1940s.