Class F1 (Locobase 9894)

Data from 1930ca Milwaukee Road locomotive diagram books supplied in May 2005 by Allen Stanley from his extensive collection.

This 4-6-2 wasn't really a "Pacific". Its trailing axle did not support much of the firebox and the boiler certainly wasn't in the same class as the 20th-Century engines that would bear the name.

Class F3 (Locobase 9890)

Data from 1930 & 1945 Milwaukee Road locomotive diagram books supplied in May 2005 by Allen Stanley from his extensive collection.

The F3s arrived with Walschaert gear and 14"-diameter piston valves, but they retained their saturated boilers for a little while. These high-stepping Pacifics would not remain unaltered for long as the Milwaukee was quick to incorporate the advantages of superheat. See Locobase 2785.

Class F3 (Locobase 2785)

Data from 1930 & 1945 Milwaukee Road locomotive diagram books supplied in May 2005 by Allen Stanley from his extensive collection.

This first large class of Pacifics for the Milwaukee Road were among the first to use the DeVoy lateral-motion trailing truck; see Locobase 9890 for the saturated version.

When superheated, the class surrendered 178 small tubes for 28 large flues, but were otherwise not significantly modified. A few (154, 159, 167, 170, 173, 185) did eventually receive 24"-diameter cylinders.

The balance of the basic design was such that these engines shone in passenger service. Jim Scribbins (in Drury, 1993) comments these engines "were among the best of the road's passenger power. They could run 90 mph when worked to the utmost, and the last of them outlived all the Hudsons." And most saw steam out on the road, the last being retired in 1954.

Three were modified with larger grates; see Locobase 9889.

Class F3-as/F1 (Locobase 9889)

Data from 1930 & 1945 Milwaukee Road locomotive diagram books supplied in May 2005 by Allen Stanley from his extensive collection.

These two engines were modified from the original F3 (Locobase 2785) in several important ways. First, the firebox saw a 20% growth in grate area by widening the firebox (but only a small increase in overall direct heating surface). Second, 9 inches were lopped off the tubes and flues, which reduced overall evaporative heating surface area. Third, two of the three received a Hiawatha-like streamline casing based on the F7's (Locobase 183). The porthole centered in a convex smokebox cover and sported a comb on its upper edge which served as the leading edge of a skyline casing that ran in a straight line over the swell of the boiler to the rear of the cab. The retractable coupler and skirts over the cylinders completed the Art Deco look.

These were placed on the Chippewa Hiawatha which ran from Chicago through Milwaukee and Green Bay to Ontagon, Michigan in the Upper Peninsula.

Class F4 (Locobase 9891)

Data from 1930 & 1945 Milwaukee Road locomotive diagram books supplied in May 2005 by Allen Stanley from his extensive collection.

The F4 repeated the F3 design (Locobase 9890), but rolled it on relatively small drivers that made it more suitable for the more mountainous western sections. The Milwaukee was quick to incorporate the advantages of superheat. See Locobase 2786

Class F4 (Locobase 2786)

Data from 1930 & 1945 Milwaukee Road locomotive diagram books supplied in May 2005 by Allen Stanley from his extensive collection.

OS Nock (RWC IV, pl 38) says these were identical to the F3s (Locobase 2785), except that they had 69" drivers for mountain sections. The tractive effort figure given by Jim Scribbins (in Drury, 1993) bears out that analysis.

Scribbins' roster shows 25 engines, as does his commentary. All the F4s soon were superheated and 6 were rebuilt with the larger 24" cylinders of the F5, which suggests that the boiler and grate dimensions in the basic design were more than ample. Retirements began in 1935 and continued in small numbers to 1954.

Class F5 (Locobase 2787)

Data from 1945 Milwaukee Road locomotive diagram book supplied in May 2005 by Allen Stanley from his extensive collection.

This was the last big group of Pacifics for the Chicago, Milwaukee, St. Paul & Pacific and the first to be built with superheaters already installed. Jim Scribbins (in Drury, 1993) says that although they were delivered using 185 psi in the boiler, most eventually pressed their boilers to 200 psi as shown in the specifications. The Milwaukee's own shops built the first 15 F5s and Brooks supplied 50 more in 1912. Six more F5s were derived from F4s (Locobase 2786) in 1914-1926. A few F5s became F5-bs with the mounting of 69" drivers and developed 43,116 lb of tractive effort.

Like the other Pacifics, retirements began in the mid 1930s, but most endured until well after World War II.

Class F5an/F2 (Locobase 9888)

Data from 1945 Milwaukee Road locomotive diagram book supplied in May 2005 by Allen Stanley from his extensive collection.

The F5s described in Locobase 2787 underwent many upgrades and detail tweaks. Two in particular joined the streamliner parade and are profiled in this entry. The streamlining profile resembled that of the F2 (Locobase 9889), which took its inspiration from the F7 4-6-4s (Locobase 183).

In addition to a higher weight than the other members of the class, changes included reducing the diameter of the cylinders by an inch and a half. The casing over the boiler and the front end shrouded the cylinders and Locobase wonders if cutting the cylinder size was necessary have it present a smooth line. (It wouldn't be the first time in railroading that practicality was sacrificed for vanity.)

The two engines served the Midwest Hiawatha's Manilla, Iowa to Sioux Falls, SD section through World War II. Afterward, the tandem was reclassified F2 and moved to the Wisconsin Valley line where they pulled the Northwest Hiawatha until their retirement in 1950.

Class I-2 - saturated (Locobase 9485)

Data from Angus Sinclair (ed), "Fast Passenger 4-6-2 for the C, M, St P" Railway and Locomotive Engineering, August 1903, p. 494 and from CStPMO 4 - 1900 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive collection.

The article reported that they were specifically designed for fast acceleration away from a station stop and that an average train load was 410 tons.