Milwaukee Road class F6

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**Milwaukee Road class F6**
Power type	Steam

Builder	Baldwin Locomotive Works
Configuration	4-6-4
UIC classification	2'C2'
Gauge	4 ft 8½ in (1435 mm)
Driver size	79 in diameter
Locomotive and tender combined weight	266 tons
Boiler pressure	225 psi
Feedwater heater	Coffin flush in smokebox
Fire grate area	80 ft²
Cylinders	2
Cylinder size	26 in dia x 28 in stroke
Career	Milwaukee Road
Class	F6
Number in class	14
Number	6400 – 6413
Delivered	1929
Retired	1952 – 1954

The Milwaukee Road's class F6 comprised fourteen steam locomotives of the 4-6-4 configuration, commonly nicknamed "Hudson" but known as "Baltic" on the Milwaukee. They would have been the first 4-6-4 tender locomotives in the world were it not for the Milwaukee's financial difficulties which culminated in bankruptcy in 1925. The F6 locomotives were not delivered from their builder, the Baldwin Locomotive Works of Philadelphia, Pennsylvania, until 1929–1930.

In 1931, eight sister locomotives of class F6a were delivered; these differed in few aspects but can be distinguished by the straight running boards of the F6a, in contrast to the stepped running boards of the F6.

1 Technical details
2 Modifications
3 Service
4 Speed record
5 References

[edit] Technical details

The 1925 design was by Milwaukee Road Chief Mechanical Engineer C.H. Bilty, with detail design by the Baldwin Locomotive Works, who actually built them. They represented the best of American locomotive practise at the time, and were given all the latest devices and fittings. A Coffin feedwater heater was fitted, which was the Milwaukee's favorite type; this was installed flush in the extended smokebox, and thus was not at all obvious. Possibly because of this, the boiler lagging was continued over the smokebox, which was not common; most North American locomotives had bare smokeboxes which were graphited, rather than painted. The associated steam-driven centrifugal water pump was located under the cab at the left rear.

Valve gear was of the low-maintenance Baker type, with (of course) power reverse. A front-end throttle was installed, with the distinctive linkage running along the boiler on the engineer's side. A mechanical lubricator, driven from the crosshead on the engineer's side, fed oil to the cylinders, valves, guides and other parts of the running gear. Many of the locomotives were fitted with a speedometer, which was attached to the engineer's side frontmost leading axle.

A single air pump for the locomotive and train air brakes was fitted to the fireman's (left) side, with air tanks under the running boards on both sides. Like all larger North American coal-burning locomotives of the time, an automatic stoker was fitted; the 2-cylinder engine to drive this was under the cab floor on the fireman's side.

[edit] Modifications

Locomotive #6401 received large, "Elephant ear" smoke deflectors in 1936 as an experiment; these were kept for several years, but were not fitted to other locomotives. Later that year a sheet-steel pilot was fitted to it and several other locomotives to replace the boiler-tube pilot installed from new. This featured a swing-up coupler. As well as giving a more attractive, streamlined look, this had a serious safety aspect; a sheet-steel pilot without a protruding coupler was more likely to deflect an obstacle without catching on it in e.g. a grade crossing accident.

[edit] Service

At first the locomotives were used mostly between Chicago and Minneapolis, but later on when the F6a locomotives arrived they served as far west as the beginning of the electrified zone.

[edit] Speed record

On July 20, 1934, Milwaukee Road class F6 Baltic #6402 participated in a test run to prove the feasibility of a high-speed service, which was launched as the Hiawatha service in 1935. The test used a regular service train from Chicago, Illinois to Milwaukee, Wisconsin, train 29. This was redesignated as Second 27 just for that day and given a special, high-speed timing. With a five-car train of 840,000 lb (381,000 kg), #6402 completed the 85 miles (137 km) in 67 minutes and 37 seconds start to stop. The eventual Hiawatha timing was 75 minutes for this journey, and the Hiawatha timing was possibly the fastest scheduled train in the world in the 1930s.

While the ends of the trip were taken at relatively low speeds, the 68.74 miles (111 km) between the Chicago suburb of Mayfair and Lake, Wisconsin was completed in 45 minutes and 53 seconds, an average of 89.89 mph (145 km/h). Times were taken with a stopwatch as each station was passed, and in addition the locomotive was fitted with a speedometer; this recorded the speed on a chart, indicating a maximum of 103.5 mph was reached. The fastest inter-station average speed was 95.6 mph between Oakwood and Lake; British expert Brian Reed showed that the latter half of that was an uphill gradient and thus speeds in the first half must have been significantly higher than the overall average. He stated that:

This must be taken as the first time a U.S. steam loco topped "the hundred".

More recently, British train timer Bryan Benn has taken the gradient profile given in Brian Reed's book and shown that it supports a maximum speed in excess of 101 mph during that portion of the run. He believes this is is the first claim of over 100 mph for a steam locomotive in which the surviving documentation strongly indicates its accuracy, and thus that #6402 was the record holder for steam locomotive speed for at least a short time.