| After more than 120 years of continuous progress, world
steam locomotive development practically stopped in 1950. Prior to this
time, steam design had seen almost continuous progress ever since the
1830's. The size, power, efficiency, and complexity of steam
locomotives increased. Reliability was improved and servicing
requirements were reduced. Beginning in the late 19th century, the
first challenge to steam rail power appeared in the form of electric
locomotives. However, except in limited areas, electric locomotives
never serious challenged steam mainly due to the high cost of
installing the overhead wires (catenary) to supply power to the
locomotives. In the 1930's, the first serious challenge to steam motive
power appeared in the form of diesel-electric locomotives. Diesels had
first appeared in the 1920's but by the late 1930's, General Motors
"Electromotive" division (EMD) introduced the first diesel-electrics
suitable for mainline passenger trains. Shortly afterwards, the first
practical road freight locomotive appeared in the form of the EMD "FT".
Diesel-electric locomotives had several advantages over steam power,
and steam locomotive builders were slow to recognize that diesel
locomotives were a serious threat to steam supremacy.
What were the advantages of the diesel? Follow this link
for information: Steam vs. Diesel
World War II was both a blessing and a curse for steam
builders. Steam locomotive development was frozen in most countries,
but diesel production was also greatly curtailed. The Pennsylvania
Railroad built its prototype 4-4-4-4 Duplex locomotives and later the
S-1 direct drive steam turbine locomotive. By the end of the war, the
diesel locomotive challenge was perfectly clear, but even at that late
hour, most steam manufacturers were slow to react.
In the U.S., Baldwin was touting it's "Duplex" drive
steam locomotives, which featured two sets of cylinders and running
gear in a rigid frame. However, Baldwin was "hedging its bet" and
simultaneously developing diesel-electric locomotives. ALCO seemed to
have completely abandoned steam development and turned its efforts to
designing mass-produced diesels. Lima was the only U.S. steam builder
which seemed to have any serious interest in new steam. Lima was
developing a new "double Belpaire" boiler which would significantly
improve steam production. The double Belpaire boiler was intended to be
used in conjunction with a new rotary cam, "long compression" poppet
valve system developed by Franklin. Several designs were proposed, but
a new wheel arrangement, the 4-8-6, was promoted highly. Unfortunately,
U.S. railways showed very little interest in advanced steam designs
with minor exceptions. By 1949, commercial steam locomotive production
for domestic usage had ended.
In Europe and elsewhere, motive power production
followed a similar trend. Chapelon and others in France developed
advanced steam locomotives which showed great promise
O.V.S Bulleid's Leader
New engines were built after this time, but following
the lead of the United States, most countries increasingly viewed steam
as being outmoded and obsolete. Diesel locomotives and to a lesser
extent electric locomotives replaced steam around the world.
World steam development reached two distinct pinnacles:
U.S. locomotives were supreme in size and absolute power, and in
mechanical durability. French locomotives, under the guidance of Andre
Chapelon, attained the highest ratings for thermal efficiency, fuel
economy, and power-to-weight ratios. Unfortunately, the excellent
mechanical developments devised in the U.S. and the thermodynamic
developments devised in France saw only limited applications outside of
their respective countries. Other nations contributed many
improvements, but the final steam locomotive developments in the U.S.
and France had the greatest impact on steam locomotive performance.
U.S. locomotives were unmatched for size and brute power
anywhere in the world. Since fuel was cheap (coal or heavy oil) and
trackage was sturdy to support heavy engines, the "brute force" design
philosphy was used. Consequently, the frames, cylinders, axles, and
bearings of these engines were subject to incredible forces. Engines
were required to run long distances without change and the minimization
of routine maintenance was desired. While thermodynamic improvements
were made, emphasis in design was placed on maximum power and
durability.
Up until the 1930's, locomotive frames consisted of
hundreds of parts which had to be machined and hand-fitted to form a
rigid assembly. Cylinders were cast in separate pieces which had to be
machined, bolted together, and precision-fitted to the frames to ensure
a tight fit. In service, bolts would work loose regularly, requiring
almost constant maintenance to maintain the frames and cylinders in
proper alignment. By the 1930's, the Commonwealth Steel Corporation had
perfected steel casting to such a degree that it became possible to
cast the entire frame for a steam locomotive in one piece. This could
include the main frames, cylinders, various brackets, and even air
reservoir cylinders into a single casting. In combination with roller
bearings developed by Timken and SKF, and self-adjusting wedges
developed by Franklin, the cast bed frame greatly reduced running gear
maintenance on modern U.S. steam locomotives.
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