MILW class A

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MILW class A
Hiawatha streamlined steam locomotive 1951.JPG
Numbering: 1-4
Number: 4th
Manufacturer: ALCO
Year of construction (s): 1935-1937
Retirement: 1949, 1951
Axis formula : 2'B1 'h2
Type : Atlantic
Gauge : 1435 mm ( standard gauge )
Length: 16,200 mm (without tender), 27,020 mm (with tender)
Height: 4,400 mm
Fixed wheelbase: 2,600 mm
Service mass: 131.5 t
Service mass with tender: 252.3 t
Friction mass: 65.4 t
Wheel set mass : 32.7 t
Top speed: > 193 km / h
Indexed performance : > 2,940 kW
Driving wheel diameter: 2,134 mm
Impeller diameter front: 914 mm
Rear wheel diameter: 1,295 mm
Control type : Heusinger
Number of cylinders: 2
Cylinder diameter: 483 mm
Piston stroke: 711 mm
Boiler overpressure: 21 bar
Heating pipe length: 6591 mm
Grate area: 6.40 m²
Superheater area : 95.60 m²
Evaporation heating surface: 301.50 m²
Water supply: 49 m³
Fuel supply: 15 m³ of oil

The steam locomotives of the Class A of the Milwaukee Road were the largest, most powerful and fastest Atlantic - locomotives ( wheel arrangement 2'B1 ') that were ever built. They were among the fastest steam locomotives in the world.

Emergence

Three railroad companies competed for the connection between Chicago and the twin cities Minneapolis and St Paul , the Chicago, Burlington and Quincy Railroad , the Chicago and North Western Railway and the Chicago, Milwaukee, St. Paul and Pacific Railroad, or Milwaukee Road for short. This connection was among the busiest in the United States . The three routes were 694, 674 and 680 kilometers long, so the difference in travel time was not that significant. In the early 1930s, the journey took about 10 hours.

All three railways aimed to accelerate traffic, the superstructure of the lines was improved and new trains were planned. At the end of 1934, Chicago & North Western had some sets of express train cars and twelve Pacific locomotives converted. The locomotives were able to pull the trains at 160 km / h and more for long periods of time, and an average of around 100 km / h was achieved over the entire route. A few months later, the Burlington followed with a diesel - electric express railcar called " Pioneer Zephyr " , which was a little faster and was considered America's fastest train.

The Milwaukee Road now had to counter this competition. It was decided against a railcar and a steam-hauled train; The reasons for this were the greater flexibility in terms of space, the not yet fully developed diesel technology , lower investments and greater safety in the event of a collision at a level crossing .

In the end, two express locomotives were ordered from ALCO , which were designed in close cooperation with the chief engineer of the CH Bilty railway. The train sets for two required 12 four-axle express train - passenger cars built the Milwaukee Road in their own railway workshops. " Hiawatha " was chosen as the name for the new train , after the legendary, nimble-footed Indian chief Hiawatha .

The design and manufacture of the two locomotives took only a few months, and on April 30, 1935, the first machine was presented to the public for the first time in a ceremony. The second followed a few days later. As the flagship horses of Milwaukee Road, they were given track numbers 1 and 2.

technology

The class A was significantly larger than the previously largest and most powerful Atlantics of the class E6s of the Pennsylvania Railroad, built from 1914 , and the permissible axle loads allowed a friction weight of 642 kN (65.5 t). That was more than European Pacific locomotives had and was completely sufficient for the planned train weight of around 320 tons. The absence of a third coupling axle reduced the friction of the engine and, above all, the to-and-fro engine masses. The relatively high pressure of the boiler of 300 psi (20.7 bar) also contributed to this, which enabled the use of relatively small cylinders and pistons , and the drive and coupling rods were made of high-alloy steel , so that weight could also be saved here. Unlike most of the earlier Atlantics, the drive rods worked on the first coupling axle, which was a relatively large distance from the bogie .

Despite the intended high speeds, a three-cylinder engine was not used. This type of engine was very rare in the USA; the main reason for this was the poor accessibility of the inner cylinder and the associated higher maintenance costs.

The vehicles had a continuous cast steel frame with cast cylinders. The bottom of the tender was also a cast steel part. All of the locomotive and tender wheelsets ran in roller bearings .

The streamlined cladding designed by Otto Kuhler with very clear lines by American standards covered almost the entire locomotive. Only the lower half of the large drive wheels could be seen because the lower edge of the fairing was roughly level with the wheel centers.

The locomotives were fired with oil. The five-axle tender could hold 15 m³ of oil and 49 m³ of water, whereby the oil supply was sufficient for the entire intended route. The tender's front bogie was three-axle, the rear two-axle, and its design was similar to that of the express train carriages. The cross-section of the tender also corresponded to that of the attached wagons , so that there was a good visual transition between the locomotive and the wagon train. The transition between the locomotive and the tender did not interrupt the clear lines either.

speed

During the test runs carried out from the beginning of May 1935, the locomotives easily reached the intended speeds. During a test run on May 15, 181 km / h were achieved. Class A was officially the fastest steam locomotive in the world for about a year - until the record run of the German 05 002 on May 11, 1936.

The speed of 181 km / h may have reached the New York Central Railroad's No. 999 as early as 1893 . Unlike this locomotive, the class A was able to maintain this speed in daily operation and for a long time. In practice, the locomotives were even faster. The 120 mph (193 km / h) limit was regularly exceeded, and the unofficial values ​​of up to 130 mph (209 km / h) do not seem completely unrealistic, given the design of the locomotives. If this information is correct, then the class A locomotives are among the fastest steam locomotives ever, alongside the duplex locomotives of the Pennsylvania Railroad (classes S1 and T1 ).

commitment

Scheduled operations began on May 29, 1935. The "Hiawatha" was now the fastest connection between Chicago and Minneapolis-St. Paul. The timetable required speeds of at least 160 km / h on the open line, which the locomotives easily managed in daily use.

The "Hiawatha" was therefore a complete success, and the number of passengers rose. More cars were built, and a third locomotive entered service in 1936 and a fourth in 1937. But the starting difficulties with the increasingly heavy trains increased, so that as early as 1937, only two years after the introduction of the "Hiawatha", larger and more powerful locomotives had to be procured. They were Hudson locomotives (wheel arrangement 2'C2 ', class F7 ). However, despite the drive wheels of the same size, these ran much more restlessly than the Atlantics at high speeds and therefore did not reach their maximum speed.

When the tractive power of class A was no longer sufficient for the main lines, they were used together with their car sets for the "Midwest Hiawatha". But a little later diesel locomotives caught on, and in 1949 the number 3 and in 1951 the remaining three locomotives were retired. All four copies were scrapped. Unlike many other streamlined locomotives, they kept their fairing until the end.

literature

  • Wilhelm Reuter: record locomotives . Motorbuch Verlag, Stuttgart, ISBN 3-87943-582-0
  • CH Bilty: The Hiawatha Story . In: Trains . Kalmbach Publishing Co., December 1950, ISSN  0041-0934 , p. 26-30 .

Web links

Commons : Milwaukee Road class A  - collection of pictures, videos, and audio files