The reference for locomotives and railcars


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Chicago, Milwaukee, St. Paul & Pacific (Milwaukee Road) class A
United States | 1935 | 4 produced
No 2, which reached 112.5 mph at the first time with a dynaometer car
No 2, which reached 112.5 mph at the first time with a dynaometer car
Robert Graham / collection Taylor Rush

In order to increase average speeds in the fight against other railroads, the Milwaukee Road had ALCO build four class A streamlined locomotives from 1935 onwards. In order to save weight, not only particularly light passenger cars were developed for the “Hiawatha”. Weight was also saved on the locomotives by choosing the 4-4-2 wheel arrangement, which was no longer used in the USA by this time.

By only having two driving axles, the moving masses could be reduced. Furthermore, the first driving axle was driven, which led to shorter connecting rods. Additionally, a boiler pressure of 300 psi (20.7 bars) was used, allowing smaller cylinders with lighter pistons to be used. Despite only two cylinders and the imperfect mass balancing, high speeds could be achieved with seven-foot drivers.

Shortly after its delivery in May 1935, number two reached a speed of 112.5 mph (181 km/h), which could be counted as a world record thanks to the dynamometer car that was present. There are also unconfirmed reports of speeds in excess of 120 mph. What is undisputed, however, is that they were able to travel at sustained speeds in excess of 100 mph with their light trains.

The 422 miles from Chicago to St. Paul were to be completed in six and a half hours with eleven stops. In fact, the trains completed this route in six and a quarter hours. Even after the introduction of the more powerful class F7 Hudsons, they continued to pull the Hiawatha. Between 1949 and 1951 they were replaced by diesel locomotives.

Axle config4-4-2 (Atlantic) 
Gauge4 ft 8 1/2 in (Standard gauge)
Dimensions and Weights
Wheelbase36 ft 7 in
Fixed wheelbase8 ft 6 in
Total wheelbase79 ft
Service weight286,000 lbs
Adhesive weight142,000 lbs
Total weight505,620 lbs
Axle load71,000 lbs
Water capacity13,000 us gal
Fuel capacity4,000 us gal (oil)
Power sourcesteam
Estimated power3,500 hp (2,610 kW)
Optimal speed73 mph
Top speed110 mph
Starting effort30,685 lbf
Power Plant
Driver diameter84 in
Boiler pressure300 psi
Expansion typesimple
Cylinderstwo, 19 x 28 in
Grate area69 sq ft
Firebox area294 sq ft
Tube heating area2,951 sq ft
Evaporative heating area3,245 sq ft
Superheater area1,029 sq ft
Total heating area4,274 sq ft
Calculated Values
steam locomotive
last changed: 01/2024

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