Milwaukee Road class A

A postcard depicts the Milwaukee Road class A #2 in 1935.

Type and origin
Power type	Steam
Builder	American Locomotive Company
Serial number	68684, 68685, 68729, 68828
Build date	May 1935 (2), May 1936, April 1937
Total produced	4

Specifications
Configuration	4-4-2
UIC class	2′B1′ h2
Gauge	4 ft 8 ¹⁄₂ in (1,435 mm) standard gauge
Driver diameter	84 in (2,134 mm)
Length	88 ft 8 in (27.03 m)
Adhesive weight	144,500 lb (65,500 kilograms; 65.5 metric tons)
Loco & tender weight	537,000 lb (244,000 kilograms; 244 metric tons)
Fuel type	Oil
Fuel capacity	4,000 US gal (15,000 l; 3,300 imp gal)
Water cap	13,000 US gal (49,000 l; 11,000 imp gal)
Boiler pressure	300 lbf/in² (2.07 MPa)
Heating surface	3,245 sq ft (301.5 m²)
• Firebox	69 sq ft (6.4 m²)
Superheater: • Heating area	1,029 sq ft (95.6 m²)
Cylinders	Two
Cylinder size	19 in × 28 in (483 mm × 711 mm)

Performance figures
Tractive effort	30,685 lbf (136.49 kN)
Factor of adh	4.71

Career
Operators	Milwaukee Road
Class	A
Numbers	1 – 4
Retired	1949–1951
Disposition	All scrapped

The Milwaukee Road Class A was a class of high-speed, streamlined 4-4-2 "Atlantic" type steam locomotives built by the American Locomotive Company in 1935-37 to haul the Milwaukee Road’s Hiawatha express passenger trains. Numbered from #1-#4, they were among the last Atlantic type locomotives built in the United States, and certainly the largest and most powerful. The class were the first locomotives in the world built for daily operation at over 100 mph (160 km/h), and the first class built completely streamlined, bearing their casings their entire lives. Although partially supplanted by the larger F7 "Hudsons" from 1937, they remained in top-flight service until the end. Locomotive #3 was taken out of service in 1949 and cannibalised for spares to keep the other three running until 1951. None survived into preservation.

History

Milwaukee Road class A #1 pauses near Milwaukee in 1951.

Designed for a 6½ hour schedule between Chicago and St. Paul, the class proved capable of handling nine cars on a 6¼ hour schedule. The only change over the years, except bumps and dents in the casing, was the addition of a Mars Light beneath the winged emblem on the nose in 1947.

They hauled the fastest scheduled steam-powered trains in the world. Running at 100 mph or greater was required to keep these schedules; the class A locomotives were designed to cruise at over 100 mph and be able to achieve 120 mph (190 km/h). A run with a dynamometer car behind the locomotive was made on May 15, 1935 by locomotive #2 between Milwaukee and New Lisbon, Wisconsin. Over a 14-mile stretch the speed of 112.5 mph (181.1 km/h) was recorded. This was the fastest authenticated speed reached by a steam locomotive at the time, making #2 the rail speed record holder for steam and the first steam locomotive to top 110 mph (180 km/h). There are reports, without evidence or accurate records, that these locomotives could exceed 120 mph. Such speeds would have placed the class A in contention with the LNER Class A4 and German BR 05 for the crown of fastest steam locomotive until that time, but no records have been unearthed. The successor Milwaukee Road class F7 was even more powerful, with a claimed top speed of 125 mph (201 km/h).

The design was fairly conventional but unusual in some aspects. One goal was reducing reciprocating mass, which could not be completely balanced. This was the reason for the high boiler pressure of 300 psi (2.07 MPa), which allowed smaller pistons. The main rods connected to the first pair of driven wheels rather than the (more conventional) second; again, this reduced the reciprocating mass. The large 84-inch (2.134 m) diameter driving wheels reduced piston speed and made high speed less taxing on the machinery. The streamlined casings were designed to open easily for servicing; the front end had clamshell doors ahead of the smokebox.

Table of locomotive^[1]
Milwaukee Road No.	Alco serial No.	Built	Retired
1	68684	000000001935-05-01-0000May 1935	000000001951-11-01-0000November 1951
2	68685	000000001935-05-01-0000May 1935	000000001951-11-01-0000November 1951
3	68729	000000001936-05-01-0000May 1936	000000001949-09-01-0000September 1949
4	68828	000000001937-04-01-0000April 1937	000000001951-06-01-0000June 1951

References

Benn, Bryan. "Fastest Steam Locomotive". Retrieved 2006-01-09.
Ross, Don. "Chicago Milwaukee St. Paul & Pacific: Class A 4-4-2 Hiawatha Atlantics". Don's Rail Photos. Retrieved 2006-01-09.
Hollingsworth, Brian and Cook, Arthur (2001). The Great Book of Trains. Osceola, Wisconsin: MBI Publishing. ISBN 0-7603-1193-5.
Reed, Brian (1972). Loco Profile 26 - The Hiawathas. Windsor, Berkshire, UK: Profile Publications Ltd.
Edson, William D. (Spring 1977). "Milwaukee Road Locomotives". Railroad History (Boston, Massachusetts: The Railway and Locomotive Historical Society, Inc.) (136): 28–129.

↑ Edson 1977, p. 32.

External links

Media related to Milwaukee Road class A at Wikimedia Commons

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