This was the nickname of the Chicago, Milwaukee, St Paul and Pacific (Milwaukee Road)'s EF-4 and EP-4 class electric locomotives. Together they comprised 12 units built by General Electric as part of a larger 20-unit order for export to the Soviet Union in 1946, and were originally designed to operate on the Soviet Railways (SZhD)'s 3,300 volt DC overhead system.
However, because of deteriorating relations with the Soviet Union, GE did not deliver them. Fourteen were built to the Russian broad gauge (5 ft or 1,524 mm) and the final six were built to standard gauge.
The Milwaukee Road had offered to buy all twenty, plus the spare parts inventory, for $1 million, little more than scrap value—an offer which GE accepted. However, the Milwaukee's Board of Directors would not release the money.
After the start of the Korean War, the Milwaukee needed more locomotives on their electrified mainline, and was also beset by a coal strike which necessitated sending most diesels back East (Milwaukee Lines East steam engines still burned coal, unlike Lines West steamers which were oil-burning). The Board of Directors returned to GE only to discover that eight locomotives and all the spare parts had been sold, and that the price for the remaining twelve locomotives was $1 million. Of the eight sold, three had gone to the Chicago South Shore and South Bend Railroad (the South Shore Line), and five to the Companhia Paulista de Estradas de Ferro of Brazil.
The Milwaukee's railroaders referred to the units as Little Joe Stalin's locomotives which was eventually shortened to simply Little Joe.
The Milwaukee was not impressed with these locomotives to begin with, finding them prone to wheelslip. The WW1-vintage General Electric motor-generator substations had difficulty supplying more than two EF-4s under heavy load and the controls were initially labelled in Russian.
After being given increased weight, and provided with adequate power, the EF-4s were excellent performers and very reliable. Some substations were later modified to supply up to 3,400 Volts to provide more power. Three units used on the South Shore Line were designed for 1500 Volts.
Later modifications to the EF-4s included the removal of driving controls and windows at one end to allow the relocation of some troublesome electrical equipment (improved main circuit breakers) into a cooler environment. (The model for this modification was the EP-4s, in which the Milwaukee workshops replaced the operating controls in the "B" end with a steam generator before they entered service.) The loss of this cab was inconsequential, as many Milwaukee electric locomotives were normally turned at the end of their runs in Avery, Deer Lodge or Harlowton, the road having preferred to maintain only one set of controls even on double-ended units. The most important and final major modification was the provision of multiple unit controls for trailing diesel-electric locomotives. It was not uncommon to see several diesel-electric locomotives being led by, and controlled from, one or two Little Joes or a set of Boxcabs in the 1960s and 1970s (as in the first pic)
The main external difference that distinguished class EP-4 from EF-4 was the use of roller bearings on all axles on the E20 and E21 as delivered. The EF-4s were delivered with roller bearings on the forward (unpowered) trucks only, though they would have individual roller bearing axles substituted piecemeal in the shops whenever an original plain bearing axle on the motorized sets burned out or otherwise failed.
The Little Joes lasted until the end of electric operation on the Milwaukee on 15 June 1974, by which time they were the Milwaukee's only electric road locomotives, all the GE Freight Motors (except two which were used together in multiple unit operation as the Harlowton switcher) having succumbed to old age.
Axle arrangement 2-Do+Do-2
Length: 88 ft 10 in (27.08 metres)
Width: 10 ft 7 in (3.23 metres)
Height: 14 ft 5 in (4.39 metres)
Locomotive weight 545,600 lb (247.5 tonnes)
Weight on drivers: 406,000 lb (184 tonnes)
Traction motors GE750
Top speed 68 mph (109 km/h)
Power output: One hour: 5,530 hp Continuous: 5,110 hp
Tractive effort 75,700 lbf (337 kN)
Locomotive brake Air, 8-EL
(edited from wikipedia)