The reference for locomotives and railcars
ALCO HH series
HH600, HH660, HH900 and HH1000
United States | 1932 | 177 produced
Milwaukee Road HH660 No. 983, which now stands in the Illinois Railway Museum
Milwaukee Road HH660 No. 983, which now stands in the Illinois Railway Museum
collection Taylor Rush

The HH series were the first diesel shunting locomotives that ALCO mass-produced in large numbers. They were also among the first land vehicles with a diesel-electric transmission. “HH” stood for “High Hood” while the number stood for the engine power in hp. The first HH600 demonstrator was sold to New Haven after testing in 1931. In 1934, industrial designer Otto Kuhler revised the shape of the locomotive body, giving it more rounded corners.

HH600 No. 913 of the New Haven on a 1938 ALCO advertising brochure
HH600 No. 913 of the New Haven on a 1938 ALCO advertising brochure

The first variant had a McIntosh & Seymour 531 with six cylinders. It wasn't until 1937 that the HH900 followed with a turbocharged variant of this engine. In 1938 the HH660 followed with the slightly more powerful naturally aspirated engine of the 538 series and from 1939 finally the HH1000 with the turbocharged variant of the engine of the 538 series. A total of 177 locomotives were built, of which the HH600 was the most successful with 79 units due to its long production period. The individual railway companies operated a maximum of twelve of each model.

Axle configB-B 
Gauge4 ft 8 1/2 in (Standard gauge)
Dimensions and Weights
Length43 ft 5 in45 ft 2 3/4 in
Wheelbase29 ft 8 in28 ft 2 in30 ft 3 in
Fixed wheelbase8 ft
Service weight206,120 lbs230,000 lbs
Adhesive weight206,120 lbs230,000 lbs
Axle load51,530 lbs57,500 lbs
Power sourcediesel-electric
Top speed40 mph60 mph
Starting effort59,799 lbf69,016 lbf72,388 lbf
EngineMcIntosh & Seymour 531McIntosh & Seymour 538McIntosh & Seymour 531TMcIntosh & Seymour 538T
Engine type6-cyl. diesel
Fuel635 us gal (diesel)
Engine output600 hp (447 kW)660 hp (492 kW)900 hp (671 kW)1,000 hp (746 kW)
Power Plant
Calculated Values
diesel locomotive
last changed: 03/2023

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