Maine Central 4-6-4 "Hudson" Locomotives of the USA

The Maine Central Railroad only bought two 4-6-4 Hudsons. This pair (road numbers 701 and 702) was built by the Baldwin Locomotive Works in 1930.

These locomotives had 73" drivers, 23" x 28" cylinders, a 240 psi boiler pressure, a total weight of 312,590 lbs and a tractive effort of 41,300 lbs.

Class Details by Steve Llanso of Sweat House Media

Class D (Locobase 1044)

Data from 1934 Maine Central locomotive tables and MEC-PTC 4 -1956 Locomotive Diagrams supplied by Allen Stanley in May 2005 from his extensive Raildata collection. See also DeGolyer, Volume 81, pp. 67+. (Thanks to Chris Hohl for his 26 February 2016 email adding the booster details.) Works numbers 61370-61371 in May 1930.

Pocket Hudsons, these were the lightest of the wheel arrangement. Their firebox heating surface included 14 sq ft (1.3 sq m) in two arch tubes and 74 sq ft (6.87 m) from two Nicholson thermic syphons. Piston valves measured 12" (306 mm) in diameter and reflected their "long-travel" description by shuttling 9" (229 mm) in each direction. The boiler also included a very high superheater surface area as a percentage of combined heating surface. The Franklin Type C-2-S boosters aided starting tractive effort.

Drury (1993) argues that traffic and economic conditions explain a) why the Maine Central went with Hudsons in the first place, and b) why they only bought two. They served until 1950 (701) and 1955 (702); the last few years of 702 were spent on least to the Portland Terminal Company.

Specifications by Steve Llanso of Sweat House Media
Locobase ID1044
RailroadMaine Central (MEC)
Number in Class2
Road Numbers701-702
Number Built2
Valve GearBaker
Locomotive Length and Weight
Driver Wheelbase (ft)13
Engine Wheelbase (ft)35.67
Ratio of driving wheelbase to overall engine wheebase 0.36
Overall Wheelbase (engine & tender) (ft)72.37
Axle Loading (Maximum Weight per Axle) (lbs)57,600
Weight on Drivers (lbs)171,400
Engine Weight (lbs)312,590
Tender Light Weight (lbs)189,610
Total Engine and Tender Weight (lbs)502,200
Tender Water Capacity (gals)10,000
Tender Fuel Capacity (oil/coal) (gals/tons)14
Minimum weight of rail (calculated) (lb/yd)95
Geometry Relating to Tractive Effort
Driver Diameter (in)73
Boiler Pressure (psi)240
High Pressure Cylinders (dia x stroke) (in)23" x 28"
Tractive Effort (lbs)41,392
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.14
Heating Ability
Firebox Area (sq ft)306
Grate Area (sq ft)62.60
Evaporative Heating Surface (sq ft)3826
Superheating Surface (sq ft)1760
Combined Heating Surface (sq ft)5586
Evaporative Heating Surface/Cylinder Volume284.15
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation15,024
Same as above plus superheater percentage19,832
Same as above but substitute firebox area for grate area96,941
Power L145,967
Power MT1773.74



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