Ann Arbor 4-4-2 "Atlantic" Locomotives of the USA

Class Details by Steve Llanso of Sweat House Media

Class I/I-1 (Locobase 7339)

Data fromAA-M&LS 1 - 1928 locomotive diagram book dated supplied in May 2005 by Allen Stanley from his extensive Raildata collection. Works numbers were 43298-43301 in July 1907 and 46202 in June 1909.

These were relatively small Atlantics procured relatively late in that wheel arrangement's short period of ascendancy as a passenger engine. The driver diameter implies local passenger rather than express. The first four were bought in July 1907 and delivered four months later for a total cost of $54,794.46. Adding another two years later required another $14,000.

The diagram notes that 200-201 had the number of tubes and consequently the total heating surface as shown. 202 possessed three fewer tubes for a total EHS of 2,261 sq ft and 203 had 249 tubes and a total EHS of 2,228 sq ft. 204 arrived two years after the first four and had a different tube count - 252 - as well and a total EHS of 2,253 sq ft.

Obviously the class worked out -- possibly because it possessed that very attractive attribute of having been paid for. Unusually, and unlike the identical LS & MS engines procured at the same time (see Locobase 5548), these engines apparently were never superheated.

Two were retired in the 1930s -- 1613 went in December 1933 and 1610 in November 1936. Even in February 1950, the class still averaged 279 miles per day per engine, considerably more than any other class.

The others were scrapped in 1951 at the end of the steam era with 1612 going in January, 1612 in February, and 1614 in March.

Specifications by Steve Llanso of Sweat House Media
Locobase ID7339
RailroadAnn Arbor (AA)
Number in Class5
Road Numbers200-204 / 1610-1614
Number Built5
Valve GearStephenson
Locomotive Length and Weight
Driver Wheelbase (ft)7
Engine Wheelbase (ft)25.96
Ratio of driving wheelbase to overall engine wheebase 0.27
Overall Wheelbase (engine & tender) (ft)58.96
Axle Loading (Maximum Weight per Axle) (lbs)
Weight on Drivers (lbs)91,500
Engine Weight (lbs)161,300
Tender Loaded Weight (lbs)136,000
Total Engine and Tender Weight (lbs)297,300
Tender Water Capacity (gals)6700
Tender Fuel Capacity (oil/coal) (gals/tons)10
Minimum weight of rail (calculated) (lb/yd)76
Geometry Relating to Tractive Effort
Driver Diameter (in)69
Boiler Pressure (psi)200
High Pressure Cylinders (dia x stroke) (in)19" x 26"
Tractive Effort (lbs)23,125
Factor of Adhesion (Weight on Drivers/Tractive Effort) 3.96
Heating Ability
Firebox Area (sq ft)157
Grate Area (sq ft)39.10
Evaporative Heating Surface (sq ft)2286
Superheating Surface (sq ft)
Combined Heating Surface (sq ft)2286
Evaporative Heating Surface/Cylinder Volume267.93
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation7820
Same as above plus superheater percentage7820
Same as above but substitute firebox area for grate area31,400
Power L18278
Power MT398.90


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