Ann Arbor 4-4-2 "Atlantic" Locomotives in 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 Rail Data Exchange. 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. All had 20 sq ft (1.86 sq m) of arch tubes contributing to the firebox heating surface area.

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. (To see what a superheated version of this design might have looked like, go to Locobase 16386, which describes the very similar 1920 pair of Atlantics delivered to short line Pittsburg & Shawmut in western Pennsylvania.)

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.

Principal Dimensions 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 / m)7 / 2.13
Engine Wheelbase (ft / m)25.96 / 7.91
Ratio of driving wheelbase to overall engine wheebase 0.27
Overall Wheelbase (engine & tender) (ft / m)58.96 / 17.97
Axle Loading (Maximum Weight per Axle) (lbs / kg)
Weight on Drivers (lbs / kg)91,500 / 41,504
Engine Weight (lbs / kg)161,300 / 73,165
Tender Loaded Weight (lbs / kg)136,000 / 61,689
Total Engine and Tender Weight (lbs / kg)297,300 / 134,854
Tender Water Capacity (gals / ML)6700 / 25.38
Tender Fuel Capacity (oil/coal) (gals/tons / ML/MT)10 / 9.10
Minimum weight of rail (calculated) (lb/yd / kg/m)76 / 38
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)69 / 1753
Boiler Pressure (psi / kPa)200 / 13.80
High Pressure Cylinders (dia x stroke) (in / mm)19" x 26" / 483x660
Tractive Effort (lbs / kg)23,125 / 10489.34
Factor of Adhesion (Weight on Drivers/Tractive Effort) 3.96
Heating Ability
Firebox Area (sq ft / m2)157 / 14.59
Grate Area (sq ft / m2)39.10 / 3.63
Evaporative Heating Surface (sq ft / m2)2286 / 212.45
Superheating Surface (sq ft / m2)
Combined Heating Surface (sq ft / m2)2286 / 212.45
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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Wes Barris