Pere Marquette 4-4-2 "Atlantic" Locomotives of the USA

Class Details by Steve Llanso of Sweat House Media

Class A-4 / A-5 superheated (Locobase 6550)

Data from 1929 Pere Marquette Locomotive Diagram book supplied in May 2005 by Allen Stanley from his extensive Raildata collection.

This program superheated the A-4 and A-5 Atlantics and created a common class. The differences among the subgroups are minor. All had four arch tubes that contribued 24 sq ft (2.23 sq m) to the firebox heating surface.

Class A-5 (Locobase 4131)

Builder info from B.Rumary, 25 Kingscombe, Gurney Slade, Radstock, BA3 4TH, ENGLAND and Jeremy Lambert as supplied by Allen Stanley in March 2004. Works #3778-3782 in February 1901.

These relatively low-drivered Atlantics were fitted with Belpaire fireboxes; they were part of a larger order delivered by Brooks in 1901.

The class operated in Michigan until the late 1920s-early 1930s. 397 was scrapped first in June 1928, followed by 399 (December 1928), 398 (September 1929). 395-396 lasted another 5 years before facing the torch on 13 April 1934.

Specifications by Steve Llanso of Sweat House Media
ClassA-4 / A-5 superheatedA-5
Locobase ID6550 4131
RailroadPere Marquette (PM)Pere Marquette (PM)
Number in Class175
Road Numbers377-395-399
Number Built5
Valve GearWalschaertStephenson
Locomotive Length and Weight
Driver Wheelbase (ft) 6.67 6.67
Engine Wheelbase (ft)27.6726.33
Ratio of driving wheelbase to overall engine wheebase 0.24 0.25
Overall Wheelbase (engine & tender) (ft)51.35
Axle Loading (Maximum Weight per Axle) (lbs)
Weight on Drivers (lbs)90,00083,000
Engine Weight (lbs)150,000142,000
Tender Loaded Weight (lbs)113,26098,000
Total Engine and Tender Weight (lbs)263,260240,000
Tender Water Capacity (gals)50004500
Tender Fuel Capacity (oil/coal) (gals/tons)1010
Minimum weight of rail (calculated) (lb/yd)7569
Geometry Relating to Tractive Effort
Driver Diameter (in)7272
Boiler Pressure (psi)200200
High Pressure Cylinders (dia x stroke) (in)18" x 26"18" x 26"
Tractive Effort (lbs)19,89019,890
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.52 4.17
Heating Ability
Firebox Area (sq ft)178182
Grate Area (sq ft)41.4042.30
Evaporative Heating Surface (sq ft)15572074
Superheating Surface (sq ft)300
Combined Heating Surface (sq ft)18572074
Evaporative Heating Surface/Cylinder Volume203.33270.84
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation82808460
Same as above plus superheater percentage96058460
Same as above but substitute firebox area for grate area41,29636,400
Power L116,1319352
Power MT790.28496.81


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