This program superheated the A-4 and A-5 Atlantics and created a common class. The differences among the subgroups are minor. All had 4 arch tubes that contribued 24 sq ft to the firebox heating surface.
These relatively low-drivered Atlantics 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 | ||
|---|---|---|
| Class | A-4 / A-5 superheated | A-5 |
| Locobase ID | 6550 | 4131 |
| Railroad | Pere Marquette (PM) | Pere Marquette (PM) |
| Whyte | 4-4-2 | 4-4-2 |
| Road Numbers | 377- | 395-399 |
| Gauge | Std | Std |
| Builder | shops | Brooks |
| Year | 1901 | 1901 |
| Valve Gear | Walschaert | Stephenson |
| Locomotive Length and Weight | ||
| Driver Wheelbase | 6.67' | 6.67' |
| Engine Wheelbase | 27.67' | 26.33' |
| Ratio of driving wheelbase to overall engine wheebase | 0.24 | 0.25 |
| Overall Wheelbase (engine & tender) | 51.35' | |
| Axle Loading (Maximum Weight per Axle) | ||
| Weight on Drivers | 90000 lbs | 83000 lbs |
| Engine Weight | 150000 lbs | 142000 lbs |
| Tender Light Weight | 113260 lbs | 98000 lbs |
| Total Engine and Tender Weight | 263260 lbs | 240000 lbs |
| Tender Water Capacity | 5000 gals | 4500 gals |
| Tender Fuel Capacity (oil/coal) | 10 tons | 10 tons |
| Minimum weight per yard of rail on which locomotive could run | 75 lb rail | 69 lb rail |
| Geometry Relating to Tractive Effort | ||
| Driver Diameter | 72" | 72" |
| Boiler Pressure | 200 psi | 200 psi |
| Cylinders (dia x stroke) | 18" x 26" | 18" x 26" |
| Tractive Effort | 19890 lbs | 19890 lbs |
| Factor of Adhesion (Weight on Drivers/Tractive Effort) | 4.52 | 4.17 |
| Heating Ability | ||
| Firebox Area | 178 sq. ft | 182 sq. ft |
| Grate Area | 41.40 sq. ft | 42.30 sq. ft |
| Evaporative Heating Surface | 1557 | 2074 |
| Superheating Surface | 300 | |
| Combined Heating Surface | 1857 | 2074 |
| Evaporative Heating Surface/Cylinder Volume | 203.33 | 270.84 |
| Computations Relating to Power Output (More Information) | ||
| Robert LeMassena's Power Computation | 8280 | 8460 |
| Same as above plus superheater percentage | 9936 | 8460 |
| Same as above but substitute firebox area for grate area | 42720 | 36400 |
| Power L1 | 16131 | 9352 |
| Power MT | 790.28 | 496.81 |
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