The design was of average size and power for its time and represented a substantial increase in power at speed over the M class (Locobase 7668) that had brought the Mikado arrangement to the ACL. The boiler wasn't much bigger, but the grate was substantially ...well ...greater in size. Also, the piston valves diameter increased by 50% to 12" (still not comparable to many other Mikados). In addition, cutting down the tube length by 3 1/2 feet made room for a combustion chamber that contributed 86 sq ft of direct heating surface to the 35 sq ft of arch tubes and the 231 sq ft of the firebox itself.
At the beginning, the locomotives were used in perishable-freight service at relatively high speeds. Drury (1993) says this class served the coal traffic on the Montgomery line until the end of steam in 1952.
The first of a small holding of Mikados on the ACL, these came relatively early in the type's history. As such, they had the low drivers and small grate that signified 2-8-2s that had been derived from earlier Consolidation designs. Also, the 8" piston valves seem positively puny. Still, the ACL found uses for the class, which wasn't scrapped until 1951-1952.
| Specifications | ||
|---|---|---|
| Class | M-2 | M-S |
| Locobase ID | 7667 | 7668 |
| Railroad | Atlantic Coast Line (ACL) | Atlantic Coast Line (ACL) |
| Whyte | 2-8-2 | 2-8-2 |
| Road Numbers | 820-836 | 800-819 |
| Gauge | Std | Std |
| Builder | Baldwin | Baldwin |
| Year | 1918 | 1911 |
| Valve Gear | Walschaert | Walschaert |
| Locomotive Length and Weight | ||
| Driver Wheelbase | 16.75' | 15.75' |
| Engine Wheelbase | 35' | 33.08' |
| Ratio of driving wheelbase to overall engine wheebase | 0.48 | 0.48 |
| Overall Wheelbase (engine & tender) | 70.70' | 67.65' |
| Axle Loading (Maximum Weight per Axle) | 58120 lbs | 48600 lbs |
| Weight on Drivers | 232430 lbs | 183600 lbs |
| Engine Weight | 295030 lbs | 242300 lbs |
| Tender Light Weight | 188000 lbs | 159800 lbs |
| Total Engine and Tender Weight | 483030 lbs | 402100 lbs |
| Tender Water Capacity | 10000 gals | 8000 gals |
| Tender Fuel Capacity (oil/coal) | 14 tons | 15 tons |
| Minimum weight per yard of rail on which locomotive could run | 96.85 lb rail | 76.50 lb rail |
| Geometry Relating to Tractive Effort | ||
| Driver Diameter | 64" | 56.50" |
| Boiler Pressure | 200 psi | 200 psi |
| Cylinders (dia x stroke) | 27" x 30" | 22" x 30" |
| Tractive Effort | 58092 lbs | 43688 lbs |
| Factor of Adhesion (Weight on Drivers/Tractive Effort) | 4.00 | 4.20 |
| Heating Ability | ||
| Firebox Area | 352 sq. ft | 220 sq. ft |
| Grate Area | 73 sq. ft | 54 sq. ft |
| Evaporative Heating Surface | 3306 | 3123 |
| Superheating Surface | 742 | 737 |
| Combined Heating Surface | 4048 | 3860 |
| Evaporative Heating Surface/Cylinder Volume | 166.29 | 236.61 |
| Computations Relating to Power Output (More Information) | ||
| Robert LeMassena's Power Computation | 14600 | 10800 |
| Same as above plus superheater percentage | 17276.19 | 12862.07 |
| Same as above but substitute firebox area for grate area | 83304.35 | 52401.04 |
| Power L1 | 12602.30 | 15490.10 |
| Power MT | 478.14 | 744.00 |
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