These were the first two Mountains on the CRI&P. When they went into service between Phillipsburg, Kan and Limon, Col., reported WJ Tollerton, Chief Mechanical Superintendent, in Railway Age (9 January 1914), their increased power allowed the railroad to consolidate the St Louis and Chicago sections of Colorado trains into one. Over the ruling grade of 1% westbound, the 4-8-2s were expected to haul 16-car, 1,000-ton passenger trains, making 10 stops, at an average speed of 31 mph. Although these were successful locomotives, the Rock Island didn't order more Mountains until 1920, at which time they renumbered these two 4000-4001.
Firebox had 3 thermic siphons that contributed 141 sq ft to the firebox heating surface and represented all of the increase over the 1913 batch. Note the high CHS/GA ratio and the high adhesive factor. These oddities must have been acceptable because the updated version (M-50a) retained similar numbers.
The class was built by Schenectady and Brooks. As delivered, the tenders carried 10,000 US gallons of water and 16 tons of coal; loaded tender weight came to 194,000 lb.
Some of the later engines were refitted with roller bearings, lightweight main and side rods, and disk-type drivers. See M-50a (Locobase 201).
Eighteen M-50s modified by Rock Island. Note the lower tractive effort, chiefly because of the smaller cylinders. Still has a high CHS/GA ratio and adhesive factor.
| Specifications | |||
|---|---|---|---|
| Class | M-50 | M-50 | M-50a |
| Locobase ID | 3088 | 200 | 201 |
| Railroad | Rock Island (CRI & P) | Rock Island (CRI & P) | Rock Island (CRI & P) |
| Whyte | 4-8-2 | 4-8-2 | 4-8-2 |
| Road Numbers | 998-999 | 4002-4056 | 4047-4061 |
| Gauge | Std | Std | Std |
| Builder | Alco-Schenectady | Alco | Alco |
| Year | 1913 | 1920 | 1929 |
| Valve Gear | Baker | Walschaert | Walschaert |
| Locomotive Length and Weight | |||
| Driver Wheelbase | 18' | 19.83' | 19.83' |
| Engine Wheelbase | 38.92' | 42.25' | 42.08' |
| Ratio of driving wheelbase to overall engine wheebase | 0.46 | 0.47 | 0.47 |
| Overall Wheelbase (engine & tender) | 70.20' | 88.37' | 87.83' |
| Axle Loading (Maximum Weight per Axle) | |||
| Weight on Drivers | 224000 lbs | 255250 lbs | 253500 lbs |
| Engine Weight | 333000 lbs | 378000 lbs | 378500 lbs |
| Tender Light Weight | 160500 lbs | 352400 lbs | 352400 lbs |
| Total Engine and Tender Weight | 493500 lbs | 730400 lbs | 730900 lbs |
| Tender Water Capacity | 8500 gals | 20000 gals | 20000 gals |
| Tender Fuel Capacity (oil/coal) | 14 tons | 20 tons | 20 tons |
| Minimum weight per yard of rail on which locomotive could run | 93.33 lb rail | 106.35 lb rail | 105.62 lb rail |
| Geometry Relating to Tractive Effort | |||
| Driver Diameter | 69" | 74" | 74" |
| Boiler Pressure | 188.50 psi | 200 psi | 220 psi |
| Cylinders (dia x stroke) | 28" x 28" | 28" x 28" | 26" x 28" |
| Tractive Effort | 50975 lbs | 50430 lbs | 47832 lbs |
| Factor of Adhesion (Weight on Drivers/Tractive Effort) | 4.39 | 5.06 | 5.30 |
| Heating Ability | |||
| Firebox Area | 312 sq. ft | 406 sq. ft | 368 sq. ft |
| Grate Area | 62.70 sq. ft | 63 sq. ft | 63 sq. ft |
| Evaporative Heating Surface | 4117 | 4437 | 4437 |
| Superheating Surface | 944 | 1327 | 1276 |
| Combined Heating Surface | 5061 | 5764 | 5713 |
| Evaporative Heating Surface/Cylinder Volume | 206.31 | 222.35 | 257.87 |
| Computations Relating to Power Output (More Information) | |||
| Robert LeMassena's Power Computation | 11818.95 | 12600 | 13860 |
| Same as above plus superheater percentage | 14023.47 | 15500.80 | 16955.63 |
| Same as above but substitute firebox area for grate area | 69781.87 | 99894.03 | 99042.44 |
| Power L1 | 15396.46 | 22756.95 | 28008.49 |
| Power MT | 606.13 | 786.22 | 974.33 |
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