Based on the success of its first two 4-8-2s (renumbered 4000 and 4001) the "Rock Island" ordered ten "Mountains" (road numbers 4002 through 4011) from ALCO in 1920. These Class M50 coal burning locomotives had 28 x 28 cylinders, 74" drivers, a boiler pressure of 200 psi, a tractive effort of 50,430 lbs and weighed 372,850 pounds.
In 1923, thirty more Class M50 locomotives (road numbers 4012 through 4041) were received from ALCO. This time, there was a mix of thirteen oil burners and seventeen coal burners. This batch was identical to the locomotives delivered in 1920 except that the coal burners weighed 367,850 lbs and the oil burners weighed 366,000 pounds.
Three more batches were received: five (road numbers 4042 through 4046) in 1926, ten (road numbers 4047 through 4056) in 1927 and five (road numbers 4057 through 4061) in 1929. These last twenty were built by ALCO and were similar to the others except for an increase in total weight. Four were oil burners and the balance burned coal.
A major rebuild occurred on numbers 4044 through 4061. These eighteen locomotives, designated as Class M50a, were given roller bearings on all axles and light weight running gear. The cylinder bore was reduced from 28" to 26" in a new cast cylinder and forward frame. The boiler pressure was raised to 220 psi, but with the reduced cylinder diameter there was a reduction in tractive effort, which was made up for in greater sustained steaming. These rebuilds were done in the Silvis Shops between 1940 and 1942.
Seven of the CRI&P's "Mountains" (road numbers 4006, 4007, 4015, 4022, 4023, 4028 & 4031) were sold to the St. Louis Southwestern Railroad in 1941. The balance were retired by 1953.
|Road Numbers||Fuel||Wt. on Drivers||Locomotive Weight|
|4012-4041||Oil/Coal||260,250 lbs||366,000/367,850 lbs|
|4044-4046||Coal||253,500 lbs||378,500 lbs|
|4047||Oil||252,900 lbs||372,600 lbs|
|4048-4051||Coal||258,500 lbs||376,500 lbs|
|4052||Coal||259,250 lbs||375,450 lbs|
|4053-4054||Oil||253,450 lbs||371,600 lbs|
|4055||Coal||257,400 lbs||372,900 lbs|
|4056||Oil||251,500 lbs||369,100 lbs|
|4057-4061||Coal||253,500 lbs||378,500 lbs|
Firebox had three thermic syphons that contributed 116.7 sq ft (10.8 sq m) 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. Also, these engines used the square cylinder dimensions that were delivered with the two 1914 Rock Island 4-8-2s shown in Locobase 3088. These M-50 rolled on taller drivers and compensated by setting the boiler pressure at 200 psi.
The class was built by Schenectady and Brooks. As delivered, the tenders carried 10,000 US gallons of water (37,850 litres) and 16 tons of coal (14,515 kg); loaded tender weight came to 194,000 lb (87,997 kg).
Some of the later engines were refitted with roller bearings, lightweight main and side rods, and disk-type drivers. See M-50a (Locobase 201). Seven were sold to the Cotton Belt in May 1941. Chris Hohl suggested that a new Locobase entry would more properly reflect all of the changes made in the St Louis-Southwestern shops after they took delivery. That entry is found at Locobase 16176.
Firebox heating surface included 25 sq ft of arch tubes.
These were the first two Mountains on the CRI&P. American Vanadium Facts emphasized that the Rock Island had adopted vanadium cast steel frames in 1912 for all of its heavy road power and that over 100 such locomotives had entered service since then.
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.
The Rock's 1921 Mountains (shown in Locobase 200) may have had some maintenance issues in the boiler. Given the changes Alco made in these 1926 engines, one suspects that the use of three thermic syphons was a principal culprit as Alco turned out near-duplicates with significant reductions in a couple of areas. Firebox heating surface area was now augmented by two thermic syphons comprising 82 sq ft (7.6 sq m), one less syphon installation than before. The boiler also gave up twelve small tubes in the Schenectady locomotives and fourteen in the Brooks engines and the builder reduced piston valve diameter to 14" (356 mm).
Locobase notes both batches showed an increase in superheater area from the earlier 1923-1924 M-50s. This may have been achieved by using a higher Birmingham wire gauge tube, a difference Locobase has seen in other designs. Schenectady superheaters were credited with a surface area of 1,276 sq ft (118.5 sq m), 46 sq ft less than the later Brooks installation. Both batches used Worthington feed water heaters except for the last two Brooks engines, which were fitted with Coffins.
The 1927 and 1929 locomotives were modernized in 1939-1940 as M-50a with Timken roller bearings on all engine axles, disk-type drivers, and Timken lightweight side and main rods.
|Principal Dimensions by Steve Llanso of Sweat House Media|
|Class||M-50||M-50||M-50 - 1929/M-50a|
|Railroad||Rock Island (CRI & P)||Rock Island (CRI & P)||Rock Island (CRI & P)|
|Number in Class||40||2||20|
|Locomotive Length and Weight|
|Driver Wheelbase (ft / m)||19.83 / 6.04||18 / 5.49||19.83 / 6.04|
|Engine Wheelbase (ft / m)||42.25 / 12.88||38.92 / 11.86||42.08 / 12.83|
|Ratio of driving wheelbase to overall engine wheebase||0.47||0.46||0.47|
|Overall Wheelbase (engine & tender) (ft / m)||88.37 / 26.94||70.20 / 21.40||87.83 / 26.77|
|Axle Loading (Maximum Weight per Axle) (lbs / kg)|
|Weight on Drivers (lbs / kg)||255,250 / 115,780||224,000 / 101,605||260,250 / 118,048|
|Engine Weight (lbs / kg)||378,000 / 171,458||333,000 / 151,046||375,350 / 170,256|
|Tender Loaded Weight (lbs / kg)||352,400 / 159,846||160,500 / 72,802||352,400 / 159,846|
|Total Engine and Tender Weight (lbs / kg)||730,400 / 331,304||493,500 / 223,848||727,750 / 330,102|
|Tender Water Capacity (gals / ML)||20,000 / 75.76||8500 / 32.20||20,000 / 75.76|
|Tender Fuel Capacity (oil/coal) (gals/tons / ML/MT)||20 / 18.20||14 / 12.70||20 / 18.20|
|Minimum weight of rail (calculated) (lb/yd / kg/m)||106 / 53||93 / 46.50||108 / 54|
|Geometry Relating to Tractive Effort|
|Driver Diameter (in / mm)||74 / 1880||69 / 1753||74 / 1880|
|Boiler Pressure (psi / kPa)||200 / 13.80||188.50 / 13||200 / 13.80|
|High Pressure Cylinders (dia x stroke) (in / mm)||28" x 28" / 711x711||28" x 28" / 711x711||28" x 28" / 711x711|
|Tractive Effort (lbs / kg)||50,430 / 22874.69||50,975 / 23121.90||50,430 / 22874.69|
|Factor of Adhesion (Weight on Drivers/Tractive Effort)||5.06||4.39||5.16|
|Firebox Area (sq ft / m2)||396.70 / 36.85||312 / 29||368 / 34.19|
|Grate Area (sq ft / m2)||63 / 5.85||62.70 / 5.83||63 / 5.85|
|Evaporative Heating Surface (sq ft / m2)||4685 / 435.25||4117 / 382.62||4563 / 423.91|
|Superheating Surface (sq ft / m2)||1196 / 111.11||944 / 87.73||1338 / 124.30|
|Combined Heating Surface (sq ft / m2)||5881 / 546.36||5061 / 470.35||5901 / 548.21|
|Evaporative Heating Surface/Cylinder Volume||234.78||206.31||228.67|
|Computations Relating to Power Output (More Information)|
|Robert LeMassena's Power Computation||12,600||11,819||12,600|
|Same as above plus superheater percentage||15,120||14,065||15,498|
|Same as above but substitute firebox area for grate area||95,208||69,986||90,528|