The Chicago, Rock Island & Pacific Railroad received two "Mountains" (road
numbers 998 and 999) from the American Locomotive Company in 1913, and became
the third railroad to take delivery of this wheel arrangement. These two oil
burning locomotives had 28 x28 cylinders, 69" drivers, a boiler pressure of
185 psi, a tractive effort of 50,028 lbs and a total weight of 333,100
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
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.
Class M-50 (Locobase 3088)
Data from Railway Age (9 January 1914).
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.
Class M-50 (Locobase 200)
Data from Railway Age, Vol 70, No 8 (25 Feb 1921); see also "Mountain Type Features New Rock Island Power", Railway Mechanical Engineeer, Vol 95, No 3 (March 1921), pp. 148 and RI 1 - 1942 Locomotive Diagrams supplied in May 2005 by Allen Stanley. (Thanks to Chris Hohl for his correct ID of the valve gear.) Works numbers were 62142-62151 in November 1920, 64180-64189 in April 1923, 64637-64646 in August 1923, and 65773-65782 in July 1924.
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).
Class M-50 - 1929/M-50a (Locobase 201)
Data from RI 1 - 1942 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Raildata collection. Schenectady supplied road numbers 4042-4046 in June 1926, Brooks delivered 4047-4056 in April 1927, and Schenectady finished off the class with 4057-4058 in September 1929, and 4059-4061 in October.
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 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.
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.