Chicago, Rock Island & Pacific 4-8-2 "Mountain" Locomotives in the USA

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 and for his 22 September 2017 email reporting unlikely boiler pressure values for 177 entries. A Locobase macro caused the error .) 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 and 16" (406 mm) piston valves that were delivered with the two 1914 Rock Island 4-8-2s shown in Locobase 3088. But the later M-50s rolled on taller drivers and compensated by setting the boiler pressure at 200 psi. The last batch (4032-4041) came with 14" (356 mm) piston valves, which set the standard for later engines.

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). 4017-4018, 4020, and 4022-4031 were modified to burn oil and trailed tenders weighing 348,750 lb (158,192 kg) when carrying 20,000 US gallons of water and 5,000 gallons (18,295 litres) of oil.

Some of the later engines were refitted with roller bearings, lightweight main and side rods, and disk-type drivers. See M-50a (Locobase 16415). 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.

Class M-50 (Locobase 3088)

Data from W J Tollerton, "Recent Power for the Rock Island Lines", Railway Age Gazette, Volume 56, No 2 (9 January 2014), pp. 86-88; and "Pacific and Mountain Type Locomotives, CRI&P Ry.", The Railway and engineering review, Volume 54, No. 10 (7 March 1914), pp. 356-359. Works numbers were 54197-54198 in October 1913.

Firebox heating surface included 25 sq ft (2.32 sq m) of arch tubes. Relatively capacious 16" (406 mm) piston valves supplied steam to the cylinders.

These were the first two Mountains on the CRI&P. They were nicknamed the "Gold Dust Twins". 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 Gazette, 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 (50 kph).

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-50a (Locobase 16415)

Data from RI 1 - 1942 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange; and F Wesley Krameck, William D Edson, and Jack W Farrell, Rock Island Steam Power (Potomac, MD: Edson Publications, 2002).

Locobase 201 shows the last 20 M-50s to come on the Rock Island. The 1927 and 1929 locomotives were modernized in 1941-1944 as M-50a with Timken roller bearings on all engine and tender axles, disk-type drivers on the main driver (some engines received additional sets), and Timken lightweight side and main rods.

Another signficant change was the reduction of the cylinder bore to 26", possibly to rebalance the ratio between the cylinder volume and the smaller 14" (356 mm) piston valves delivered with the locomotives.The RISP authors note the drop in tractive effort, but claim the loss "was amply compensated in improved continuous power at high speeds." Boilers used Worthington feed water heaters; 4047-4054 had No 3s on the left side, 4057-4061 used Type S. 4056 had a Coffin type. Multiple throttles improved efficiency. Fifteen used Chambers, five--4052-4056--were equipped with Americans.

RISP's authors describe this refit as "producing a series of outstanding high-speed passenger locomotives." One reason was their smooth ride--stationary tests showed steadiness at 100 mph (161 kph). They add:"Discretion precluded much talk about exceeding speed limits in service, but enginemen suggested that the test bed performance was easily attained--and bettered."

Class MP-49e,f,g/M-50 (Locobase 201)

Data from RI 1 - 1942 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange; and F Wesley Krameck, William D Edson, and Jack W Farrell, Rock Island Steam Power (Potomac, MD: Edson Publications, 2002). (Many thanks to Chris Hohl for his 22 September 2017 email reporting unlikely boiler pressure values for 177 entries. A Locobase macro caused the error. Also, thanks to Chris for his 1 February 2022 email noting this batch's original tender weight and capacities.) Schenectady supplied works numbers 66921-66925 (4042-4046) in June 1926, Brooks delivered 67264-67273 in April 1927, and Schenectady finished off the class with 68032-68033 in September 1929, and 68034-68036 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 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 (7.62 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 both reduced piston valve diameter to 14" (356 mm). All engines used Baker gear except 4043, which is shown in the 1942 diagram as fitted with Walschaert constant-lead radial valve gear.,

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 (118.54 sq m), 46 sq ft (4.27 sq m) less than the later Brooks installation because of 8"(203 mm) shorter tube and flue lengths.

Both batches used Worthington feed water heaters except for the last two Brooks engines, which were fitted with Coffins.

Hand-fired when delivered, this class began receiving Standard BK automatic stokers in 1927. Chris Hohl noted that M50es originally trailed tenders weighing 194,000 lb (87,997 kg) when carrying 10,000 US gallons (37,850 litres) of water and 16 tons (14.5 metric tons) of coal. Locobase found that tenders behind oil-burning M50s 4044-4046 and 4056 carried 5,000 US gallons (18,925 litres) of oil.

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; see Locobase 16415.