Chicago & Alton 4-6-2 "Pacific" Locomotives in the USA

Class I1 (Locobase 9045)

Data from C&A 6-1918 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. See also DeGolyer, Volume 25, p. 207; and "Fast Passenger Power for the Alton", Railway and Locomotive Engineering, Volume 16, No 3 (March 1903), pp. 117, 120-121 and "Chicago & Alton 'Pacific' Locomotive" Railway Age, Volume 35, No 8 (20 February 1903), p. 255-257. (Thanks to Chris Hohl for his 31 March 2018 email supplying the R&LE cite and for noting the original adhesion weight, tender capacities, and boiler pressure.) Works number for this single locomotive was 21476, produced in January 1903

This was an early Pacific--the first built by Baldwin for the standard gauge, Railway Age noted. The Alton used it in trials of comparing the arrangement with 2-6-2 Prairies from neighboring lines. Test runs on Alton track indicated that the Illinois Central 1601 and Lake Shore & Michigan Southern 650 offered the best baselines. Although the tests indicated the Prairie's speed potential, their single-axle leading truck lead to "nosing" at high speeds.

The pair nicely illustrate the difference between an Atlantic (4-4-2) and a Pacific as well. Locobase 4096 shows the 1901 E-1 4-4-2s. Compared to that set of Atlantics, the I-1 had a nearly identical firebox, cylinders only 2" (50.8 mm) greater in diameter (and supplied through similar 12" (305 mm) piston valves). But its tubes were four feet (1,219 mm) longer (and their number increased by about two dozen), and the engines added an extra axle of adhesion. Firebox heating surface included 28 sq ft (2.6 sq m) of arch tubes. Although the original tender carried 9 tons of coal and 8,400 US gallons of water, the Alton later used the larger one shown in the specs.

The 600 was rated to "pull passenger", hauling twelve-car trains of 675 tons to Chicago at an average speed of 46 mph (74 km/h). Only the 600 was fitted with a Player Traction Increaser, which used steam cylinders to transfer some of the weight from both front and rear carrying trucks to the drivers for better adhesion.

For purposes of comparison, Baldwin built a sister that had 80"drivers; see Locobase 16147.

This same locomotive would be superheated; see Locobase 9046.

Class I1 - superheated / P-10 (Locobase 9046)

Data from C&A 6-1918 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. Note: all of the C & A diagrams for superheated Pacifics with 28-element superheaters show 851-sq ft superheater areas. Locobase has adjusted that number to 651 sq ft as it fits not just other 28-element superheater measurements but also is in line with the 745 sq ft of the 32-element superheaters in the I-4s.

Both early Pacifics underwent a superheating makeover that confined itself to redoing the boiler; this entry refers to the 73" diameter variant. The usual subtraction from the total tube number in favor of flues occurred, but was accompanied by an unusual reduction in tube diameter at the same time. The firebox now showed 29.7 sq ft (2.76 sq m) of arch tubes as contributing to firebox heating surface. The engine still had its 12" (305 mm) piston valves.

The makeover kept the locomotive in service for more than a decade and a half before it was retired in September 1938.

Class I2 (Locobase 16147)

Data from C&A 6-1918 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. See also DeGolyer, Volume 25, p. 207; and "Fast Passenger Power for the Alton", Railway and Locomotive Engineering, Volume 16, No 3 (March 1903), pp. 117, 120-121; and "Chicago & Alton 'Pacific' Locomotive" Railway Age, Volume 35, No 8 (20 February 1903), p. 255-257. (Thanks to Chris Hohl for his 6 March 2018 email noting the original boiler pressure, and tender capacity as well as the adhesion weight as delivered.) Works number for this single locomotive was 21487 in January 1903.

As noted in Locobase 9045, Baldwin built two Pacifics to the same order except for a difference in driver diameter. Both had fireboxes that included 17 sq ft (1.58 sq m) of firebrick tubes, 12" (305 mm) piston valves, and an indirect motion because the transmission bar was "arched over the leading driving axle". Like the 600, the 601 originally trailed a tender with 8,400 US gallons (31,794 litres) of water and 9 tons (8.2 metric tons) of coal and boiler pressure was set to 220 psi (15.17 bar).

The 600 rolled on 73" drivers while the 601 used 80" wheels to allow service tests to show which tradeoff worked better for the C&A: a higher tractive effort but potentially lower maximum speed with the 600 or a higher maximum speed at the expense of lower starting tractive effort in the 601.

The RLE article compares the total tube heating surface area as equal to "an area represented by about 61 1/2 ft [18.75 m] length of a country road which measures 1 chain of 66 ft [20.12 m] wide." While praiseworthy for its novelty, the analogy compares apples to kiwis because it includes the firebox heating surface area. To retrospectively hone the analogy, Locobase uses the same comparison for tube area only, where the tube heating surface area equalled 58 ft 1 1/2 in (17.72 m) of country road.

Locobase later realized that the R&LE could have compared the total length of the tubes to a country road. He found that the 328 tubes, each 20 ft long, added up to 6,560 ft or 1.24 statute miles, 1.08 nautical miles, or 1,999.48 metres (i.e. 19" short of 2 km).

Another novelty of this locomotive was its adhesion weight, which was lower than Baldwin's estimate of 144,000 lb (65,317 kg). The Philadelphia builder's weight estimates were usually on the low side.

This same locomotive was later rebuilt with 50 fewer boiler tubes (Locobase 9045) and still later superheated (Locobase 9046).

Class I2 - superheated / P-11 (Locobase 9048)

Data from C&A 6-1918 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. Note: all of the C & A diagrams for superheated Pacifics with 28-element superheaters show 851-sq ft superheater areas. Locobase has adjusted that number to 651 sq ft as it fits not just other 28-element superheater measurements but also is in line with the 745 sq ft of the 32-element superheaters in the I-4s.

Although the saturated version of this design was quite different from the I-1 (Locobase 9045), the superheated conversion resulted in a locomotive whose only differences were the taller drivers and a greater adhesion weight.

Like the 600, the 601 was withdrawn in September 1938.

Class I2- rebuilt (Locobase 9047)

Data from C&A 6-1918 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. See also DeGolyer, Volume 25, p. 207; and "Fast Passenger Power for the Alton", Railway and Locomotive Engineering, Volume 16, No 3 (March 1903), pp. 117, 120-121.

In the same month that Baldwin built the 73"-drivered I-1 (Locobase 9045), it also produced this express passenger version. The boiler and grate remained the same size, as did the cylinders (with their 12"/305 mm piston valves).

At some point, the I-2's boiler shed 50 of its tubes, which reduced heating surface area. Lacking direct comments from sources, Locobase observes that even with the reduction, the vessel still had plenty of area for the cylinder volume, particularly as the taller drivers would have demanded less steam per mile at the same speed. In exchange, the boiler may have gained in ease of water circulation.

The I-2 was superheated; see Locobase 9048.

NB: Thanks to Gunnar Henrioulle, who wrote to Locobase in July 2012, Locobase determined that the original 4-4-2 entry found in Locobase 4790 was based on inaccurate information. The article "The Modern High Speed Passenger Locomotive", Scientific American - New York, Vol XCII, No 20 (20 May 1905), p 402, reported these data, but described the locomotive as an Atlantic (4-4-2). This put the adhesion weight on two axles, which resulted in a much-too-high axle loading.

Class I3 - superheated / P-12 (Locobase 9049)

Data from C&A 6-1918 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. Note: all of the C & A diagrams for superheated Pacifics with 28-element superheaters show 851 sq ft (79.06 sq m) superheater areas. Locobase has adjusted that number to 651 sq ft as it fits not just other 28-element superheater measurements but also is in line with the 745 sq ft (69.21 sq m) of the 32-element superheaters in the I-4s.

In superheating the Harriman Pacifics (Locobase 5313), the Alton installed its standard 28-element superheater assembly that included a reduction in tube count as well as individual tube diameter. Because the Harriman's had smaller boilers to begin with, the result was a high degree of superheat that undoubtedly increased their power.

Class I4 (Locobase 4199)

Oddly proportioned Pacific profiled in the "Pacific Locomotives for the Chicago & Alton", Railroad Age Gazette, Volume 45, No. 18 (2 October 1908), pp. 1041-1042. See also "Pacific Type Locomotives, Chicago & Alton RR", Railway and Engineering Review, Volume 48 (29 August 1908), pp. 702-703; and DeGolyer, Volume 32, p.259. Works numbers were 32875-32876, 32884 in July 1908; 32897-32898 in August.

The grate seems much too small for the boiler, although the relatively small cylinders kept the grate demand factor reasonable. An article in the October 1908 American Engineer & Railroad Journal comments that "has the largest ratio ...of heating surface to grate area in our records." The R&ER report notes that the wagon-top boiler had a narrow firebox, too, but doesn't comment on the unusually high HS/GA ratio.

It's odd that the adoption of the Pacific layout didn't lead to a wider grate. (Drury - 1993 - comments on the narrow firebox, but ascribes 22"cylinders to this batch, which the RAG clearly shows had 23" pistons.) Piston valve diameters were a sizable 16" (406 mm).

RAG's equivocal prediction was"...these are high-powered machines for passenger service, and as the design has been worked out in light of experience with locomotives built some time ago, the performance should be satisfactory."

Locobase 9050 shows the results of superheating this quintet.

Class I4A - small grate / P-13 (Locobase 9050)

Data from C&A 12-1924 and 1 - 1930Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange.

The superheated I-4 Pacifics retained the narrow firebox they had when originally delivered as saturated-steam engines. A later update would remove the boiler with the small grate and replace it with the one used by the I-5 engines. Even in 1930, however, two of the five -- 605 & 609 -- would still be using the narrow grate.

Except for the 5270 (ex-605), which for some reason was retired in August 1933, the I-4s carried on through World War II before being scrapped in October 1946 (5271), January 1947 (5272-5273), and March 1947 (5274).

Class I5 - 80" drivers (Locobase 9052)

Data from C&A 6-1918 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange.

These were the first five locomotives of a fifteen-engine order from Brooks. They had the tallest drivers of any Alton class, 14" (356 mm} piston valves, and the Harriman-Pacific size grate.

See Locobase 9051 for the 77"-drivered variant.and for Locobase 9054 for the superheated variant.

Class I5A - 77" / P-15 (Locobase 9053)

Data from C&A 1 - 1930 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange.

The two sub-variants of the I-5 class went into service as saturated steam locomotives; see Locobases 9051-9052.

When the Alton's 4-6-2s were superheated, the I-5s remained divided into two subgroups based on driver diameter. The five shown in Locobase 9054 had 80" (2,032 mm) drivers, but were otherwise identical except for a 5,500-lb difference in adhesion weight in favor of the 77"-driver engines shown here.

This class had some free-steaming qualities inherent in a relatively large boiler and 14" (356 mm) piston valves, but the Harriman Standard grate area may have prevented a full exploitation of a decent amount of superheat.

5282 was scrapped in September 1938. The other nine remained in service throughout World War II before being withdrawn and scrapped in 1947-1950.

Class I5A - 77" drivers (Locobase 9051)

Data from C&A 6-1918 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. Works numbers were 48904-48913 in August 1910.

After taking delivery of a quintet of Pacifics rolling on 80" (2,032 mm) drivers, this set of ten repeated the dimensions, 14" (356 mm) piston valves, and the Harriman-Pacific size grate. The only substantial change was the 3" (76.2 mm) smaller drivers, which raised the calculated tractive effort proportionally.

See Locobase 9054 for the superheated update.

Class I5A - 80" / P-14 (Locobase 9054)

Data from C&A 1 - 1930 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange.

See Locobase 9053 for comments on the superheating of this HCS design. This HCS set used 3" (76.2 mm) taller drivers, the installment of which required a slightly longer adhesion wheelbase. Otherwise, the two updates were identical.

5277 and 5279 went to the scrapper in February 1938. The other three evaded the ferro-knacker until the late 1940s.

Class I6 / P-16 (Locobase 7584)

Data from reproduction of 1913 Alco Bulletin 1016 on Richard Leonard's [] (accessed 16 June 2006). See also George Drury, Guide to North American Steam Locomotives-revised edition (Waukesha, WI: Kalmbach Publishng, 1915), p. 112.Works numbers were 53339-53348 in April 1913.

These Harriman Pacifics were the equivalent of the Southern Pacific's P-6 class. Drury (1993) noted the tapered boiler course that joined the extended smokebox to the front course. Firebox heating surface area included 32 sq ft (2.97 sq m) from arch tubes. Although they were delivered as long ago as 1913, this decade of locomotives was the last new passenger power the Alton would buy.

Drury reported that a 1943-1944 upgrade included a new superheater, Nicholson thermic syphons, and Worthington feedwater heaters.

Class P (Harriman)/I3 (Locobase 5313)

Data from DeGolyer, Volume 26, pp. 280-281 and the negative caption found at []. . See also "Standard Harriman Pacific Locomotive", American Engineer & Locomotive Journal, Volume 80 , No 3 (March 1906), p. 104. (Thanks to Chris Hohl for his 21 November 2015 email pointing out the tender water capacity), Works numbers were 23681, 23745, 23756 in February 1904.

Baldwin appears to have taken the firebox of the E-1 Atlantic that immediately preceded it and attached to it a longer boiler less densely packed with tubes. At the same time, cylinder diameter grew by two inches (50.8 mm). The result was a design that put 30,000 more lb (13,608 kg) on the drivers.

Drury (1993) says these were Harriman Pacifics and they do have the standard grate and the relatively small 12" (305 mm) piston valves. They entered service with Stephenson gear and inside-bearing trailing trucks, but were later fitted with outside Walschaerts valve gear and outside-bearing trucks. The specifications table on the back of Baldwin builder's photo negative #1828 gives 8,400 US gallons (31,794 litres) Baldwin's order book gave the firebox heating surface area as 179 sq ft (16.63 sq m); the Locobase spec reflects an inked change in the Baldwin specs.

They were also superheated; see Locobase 9049.