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


Class Details by Steve Llanso of Sweat House Media

Class I1 (Locobase 9045)

Data from C&A 6-1918 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Raildata collection. 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. 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--that the Alton conducted trials of 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 4 ft (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.

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 Raildata collection. 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" 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 Raildata collection. 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. . 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" piston valves, and an indirect motion because the transmission bar was "arched over the leading driving axle".

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 comparison is apples to kiwis because it includes the firebox heating surface area. Using the same comparison for tube area only, the tube heating surface area was equivalent ot 58 ft 1 1/2 in (17.72 m) of country road.

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 Raildata collection. 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 Raildata collection. 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 grate remained the same size, as did the cylinders (with their 12"/305 mm piston valves), but the boiler contained 50 fewer tubes.

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 Raildata collection. 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.

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. 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.)

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 Raildata collection.

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, 2 of the 5 -- 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 - 77"" drivers (Locobase 9051)

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

These were the first five locomotives of a 15-engine order from Brooks. They had the tallest drivers of any Alton class, 14" piston valves, and the Harriman-Pacific size grate.

See Locobase 9051 for the 77"-drivered variant.


Class I5 - 80"" drivers (Locobase 9052)

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

These were the first five locomotives of a 15-engine order from Brooks. They had the tallest drivers of any Alton class, 14" piston valves, and the Harriman-Pacific size grate.

See 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 Raildata collection.

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. They 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" piston valves, but the Harriman Standard grate area may have prevented a full exploitation of a decent amount of superheat.


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 Raildata collection.

See Locobase 9053 for comments on the superheating of this HCS design.


Class I6 / P-16 (Locobase 7584)

Data from reproduction of 1913 Alco Bulletin 1016 on Richard Leonard's http://www.railarchive.net/alcopacifics/index.html (accessed 16 June 2006).

These Harriman Pacifics were the equivalent of the Southern Pacific's P-6 class. Drury (1993) notes the tapered boiler course that joined the extended firebox to the front course. Although they were delivered as long ago as 1913, this decade of locomotives was the last new passenger power the Alton would buy. Drury notes 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 http://digitalcollections.smu.edu/cdm/singleitem/collection/rwy/id/2055/rec/258. . 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.

Specifications by Steve Llanso of Sweat House Media
ClassI1I1 - superheated / P-10I2I2 - superheated / P-11I2- rebuilt
Locobase ID9045 9046 16,147 9048 9047
RailroadChicago & Alton (C&A)Chicago & Alton (C&A)Chicago & Alton (C&A)Chicago & Alton (C&A)Chicago & Alton (C&A)
CountryUSAUSAUSAUSAUSA
Whyte4-6-24-6-24-6-24-6-24-6-2
Number in Class11111
Road Numbers600600601601601
GaugeStdStdStdStdStd
Number Built111
BuilderBurnham, Williams & CoC & ABurnham, Williams & CoC & ABurnham, Williams & Co
Year1903192219031922
Valve GearStephensonStephensonStephensonStephensonStephenson
Locomotive Length and Weight
Driver Wheelbase (ft)13.7513.7513.7513.7513.75
Engine Wheelbase (ft)32.6732.6732.6732.6732.67
Ratio of driving wheelbase to overall engine wheebase 0.42 0.42 0.42 0.42 0.42
Overall Wheelbase (engine & tender) (ft)65.4665.4665.4665.4663.92
Axle Loading (Maximum Weight per Axle) (lbs)51,000
Weight on Drivers (lbs)138,900138,900138,900145,000145,000
Engine Weight (lbs)219,500219,500219,500221,300221,300
Tender Loaded Weight (lbs)174,350174,350174,350171,250171,250
Total Engine and Tender Weight (lbs)393,850393,850393,850392,550392,550
Tender Water Capacity (gals)85008500850085009000
Tender Fuel Capacity (oil/coal) (gals/tons)1414141414
Minimum weight of rail (calculated) (lb/yd)7777778181
Geometry Relating to Tractive Effort
Driver Diameter (in)7373808080
Boiler Pressure (psi)200200200200200
High Pressure Cylinders (dia x stroke) (in)22" x 28"22" x 28"22" x 28"22" x 28"22" x 28"
Tractive Effort (lbs)31,55931,55928,79828,79828,798
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.40 4.40 4.82 5.04 5.04
Heating Ability
Firebox Area (sq ft)230231.70230231.70202
Grate Area (sq ft)5454545454
Evaporative Heating Surface (sq ft)40783099407830993438
Superheating Surface (sq ft)651651
Combined Heating Surface (sq ft)40783750407837503438
Evaporative Heating Surface/Cylinder Volume331.03251.56331.03251.56279.08
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation10,80010,80010,80010,80010,800
Same as above plus superheater percentage10,80012,63610,80012,63610,800
Same as above but substitute firebox area for grate area46,00054,21846,00054,21840,400
Power L110,32719,98311,31721,8999628
Power MT491.73951.51538.87998.88439.16

Specifications by Steve Llanso of Sweat House Media
ClassI3 - superheated / P-12I4I4A - small grate / P-13I5 - 77"" driversI5 - 80"" drivers
Locobase ID9049 4199 9050 9051 9052
RailroadChicago & Alton (C&A)Chicago & Alton (C&A)Chicago & Alton (C&A)Chicago & Alton (C&A)Chicago & Alton (C&A)
CountryUSAUSAUSAUSAUSA
Whyte4-6-24-6-24-6-24-6-24-6-2
Number in Class355105
Road Numbers602-604605-609 /5270-5274605-609625-634620-624
GaugeStdStdStdStdStd
Number Built5105
BuilderC&ABurnham, Williams & CoC & AAlco-BrooksAlco-Brooks
Year19201908192019101909
Valve GearWalschaertWalschaertWalschaertWalschaertBaker
Locomotive Length and Weight
Driver Wheelbase (ft)13.3313.7513.2513.7513.75
Engine Wheelbase (ft)33.3332.6734.7134.7124.71
Ratio of driving wheelbase to overall engine wheebase 0.40 0.42 0.38 0.40 0.56
Overall Wheelbase (engine & tender) (ft)63.8365.7065.9466.2966.29
Axle Loading (Maximum Weight per Axle) (lbs)48,10049,800
Weight on Drivers (lbs)138,000146,500146,500154,100149,500
Engine Weight (lbs)219,000243,200243,200249,100248,000
Tender Loaded Weight (lbs)173,520161,800166,000167,600167,600
Total Engine and Tender Weight (lbs)392,520405,000409,200416,700415,600
Tender Water Capacity (gals)90008250825085008500
Tender Fuel Capacity (oil/coal) (gals/tons)1512.50141414
Minimum weight of rail (calculated) (lb/yd)7781818683
Geometry Relating to Tractive Effort
Driver Diameter (in)7773737780
Boiler Pressure (psi)200200200200200
High Pressure Cylinders (dia x stroke) (in)22" x 28"23" x 28"23" x 28"23" x 28"23" x 28"
Tractive Effort (lbs)29,92034,49434,49432,70231,476
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.61 4.25 4.25 4.71 4.75
Heating Ability
Firebox Area (sq ft)208.70206236202202
Grate Area (sq ft)49.503349.5049.5049.50
Evaporative Heating Surface (sq ft)28473927334940714071
Superheating Surface (sq ft)651745
Combined Heating Surface (sq ft)34983927409440714071
Evaporative Heating Surface/Cylinder Volume231.10291.66248.73302.35302.35
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation99006600990099009900
Same as above plus superheater percentage11,781660011,68299009900
Same as above but substitute firebox area for grate area49,67141,20055,69640,40040,400
Power L120,313895820,302968610,063
Power MT973.53404.42916.55415.72445.19

Specifications by Steve Llanso of Sweat House Media
ClassI5A - 77"" / P-15I5A - 80"" / P-14I6 / P-16P (Harriman)/I3
Locobase ID9053 9054 7584 5313
RailroadChicago & Alton (C&A)Chicago & Alton (C&A)Chicago & Alton (C&A)Chicago & Alton (C&A)
CountryUSAUSAUSAUSA
Whyte4-6-24-6-24-6-24-6-2
Number in Class105103
Road Numbers625-634620-624650-659 / 5290-5299602-604 / 5267-5269
GaugeStdStdStdStd
Number Built103
BuilderC & AC & AAlco-BrooksBurnham, Williams & Co
Year1922192219131904
Valve GearWalschaertWalschaertWalschaertStephenson
Locomotive Length and Weight
Driver Wheelbase (ft)13.7513.9513.3313.33
Engine Wheelbase (ft)34.7133.7535.6733.33
Ratio of driving wheelbase to overall engine wheebase 0.40 0.41 0.37 0.40
Overall Wheelbase (engine & tender) (ft)66.2965.4665.6262.73
Axle Loading (Maximum Weight per Axle) (lbs)52,800
Weight on Drivers (lbs)154,000149,500163,500135,110
Engine Weight (lbs)248,000248,000278,000221,550
Tender Loaded Weight (lbs)167,600167,600175,100156,000
Total Engine and Tender Weight (lbs)415,600415,600453,100377,550
Tender Water Capacity (gals)8500850090009000
Tender Fuel Capacity (oil/coal) (gals/tons)14141510
Minimum weight of rail (calculated) (lb/yd)86839175
Geometry Relating to Tractive Effort
Driver Diameter (in)77777777
Boiler Pressure (psi)200200200200
High Pressure Cylinders (dia x stroke) (in)23" x 28"23" x 28"25" x 28"22" x 28"
Tractive Effort (lbs)32,70232,70238,63629,920
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.71 4.57 4.23 4.52
Heating Ability
Firebox Area (sq ft)232232240174
Grate Area (sq ft)49.5049.5070.4049.50
Evaporative Heating Surface (sq ft)3345334539513048
Superheating Surface (sq ft)745745784
Combined Heating Surface (sq ft)4090409047353048
Evaporative Heating Surface/Cylinder Volume248.43248.43248.37247.42
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation9900990014,0809900
Same as above plus superheater percentage11,68211,68216,4749900
Same as above but substitute firebox area for grate area54,75254,75256,16034,800
Power L121,36921,36919,6958163
Power MT917.74945.36796.70399.59


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