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 16147 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 Wheelbase13.75'13.75'13.75'13.75'13.75'
Engine Wheelbase32.67'32.67'32.67'32.67'32.67'
Ratio of driving wheelbase to overall engine wheebase 0.42 0.42 0.42 0.42 0.42
Overall Wheelbase (engine & tender)65.46'65.46'65.46'65.46'63.92'
Axle Loading (Maximum Weight per Axle)51000 lbs
Weight on Drivers138900 lbs138900 lbs138900 lbs145000 lbs145000 lbs
Engine Weight219500 lbs219500 lbs219500 lbs221300 lbs221300 lbs
Tender Light Weight174350 lbs174350 lbs174350 lbs171250 lbs171250 lbs
Total Engine and Tender Weight393850 lbs393850 lbs393850 lbs392550 lbs392550 lbs
Tender Water Capacity8500 gals8500 gals8500 gals8500 gals9000 gals
Tender Fuel Capacity (oil/coal)14 tons14 tons14 tons14 tons14 tons
Minimum weight of rail (calculated)77 lb/yard77 lb/yard77 lb/yard81 lb/yard81 lb/yard
Geometry Relating to Tractive Effort
Driver Diameter73"73"80"80"80"
Boiler Pressure200 psi200 psi200 psi200 psi200 psi
Cylinders (dia x stroke)22" x 28"22" x 28"22" x 28"22" x 28"22" x 28"
Tractive Effort31559 lbs31559 lbs28798 lbs28798 lbs28798 lbs
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.40 4.40 4.82 5.04 5.04
Heating Ability
Firebox Area230 sq. ft231.70 sq. ft230 sq. ft231.70 sq. ft202 sq. ft
Grate Area54 sq. ft54 sq. ft54 sq. ft54 sq. ft54 sq. ft
Evaporative Heating Surface4078 sq. ft3099 sq. ft4078 sq. ft3099 sq. ft3438 sq. ft
Superheating Surface651 sq. ft651 sq. ft
Combined Heating Surface4078 sq. ft3750 sq. ft4078 sq. ft3750 sq. ft3438 sq. ft
Evaporative Heating Surface/Cylinder Volume331.03251.56331.03251.56279.08
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation1080010800108001080010800
Same as above plus superheater percentage1080012636108001263610800
Same as above but substitute firebox area for grate area4600054218460005421840400
Power L1103271998311317218999628
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 Wheelbase13.33'13.75'13.25'13.75'13.75'
Engine Wheelbase33.33'32.67'34.71'34.71'24.71'
Ratio of driving wheelbase to overall engine wheebase 0.40 0.42 0.38 0.40 0.56
Overall Wheelbase (engine & tender)63.83'65.70'65.94'66.29'66.29'
Axle Loading (Maximum Weight per Axle)48100 lbs49800 lbs
Weight on Drivers138000 lbs146500 lbs146500 lbs154100 lbs149500 lbs
Engine Weight219000 lbs243200 lbs243200 lbs249100 lbs248000 lbs
Tender Light Weight173520 lbs161800 lbs166000 lbs167600 lbs167600 lbs
Total Engine and Tender Weight392520 lbs405000 lbs409200 lbs416700 lbs415600 lbs
Tender Water Capacity9000 gals8250 gals8250 gals8500 gals8500 gals
Tender Fuel Capacity (oil/coal)15 tons12.5 tons14 tons14 tons14 tons
Minimum weight of rail (calculated)77 lb/yard81 lb/yard81 lb/yard86 lb/yard83 lb/yard
Geometry Relating to Tractive Effort
Driver Diameter77"73"73"77"80"
Boiler Pressure200 psi200 psi200 psi200 psi200 psi
Cylinders (dia x stroke)22" x 28"23" x 28"23" x 28"23" x 28"23" x 28"
Tractive Effort29920 lbs34494 lbs34494 lbs32702 lbs31476 lbs
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.61 4.25 4.25 4.71 4.75
Heating Ability
Firebox Area208.70 sq. ft206 sq. ft236 sq. ft202 sq. ft202 sq. ft
Grate Area49.50 sq. ft33 sq. ft49.50 sq. ft49.50 sq. ft49.50 sq. ft
Evaporative Heating Surface2847 sq. ft3927 sq. ft3349 sq. ft4071 sq. ft4071 sq. ft
Superheating Surface651 sq. ft745 sq. ft
Combined Heating Surface3498 sq. ft3927 sq. ft4094 sq. ft4071 sq. ft4071 sq. ft
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 percentage1178166001168299009900
Same as above but substitute firebox area for grate area4967141200556964040040400
Power L120313895820302968610063
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 Wheelbase13.75'13.95'13.33'13.33'
Engine Wheelbase34.71'33.75'35.67'33.33'
Ratio of driving wheelbase to overall engine wheebase 0.40 0.41 0.37 0.40
Overall Wheelbase (engine & tender)66.29'65.46'65.62'62.73'
Axle Loading (Maximum Weight per Axle)52800 lbs
Weight on Drivers154000 lbs149500 lbs163500 lbs135110 lbs
Engine Weight248000 lbs248000 lbs278000 lbs221550 lbs
Tender Light Weight167600 lbs167600 lbs175100 lbs156000 lbs
Total Engine and Tender Weight415600 lbs415600 lbs453100 lbs377550 lbs
Tender Water Capacity8500 gals8500 gals9000 gals9000 gals
Tender Fuel Capacity (oil/coal)14 tons14 tons15 tons10 tons
Minimum weight of rail (calculated)86 lb/yard83 lb/yard91 lb/yard75 lb/yard
Geometry Relating to Tractive Effort
Driver Diameter77"77"77"77"
Boiler Pressure200 psi200 psi200 psi200 psi
Cylinders (dia x stroke)23" x 28"23" x 28"25" x 28"22" x 28"
Tractive Effort32702 lbs32702 lbs38636 lbs29920 lbs
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.71 4.57 4.23 4.52
Heating Ability
Firebox Area232 sq. ft232 sq. ft240 sq. ft174 sq. ft
Grate Area49.50 sq. ft49.50 sq. ft70.40 sq. ft49.50 sq. ft
Evaporative Heating Surface3345 sq. ft3345 sq. ft3951 sq. ft3048 sq. ft
Superheating Surface745 sq. ft745 sq. ft784 sq. ft
Combined Heating Surface4090 sq. ft4090 sq. ft4735 sq. ft3048 sq. ft
Evaporative Heating Surface/Cylinder Volume248.43248.43248.37247.42
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation99009900140809900
Same as above plus superheater percentage1168211682164749900
Same as above but substitute firebox area for grate area54752547525616034800
Power L12136921369196958163
Power MT917.74945.36796.70399.59


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