Atlantic Coast Line 4-6-2 "Pacific" Locomotives in the USA

Class P (Locobase 7673)

Data from ACL 4 - 1942 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange; and DeGolyer, Volume 38, pp. 96+ and 103+. Works numbers were 36866-36869, 36877-36880, 36893-36896, 36960-36962 in September 1911.

These were the first ACL Pacifics and the last to be delivered with saturated boilers and balanced slide valves. Firebox heating surface area included 29 sq ft (2.69 sq m) of "fire brick tubes". Like most of the other ACL Pacifics, the P class had a set of 2" (50.8 mm) diameter combustion tubes laid out six a side under the brick arch. (See Locobase 7681 for the smoke-suppressing purpose of these steam-jet tubes.) When the class came on the road, the boiler's pressure was rated at 200 psi, but its working pressure was 185 psi (12.75 bar). Before long, the class was worked at 200 psi as shown in Locobase's specs.

Tender markings included "Coal Capacity 15 tons, Coal Space 11 tons." Locobase hasn't seen that distinction spelled out before, but supposes the lower number represents the actual cubic capacity of the physical tender and the higher number includes coal heaped up above the upper edge at the beginning of a run.

The right of way emphasized speed over the power with no grade over 0.6% (32 ft per mile) and a maximum curvature a nearly tangent 3 degrees. Rail weight came in at a relatively substantial 85 lb/mile (42.5 kg/km).

The first ten used Walschaert radial valve gear while the last five had Baker gear (by Pilliod). Later ACL 4-6-2s had shorter boiler tubes.

Some were later superheated; see Locobase 7674.

Class P - superheated (Locobase 7674)

Data from ACL 4 - 1942 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange.

When compared to the superheated P-1-S delivered a year later (Locobase 7681), the pressure vessel in the only set of Pacifics it had purchased with saturated boilers (Locobase 7673) was quite a bit larger. As a result, superheating the design actually added overall heating surface area to the boiler. Moreover, unlike many retrofits that took the opportunity of superheating to reduce boiler pressure, the ACL maintained its P-class engines at their original settings. The result was a powerful express passenger engine.

Class P-1 (Locobase 7681)

Data from DeGolyer, Volume 41, p. 236. See also "Question: Has any other method of directing air to the fire, other than through the grates, been tried?", Brotherhood of Locomotive Firemen and Enginemen's Magazine, Volume 44, No 5 (May 1909), p. 661; and a summary of the report on the Committtee on Smoke Prevention of the American Railway Master Mechanics Association Convention, reproduced in Railway and Engineering Review, Volume 53, No 25 (21 June 1913), p. 605.Works numbers were 38240-38245, 38335-38338, 38349-38350 in September 1912.

P-1s were delivered by Baldwin with superheaters, becoming the first of the line's Pacifics to have that valuable addition, and 14" (356 mm) diameter piston valves. The firebox repeated the design used in Baldwin's 2-8-0s shown in Locobase 11169. Arch tubes contributed 29.9 sq ft (2.78 sq m) to the firebox heating surface.

The firebox also had 2" (50.2 mm) "combustion tubes" in the throat sheet and on each side of the firebox under the brick arch. Tests at Altoona showed that steam-jets that delivered 4-6 lb of air per pound (1.8-2.7 kg per kg) of coal fired, "the emission of smoke will be reduced to a very low amount, and that while the brick arch is a benefit, particularly while the locomotive is running, the steam jet combustion tube is of value with or without a brick arch." The report later suggested that steam-jets made most difference when the fire on the grate was imperfectly laid.

Obviously, this finding challenged the earlier response to a query published in the 1909 BFLE Magazine's q&a section, which then aserted that the use of combustion tubes had declined because "[t]oo free a use of combustion tubes cooled the fire, causeing a loss of heat which they were intended to overcome."

They were passenger engines as opposed to the mixed-traffic 4-6-2s the ACL would soon purchase. Although some of the grades briefly pitched up at 6%, maximum main-line curvature was no more than 3 degrees and the rails weighed in at a relatively hefty 85 lb/yard (42.5 kg/metre).

Most of the class was scrapped in November 1939. Only 3 were scrapped after 7 December 1941, the last to go being the class leader 275 in December 1944.

Class P-2 (Locobase 7669)

Data from ACL 12 - 1954 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. See also DeGolyer, Volume 47, pp. 9+; and "Question: Has any other method of directing air to the fire, other than through the grates, been tried?", Brotherhood of Locomotive Firemen and Enginemen's Magazine, Volume 44, No 5 (May 1909), p. 661. (Thanks to Chris Hohl for his 24 July 2023 email reporting the correct original pressure and driver diameter.) Works numbers were 40119-40129 in July 1913.

This was the third class of Pacifics to run on the ACL and the variant designed to work freight trains; as Chris Hohl pointed out, they were delivered with 63" (1,600 mm) drivers. Later refitting with thicker tires increased driver diameter to 64". Likewise according to Hohl, the original boiler pressure setting was 170 psi (probably in the belief superheating allowed for reduced pressures and lower maintenance--the tradeoff did not survive ever-increasing traffic demands.). Another sign of the locomotive's intended service was the use of grates simillar to those fitted to a class of Consolidations.

Relatively small cylinders received superheated steam through 14" (356 mm) piston valves. Baldwin's "new style" balanced throttle and power reverse reduced an engineer's effort. Firebox heating surface area included 29.5 sq ft () in four arch tubes.

Six "combustion tubes" (not to be confused with combustion chambers) piercing each side sheet below the brick arch aimed at supplying more air to the fire.But the 1909 BFLE Magazine's response to the question sourced above said that the use of combustion tubes had declined because "[t]oo free a use of combustion tubes cooled the fire, causeing a loss of heat which they were intended to overcome." (See also Locobase 7681). Apparently the ACL believed in their value, however, as Baldwin supplied a class of Mikados with six tubes per side in 1919.

As with most other such designs, the ACL found them less satisfactory than other arrangements. A good factor of adhesion and a relatively large boiler probably accounted for their surviving to the end of steam.

Class P-3 (Locobase 7670)

Data from ACL 12 - 1954 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. See also DeGolyer, Vol 51, pp. 195+ and Vol 59, pp. 29. Works numbers were

1914

March 41252-41258, 41274-41291

1915

November 42652-42657, 42667-42670

1916

October 44260-44264, 44308-44312

Taking the grate of the P-2 (Locobase 7669) as is, and trimming the boiler tubes and flues by two feet (making room for a combustion chamber whose 34 sq ft (3.16 sq m) contributed to the direct heating surface), reducing the size of the firebox slightly but retaining the 30 sq ft (2.79 sq m) of arch tubes and including , then carrying it on 69" drivers, Baldwin came up with a successful mixed-traffic Pacific that served throughout the system.

The firebox also had five 2" "combustion tubes" in each side of the firebox under the brick arch. (See Locobase 7681 for the smoke-suppressing purpose of these steam-jet tubes.)

Like the P-2s, the P-3s had relatively generous 14" (356 mm)-diameter piston valves.

Except for 416 (November 1947), 451-452 (May 1949), 415 (October 1949) and class leader 411 (which exploded February 1950), the class went to the scrapyards in the early 1950s.

Class P-4 (Locobase 7672)

Data from ACL 12 - 1954 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. See also DeGolyer, Vol 59, pp. 42+. Works numbers were

1917

August 46065, 46111, 46128, 46169; September 46273-46274

1918

January 47730-47731, 47798-47799; February 47864-47865, 47918-47919, 47963; March 48076, 48145; April 48267, 48402; June 48905-48906, 48993, 49074; July 49232-49233, 49302.

P-4s were enlarged P-3s (Locobase 7670) with more tubes and flues, a larger grate, and greater cylinder volume due to a 1" (25.4 mm) increase in diameter. Baldwin delivered seven in 1917 and the other twenty in 1918.

Like the earlier ACL Atlantics, this class had relatively generous 14" (356 mm) diameter piston valves. The last 8 -- 475-482 -- had 18-ft 2-in (5.54 m) tubes that reduced heating surface areas slightly. Firebox heating surface included 36 sq ft (3.35 sq m) of combustion chamber and 30 sq ft (2.8 sq m) of "firebrick tubes".

Like most of the ACL's Pacifics, this class served the railroad for over 3 decades. The first two to be scrapped -- 464 and 471 -- went in October 1949. Disposals continued over the next two-and-a-half years and culminated in a final block of 11 in March 1952.

Class P-5-A (USRA) (Locobase 1417)

Data from 1946 ACL locomotive diagram book supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. Richmond works numbers 59310-59319 in March 1919, 61063-61069 in May. , Brooks delivered its contribution (works numbers 61248-61275) in August 1919, Richmond finished off the order with 62069-62093 in 1920.

This was the "light" Pacific design (Locobase 172) standardized by the government-run USRA created in World War I and built by Baldwin and Alco. Alco-Brooks and Alco-Richmond delivered these to the ACL.

Slightly modified versions were built as the P-5-B, which see.

Class P-5-B (Locobase 448)

Data from DeGolyer, Volume 68, pp. 181+ and Volume 75, pp. 1+. See also ACL 3 - 1946 Locomotive Diagrams supplied in May 2005 by Allen Stanley. (Thanks to Chris Hohl for his 9 January 2022 email noting the original boiler pressure and noting which batches had Baker and which had Walschaert's valve gear .)

Works numbers were:

1922

July 55576-55577

September 55627-55631

October 55754-55756

November 55707-55716

1923

January 56132-56134

March 56292-56304, 56374-56377

April 56378, 56404-56406, 56453

October 57367-57369

November 57425-57428, 57438, 57443-57444, 57492-57506

1924

June 57813-57814, 57843-57849, 58492-58494, 58498

July 57878-57884, 57902-57905

1925

June 58484-58485

July 58516-58527, 58564-58566

August 58576-58583

September 58641-58643

October 58770-58777

November 58819-58823

December 58886-58895

1926

January 58931-58935, 58977-58991

Firebox had combustion chamber contributing 44 sq ft (4.1 sq m) of heating surface and 27 sq ft (2.5 sq m) from four arch tubes. Almost identical to USRA light Pacific design (Locobase 172) except for smaller driving wheels and slightly less tube and flue area. Fourteen-inch (356 mm) piston valves supplied the cylinders with steam.

The first 70 locomotives (1600-1669) produced in 1922-1923 used Baker gear, the remaining 95 (1670-1764) delivered in 1924-1926 had Walschaert's constant-lead radial gear. The Baker engines and the first 20 Walschaert's engines used Ragonnet power reverse gear. The last 75 were fitted with Alco Type E.

165 built by Baldwin in 1922-1926 as dual-service locomotives. J Parker Lamb (in Perfecting the American Steam Locomotive, 2003) says that this dual-purpose use was unique among US Pacific operators. The reason lies with the ACL's type of freight traffic -- typically lightweight agricultural products. Like the New York Central, moreover, much of the ACL consisted of water-level running.

Retired in 1950-1953.