Class P (Locobase 7673)

Data from ACL 4 - 1942 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive collection. 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 (The first 10 used Walschaert radial valve gear while the last 5 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 collection.

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-S (Locobase 7681)

Data from ACL 12 - 1954 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive collection. Works numbers were 38240-38245, 38335-38338, 38349-38350 in September 1912.

P-1s were delivered by Baldwin with superheaters and piston valves, thus becoming the first of the line's Pacifics to have that valuable addition. They were passenger engines as opposed to the mixed-traffic 4-6-2s the ACL would soon purchase.

Class P-2 (Locobase 7669)

Data from ACL 12 - 1954 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive collection. 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 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 collection. 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, then carrying it on 69" drivers, Baldwin came up with a successful mixed-traffic Pacific that served throughout the system. Like the P-2s, the P-3s had relatively generous 14"-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 collection. 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 essentially P-3s (Locobase 7670) with more tubes and flues. Baldwin delivered 7 in 1917 and the other 20 in 1918.

Like the earlier ACL Atlantics, this class had relatively generous 14"-diameter piston valves. The last 8 -- 475-482 -- had 18-ft 2-in tubes that reduced heating surface areas slightly. Firebox heating surface included 36 sq ft of combustion chamber and 30 sq ft 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 (Locobase 1417)

Data from 1946 ACL locomotive diagram book supplied in May 2005 by Allen Stanley from his extensive collection.

This was the "light" Pacific design 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)

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 of heating surface.. Almost identical to USRA light Pacific design except for smaller driving wheels and slightly less tube and flue area.

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.