Class P-1 - simpled & superheated (Locobase 8514)

Data from CB&Q Assorted Steam Diagrams supplied in May 2005 by Allen Stanley from his extensive collection.

Locobse 369 tells how the 5-engine compound Atlantic class was an immediate success in that configuration. But most railroads were drawn toward simpler operation and superheat before too long and the Burlington followed that trend. In 1914-1915, the class was rebuilt in the West Burlington shops as simple-expansion engines. Soon after that, the boiler was reworked in the usual manner, sacrificing some portion of overall heating surface area in favor of installing a set of superheater elements. One curiosity of the diagram, however, is that the flue diameter is given as 6", as opposed to the usual 5 3/8" or 5 1/2".

Whatever the diameter, the newly recharged P-1s carried on in service for another two decades, only retiring in 1932-1933.

Class P-1-C (Locobase 369)

Data from a locomotive diagram published on Vernon Beck's website -- http://home.earthlink.net/~vnlbeck/A/a2d2.tif (accessed 22 March 2003).

Tractive effort given by railroad as 16,400 lb with 84 1/2" drivers, 17,800 lb with 78" drivers. . These compound locomotives (Baldwin works #16547-16548, 18332-18333, 18337) had the 13 1/2-in high-pressure cylinders over the 23-in low-pressure jugs; both were fed by the same piston valve, which was operated by inside Stephenson link motion.

Corbin & Kerka (1960, p 85-86) report that these engines were immediately satisfactory. 1591 ran almost 16 months (7 April 1899 to 30 July 1900) without general repairs and racked up 160,806 miles. 1592 hauled a 200-ton, 4-car fast mail the 83 miles from Mendota, Wis to Chicago in 77 minutes.

Like many US compounds, these engines were rebuilt to 2-cylinder simple expansion. They received 19" x 26" cylinders in 1914-1915 and were later superheated; see Locobase 8514.

Class P-2 (Locobase 370)

Originally built for the St Louis, Keokuk, and Northwestern in 1903, these express passenger locomotives had a coned boiler, inside piston valves operated by Stephenson link motion, a long leading truck, and extended smokebox. They were simple-expansion brothers to the P-2Cs with the principal additional difference of having 30.2 sq ft of arch tubes contributing to the firebox heating surface.

Additional data from Vernon Beck's hosting of locomtive diagrams -- http://home.earthlink.net/~vnlbeck/P/p2.tif (visited 12 April 2003).

Most of the class ran from 1903 to 1930. Eight were rebuilt as P-6-As.

Class P-2-C (Locobase 4090)

Described in a table in Paul T Warner's article on Atlantics in the Railway & Locomotive Historical Society Bulletin #62 (1943, p 20). Data corrected by a table in AERJ July 1903.

This was a Vauclain compound design with very tall drivers and wide firebox behind the drivers borne by an outside-frame trailing truck. According to Corbin & Kerka's (1960, p 282) tables, all of these were rebuilt as P-5 simple-expansion engines in 1915-1917; see Locobase 5454.

Class P-3 (Locobase 8515)

Data from CB&Q Assorted Steam Diagrams supplied in May 2005 by Allen Stanley from his extensive collection

A year after the 6 balanced-compound P-3-Cs came on the road (Locobase 2898), the Burlington began operating these simple-expansion counterparts from Rogers. Although rated at 210 psi working pressure, this class usually ran at 200. Unlike other Burlington 4-4-2s, this class was not superheated except for the 8 that were converted to P-6-A class in 1927-1928; see Locobase 5455.

Class P-3-C (Locobase 2898)

Balanced compounds delivered with two different driver sizes: 78" on the first 10, 74" on the last 10. Used a divided drive in which the HP cylinders inside drove on the first axle and the LP cylinders drove on the second.

The design had a prominently necked down boiler from the first to the second course and an extended smokebox. Later rebuilt as P-5 simples.

Corbin & Kerka (1960, 89) report that July 1904 tests with the lead engine -- 2700 -- yielded results such as 42.24 mph average over a 143-mile distance (McCook, Neb to Akron, Col pulling a 580-ton train. A continuous run from Creston to Chicago (393 miles) took 9 hours, an average of 43.67 mph. These are impressive performances: Few passenger engines in any country could go so far at a decent average speed pulling so heavy a trailing load.

All of the P-3-Cs were rebuilt as P-5 or P-6 simple-expansion in the mid-1920s. See Locobase 5454 and 5455, respectively.

Additional data from table in July 1904 AERJ. (Slightly different data in a June 1907 table.)

Class P-4 (N-1) (Locobase 5453)

Data from a locomotive diagram published on Vernon Beck's website -- http://home.earthlink.net/~vnlbeck/P/p4.tif (accessed 22 March 2003). This single Atlantic was "entirely rebuilt" according to the 1912 diagram referred to above. I'll say. A comparison of all the major dimensions except the cylinders shows a very different locomotive. This rebuild probably extended the life of the frame and cylinders for another 2 decades until 1929.

Class P-5 (Locobase 5454)

Data from a locomotive diagram published on Vernon Beck's website -- http://home.earthlink.net/~vnlbeck/P/P5.tif (accessed 22 March 2003). These were rebuilds of 6 P-2-Cs -- Locobase 4090 -- in 1915-1917 and 14 P-3-Cs -- Locobase 2898 -- in 1924-1927 Atlantics that added superheating, 12" piston valves. The firebox heating surface included 20.29 sq ft of 3 arch tubes. Note the considerable growth in weight on the drivers.

The Burlington Route seems to have prized its Atlantics, rebuilding them for more service when other railroads simply scrapped them. This class of simpled former compounds lasted into the 1940s. One retired as late as 1953.

Class P-6/P-6A (Locobase 5455)

Data from a locomotive diagram published on Vernon Beck's website -- http://home.earthlink.net/~vnlbeck/P/P6.tif (accessed 22 March 2003). These were rebuilds of 6 P-3 (P-6) and 8 P-2s (P-6A) in 1927-1928 that were very similar to the P-5s updated at the same time, but with even more weight on the drivers. Improvements included superheating, 12" piston valves. The firebox heating surface included 20.29 sq ft of 3 arch tubes. Some of the P-6As were fitted with 69" drivers, which must have improved their traction.

All of them endured in service until the late 1940s with the last leaving the railroad in 1954.