Class P-1 to P-6 (Locobase 4408)

Data from"Report of Committe on Power-Chicago, Rock Island & Pacific Railway-Descriptions of Standard Types of Locomotives," American Engineer and Railroad Journal, Volume 79 ( March 1905), pp. 84-86. See also DeGolyer, Volume 25, pp. 190+; Volume 37, pp. 112+.

Light Harriman Common Standard Pacifics built in significant numbers for the Union Pacific. See 5340 for introduction to the HCS idea and 7263 for the SP, LA & SL (LASL) holding later designated P-1. Works numbers were:

1903

December 23341, 23348, 23360-23362, 23376, 23383, 23395, 23403-23404, 23416-23417, 23431, 23456, 23460

1904

January 23476, 23482, 23491; March 24004

1906

July 28534-28535, 28549-28550, 28593, 28600 in July

1907

April 30744-30745, May 30760-30761

1909

August 33642-33647, 33674-33677, 33681-33685, 33707-33720; September 33748-33750

1911

January 35958-35960, 35978-35980, 35986-35989

All were fitted with 12" (305 mm) piston valves. Firebox heating surface included 28 sq ft (2.6 sq m) of arch tubes. This number was not noted in the 1918 Union Pacific locomotive diagram book, but is deduced from its presence in the 1936 version. Although the latter entry describes a superheated upgrade, the lack of modification to the other parts of the locomotive suggest that the arch tubes were in the original configuration as well.

See Locobase 6609 for the superheated update.

Class P-1 to P-6 - superheated (Locobase 6609)

Data from 1936 Union Pacific locomotive diagram book supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange.

Superheating the UP's Harriman light Pacifics (see Locobase 4408) gave the usual fillip to performance. Unlike other conversions of this sort, however, the rearrangement of tubes and flues resulted in a net gain of evaporative heating surface.

Thirteen of the class had been retired by 1930 and of the earlier batches were kept in service as late as 1941. All but one of the 1911 series (2851-2859) remained in use after World War II. (2850 was retired in May 1940.)

Class P-10 (Locobase 6611)

Data from 1918 and 1936 Union Pacific locomotive diagram books supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. Works numbers were 1424-1448 in 1914.

As noted in Locobase 6610, these P-10s were identical to Brooks's P-8 and P-9 classes except for a slightly larger superheater.

In addition to the parent line's 20, Oregon Short Line took an additional 5 P-10s and numbered them 3129-3133.

Class P-11 - streamlined (Locobase 15904)

Data from Union Pacific locomotive diagram supplied by Chris Hohl in September 2014( and originally presented at []) in support of his contention that this locomotive deserved a separate entry. See also Utah Rails entry based on Gordon McCulloh's research originally published in an 12 December 2005 email and archived at [], last accessed 23 September 2014.

Locobase 6612 describes the original set of Baldwin-built Pacifics from which this streamliner was produced.

Wes Barris's steamlocomotive site ([], last accessed 27 February 2010) shows the results of streamlining the 2906 in 1937. He notes that it was one of two (the other being Mountain 7002) that were held in reserve to substitute for the diesels that usually pulled the Forty-Niner all-Pullman train between Chicago and San Francisco five times a month between 1938 and 1941. The 2906's run linked Omaha and Cheyenne.

Locobase has to say that the aesthetic result falls short of several other such makeovers. It had the "upside-down bathtub" look of some of the New York Central engines, but the casing was painted in a chocolate brown while the valences that hung down from the outside edge of the running board were Scarlet with thick Armour Yellow edging. Whiskers flowed from a central yellow raised nose stripe and chrome accents glitzed the exterior as did the red edging on the tires on all axles. The thick red band on the valence extended back along the tender.

On the other hand, the makeover included the provision of Timken roller bearings on all axles and rods, needle bearings in the valve gear, and lighter weight vanadium steel main and side rods. Weight on drivers came in almost 5 tons heavier than the original and total engine weight climbed to 308,700 lb (an increase of over 7 1/2 tons). McCulloh quoted William Kratville's 1960 account (in his Motive Power of the Union Pacific, p, 174) on the costs: "Streamlining of the 2906 cost $16,751 to install. Removal costs [in 1941]were $12,732 including many new parts and changing the position of the headlight. Roller-bearings cost $15,452."

Class P-11/P-13 (Locobase 6612)

Data from 1936 and 1946 Union Pacific locomotive diagram books supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. See also DeGolyer, Vol 69, pp. 130+.

The Oregon-Washington Railroad & Navigation Company bought two of this class (works numbers 51483, 51522 in March 1919, road numbers 3226-3227). Ten were supplied to the parent UP as 2900-2909 a year later (works numbers 53468 in July 1920; 53510, 53529-53530, 53577 in August; 53618-53619, 53712-53713, 53761 in September).

Last in a series of Pacific batches delivered to the UP, this Baldwin set had two more tubes than the others. Otherwise it was identical to the superheated P-9s and not derived from the USRA Pacific designs of that same year. Fifteen-inch (381 mm) piston valves fed the cylinders. Power reverse gear was Ragonnet Type B.

See Locobase 15904 for the streamlined 2906.

The 69"-drivered Oregon Short Line P-12s delivered in the same period to the same design are described in Locobase 11183.

Most of the UP 2900s from this batch were retired in late 1947. Both OWNRR engines lasted quite a bit longer and were retired in December 1954.

Class P-2 (Locobase 3315)

Data supplied by table from June 1906 American Engineer and Railroad Journal (AERJ). See also data from"Report of Committe on Power-Chicago, Rock Island & Pacific Railway-Descriptions of Standard Types of Locomotives," American Engineer and Railroad Journal, Volume 79 ( March 1905), pp. 84-86; and DeGolyer, Volume 28, pp. 20-21. See also H V Wille [assistant to the superintendent of the Baldwin Locomotive Works], "Balanced Compound Locomotives", Railroad Gazette, Volume XL [40], No. 24 (15 June 1906), pp. 644-647. Works numbers were 25687-25689, 25717 in May 1905.

Built to the Harriman P-77 22/28 143 classification, this class of high-drivered passenger Pacifics were balanced compounds when delivered. Like the earlier Vauclain compounds, the two cylinders on each side--1 HP, 1 LP was served by a 15" (381 mm) piston valve.

But, unlike the Vauclain compound, in which both the high and low-pressure cylinders shared a common crosshead whose main rod's big end drove on the outside of the driver. In these engines, each HP cylinder in a balanced compound drove a crank on the same axle as the LP cylinders. So four rods moved four crank points on the same axle in the same revolution.

In the four ORN engines, all four cylinders drove the second axle with the HP inside, LP outside. The inside cranks were built up in a two-web layout.

They were in fact something of an experiment, a deviation from the basic HCS simple-expansion Pacific design. In 1923, they were rebuilt as simple-expansion engines with 22 x 28 cylinders and given Walschaert gear. At that point they were rated at 29,920 lb tractive effort. By this time, the OR&N had been absorbed by the Union Pacific and the class (designated P-2) received numbers in the 3200 series.

The 197 of this class (Baldwin works # 25717 and UP 3203) has been preserved. See [] for details on the restoration to service.

Class P-3 - superheated (Locobase 8347)

Data from UP 11 - 1946 locomotive diagram book supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange.

Like the other Harriman Common Standard Pacifics, this OSL class gained heating surface when upgraded to a superheater. But this boiler retained more evaporative heating surface to begin with. Some were never converted and began retiring in 1933; others lasted through World War II and were retired by 1947.

Class P-7 (Locobase 11379)

Data from "Pacific Type Locomotive Arranged for Burning Lignite", American Engineer and Railroad Journal (October 1910), pp. 404-406. Baldwin's 1911 works numbers were 36416-36417. Alco's Brooks Works added 6 more in 1913; works numbers were 53349-53354.

AERJ reports that these two locomotives were completed as lignite-burners because of the success the OWR&N had enjoyed with the Mikados it had put in service the year before. See Locobase 1405 for a description of the lignite-burning grate.

Baldwin diverged from the standard Associated Lines (Harriman) Standard Pacific design in several other respects besides the much larger grate. The builder installed even larger piston valves, however, that measured 15" in diameter. Other changes included larger-diameter and longer firetubes.

This class was later converted to oil burning and superheated; see Locobase 11380.

Class P-7 - superheated (Locobase 11380)

Data from OWRR&NCo 2 - 1938 and UP 11 - 1946 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange.

Locobase 11379 describes the acquisition of the original lignite-burning engines in 1911 and the differences between this small class and most of the other UP locomotives of that period, which were built to the Harriman Common Standard. Baldwin added 3226-3227 (works numbers 51483, 51522 in March 1919).

When the OWR&N updated this class with a superheater, it converted them to oil burning as well. Three saw only a modest boiler pressure increase to 200 psi with the other 5 acquiring 220-psi boilers. The earliest 3 were later updated to that higher figure. The 1946 diagram credits the boilers with 2 fewer boiler tubes and no arch tubes in the firebox.

Class P-77 / P-1 (Locobase 7263)

Data from SPLA&SL Locomotive Diagram book (the Salt Lake Route) supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. See also DeGolyer, Volume 26, pp. 200+ and Volume 27, pp. 270+. Works numbers were 23562-23563, 23591, 23616, 23630, 23638 in January 1904; 24905-24906, 24919-24920, 24932-24934 in December; 24954-24955, 24959-24960, 24975-24977, 25002 in January 1905; 31594-31595 in August 1907; 31644-31645 in September

The first class of 4-6-2s for this Union Pacific component, these Harriman Common Pacifics were acquired well before the UP assumed full control of the LASL. The high drivers show the express-passenger service intent of these engines, while the relatively small firebox shows the transitional nature of the design.

400-412 were delivered as coal burners with tenders carrying 14 tons of coal. 413-420 were built as oil burners .

Note: Alco-Schenectady delivered four more locomotives to the Oregon-Washington Railroad & Navigation in 1904 (works numbers 30035-30038 in August 1904) as road numbers 190-193. Renumbered 3204-3207 in 1915.

The class was retired over many years, the first being withdrawn in 1926, the last not until 1954. Most were superheated later in their careers; see Locobase 6609.

Class P-8 (Locobase 7264)

Data from SPLA&SL Locomotive Diagram book (the Salt Lake Route) supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. (Thanks to Randal O'Toole for his 28 August 2022 email noting an incorrect citation for Partington's paper.)

These were considerably more powerful locomotives than the Harriman light Pacifics shown in Locobase 4408. For the SP, LA & SL (LASL), the original delivery of these engines was with a saturated-steam boiler as shown in the specs. Compared to other 4-6-2s delivered with "wet" cylinders, this was one of the biggest designs in sheer capacity (heating surface, grate area (e.g.)) and in adhesion weight.

3433 starred in the gripping Hazards of Helen episode "Escape on the Fast Freight" in 1915 starring Helen Holmes. Unlike the episodes featuring Santa Fe's 2-10-10-2 (Locobase 418) and the SPLA&SL's 3201 (Locobase 7262), this installment betrays Hollywood's usual preference for art over accuracy. It shows two different locomotives heading up the same passenger train, the second scene giving us 3433 gliding to a stop in the station. See Locobase 418 for more details on these cliffhangers.

Locobase has determined that this is one of the locomotives to which the Estimating Engineer for Alco compared his company's #50000 in James Partington, "Avoidable Waste in Locomotive Operation as Affected by Design", No. 1816, December 1921 in Transactions of the American Society of Mechanical Engineers, Volume 43 (New York: The Society, 1922), 987-1011. He chose not to identify any of these rivals, but the UP books show that this class matches up with Partington's mystery locomotive.

Not too long afterward, the class was superheated. See the Union Pacific P-8 entry at Locobase 3303.

Class P-8/P-9-s (Locobase 3303)

Data from 1918 and 1936 Union Pacific locomotive diagram books supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. (Thanks to Randal O'Toole for his 28 August 2022 email noting an incorrect citation for Partington's paper.)

Locobase has determined that this is one of the locomotives to which The Estimating Engineer for Alco, compared his company's #50000 in James Partington, "Avoidable Waste in Locomotive Operation as Affected by Design", No. 1816, December 1921 in Transactions of the American Society of Mechanical Engineers, Volume 43 (New York: The Society, 1922), 987-1011. He chose not to identify any of these rivals, but the UP books show that this class matches up with Partington's mystery locomotive.

These were considerably more powerful locomotives than the Harriman light Pacifics shown in Locobase 4408 and they were superheated from the beginning. In addition to the UP numbers shown in the specs, additional locomotives of this class went to subsidiaries as follows:

Oregon Short Line 1912 10 Alco-Schen 3114-3123 P-8

OSL 1913 5 Alco-Brooks 3124-3128 P-9

Los Angeles & Salt Lake

1912 6 Alco-Schen 3176-3181 P-8; See Locobase 7264 for the original, saturated-steam version.

OWR&N 1913 8 Alco-Brooks 3218-3219 P-7, 3220-3225 P-9.

Lima's batch, which had somewhat more superheat, is shown in Locobase 6611. The P-8s & P-9s were later modified to the P-10's superheater standard.

Class P12 (Locobase 11183)

Data from 1946 Union Pacific locomotive diagram books supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. See also DeGolyer, Vol 56, pp. 187+. Works numbers were 51197-51198, 51277, 51346, 51445 in February 1919.

Locobase 6612 describes the last in a series of Pacific batches delivered to the UP in 1919-1920. Like those, this OSL set was identical to the superheated P-9s and not derived from the USRA Pacific designs of that same year. Unlike the P-11 and P-13s, however, this batch had 69" drivers and trailed an oil-fuel tender.

Tube and flue thicknesses were expressed in decimal gauge. Firebox heating surface included 28 sq ft (2.6 sq m) of arch tubes. Relatively large cylinders took their steam through 15" (381 mm) piston valves.

Like the other engines, this class remained in service until the end of steam on the UP. 3134 retired in September 1954, 3135-3136 and 3138 went in January 1955, and 3137 completed the retreat in March 1955.