Class H-1 (Locobase 8822)

Data from GN 1-1929 locomotive diagram book supplied in May 2005 by Allen Stanley from his extensive collection.

Among the first Pacifics to go into service in North America, these passenger engines had slide valves and saturated boilers in front of their Belpaire fireboxes. They had a relatively long stroke, but otherwise sat in the middle of 4-6-2s delivered with saturated boilers.

As far as Locobase can tell, these were never superheated.

Class H-2 (Locobase 8819)

Data from GN 1-1929 locomotive diagram book supplied in May 2005 by Allen Stanley from his extensive collection. Roster information from http://www.greatnorthernempire.net/index2.htm?GNEGNPrototypeDrawingsSteam.htm, a website authored by Ben Ringnalda.

Baldwin builders' numbers comprised:

28136, 28146, 28157-28159, 28188-89, 28203, 28207, 28229, 28239-40, 28309, 28316-28318, 28377-78, 28230, 28523 in 1906 and 31211-31214, 31276-77, 31301-31303, 31332-33, 31350-51, 31415, 31448 in 1907.

The largest class of Pacifics to go into service on the GN, these had saturated boilers, slide valves, and Belpaire fireboxes. For some reason, although most were converted to H-3 or superheated in the early teens, 10 operated into the 1930s in their original configuration.

Locobases 8820-8821 show the two main variants of superheated upgrades.

Class H-2-S/H-3-S - 2 "" tubes (Locobase 8821)

Data from GN 1-1929 locomotive diagram book supplied in May 2005 by Allen Stanley from his extensive collection.

Locobase 8819 shows the original H-2 Pacifics. In the early teens, most were superheated and supplied with 12" piston valves. Locobase 8820 describes the engines that had the less-drastic modification. The larger number received a new boiler to go with its Belpaire firebox, one in which the 2 1/4" tubes of the original were replaced by a larger number of 2" tubes.

In the 1920s, some were upgraded to H-3-S with a new boiler of similar dimensions in which the working pressure was raised to 210 psi. This resulted in a tractive effort of 42,900 lb.

Class H-2-S/H-3-S - 2 1/4"" tubes (Locobase 8820)

Data from GN 1-1929 locomotive diagram book supplied in May 2005 by Allen Stanley from his extensive collection.

Locobase 8819 shows the original configuration of the GN's H-2 Pacifics. For most of them, it was a layout with a short life. In the early teens, most were superheated and Heron 8 1/2" piston valves installed in a universal steam chest. Later, almost all of the engines later received 12" piston valves.

This variant retained the 2 1/4" tubes ahead of their Belpaire fireboxes, but reduced the number by 122 when the shops added 30 flues. In the 1920s, some were upgraded to H-3-S with a new boiler of similar dimensions in which the working pressure was raised to 210 psi. This resulted in a tractive effort of 42,900 lb.

Class H-4 - Lima (Locobase 3173)

Data from GN 1-1929 locomotive diagram book supplied in May 2005 by Allen Stanley from his extensive collection.

These follow-on locomotives from Lima had slightly less evaporative heating surface, slightly more superheater than the Baldwins of 1909.

Class H-4 -- Baldwin (Locobase 146)

Data from GN 1-1929 locomotive diagram book supplied in May 2005 by Allen Stanley from his extensive collection.

20 built by Baldwin in 1909, 25 more from Lima in 1913. Efficient engines that ran for more than 40 years. A 14 December 1914 Railway Age article describes the road over which these engines ran, noting that one 129-mile section had a maximum grade of 1% and that the Pacifics averaged 30 mph with 11-12 cars over that section.

Class H-5 (Locobase 8852)

Data from GN 1916 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive collection.

This is a mystery engine, possibly a one-only conversion of an H-2. (Other H-5s were later conversions of E-14 Ten-wheelers.) The square cylinder dimensions enclosed a large volume, a spacious Belpaire firebox hosted a broad grate, and both tube sizes were substantial as well.

Class H-5 / H-7 (Locobase 6450)

Data from GN locomotive diagram found on Ben Ringnalda's http://www.greatnorthernempire.net/images/GNP_2523Diagram.jpg (viewed 8 Jan 2005). A long article -- http://www.gn1355.org/mechanical_attributes_of_the_h5.htm (viewed 11 July 2005) -- describes both the E-14 and the H-5 Pacific that resulted from a substantial rebuild. It is based on a reference sheet originally drafted by Doug Bemrich for the GNR Historical Society and based on research by Bemrich and Larry Obermeyer, Jr. See Locobase 8815 for a similar rebuild of J-1 & J-2 Prairies to the H-6 Pacific class.

Belpaire firebox heating surface included 31 sq ft of arch tubes. The combustion chamber's area was included in the overall figure for firebox heating surface.

This class was rebuilt from E-14 Ten-wheelers to match approximately the capacity of the H-4 Pacifics (See Locobase 146 & 3173) that the Great Northern had bought before World War I. Compared to those off-the-shelf designs, the H-5 rebuilds had a longer wheelbase and noticeably higher axle loading. (The latter improved the factor of adhesion.)

The last 10 -- modfied in 1926-1927 and designated H-7 -- sported a trailing-truck booster that contributed 11,700 lb to starting tractive effort.

The article mentioned above thoroughly describes all of the modifications and is strongly recommended. Suffice it here to say that every significant steam-producing dimension, area, or volume was enhanced beyond not only the E-14, but also the H-4 Pacific. Direct heating surface percentage of total EHS, superheater percentage of total heating surface, ratio of heating surface to cylinder volume, efficiency and maintainability of the superheater. In sum, the effort proved well worth the cost.

The rebuilding program lasted most of the 1920s. New numbers were consecutive, but did not line up with the E-14s that preceded them. After the first 10 had been rebuilt in 1921-1925, the GN renumbered the class to make room for all 25. Six followed in 1926 and 9 completed the program in 1927.

The reconstruction proved of enduring value and very few significant changes were made to the class over the next 30 or so years of service. 1351 wrecked on 24 July 1941, the others were sold for scrap beginning in 1950 (1), 1951 (2), 1952 (8), 1953 (7), 1954 (2), and 1955 (3). One of the class -- 1355 - was preserved as an outdoor exhibit until its restoration began at the turn of the 21st Century.

Class H-6 (Locobase 8815)

Data from GN 4 - 1946 Loco Diagrams supplied in May 2005 by Allen Stanley from his extensive collection.

Turned out the Great Northern wasn't finished with some of the class of J-2 Prairies. Beginning in 1923, 15 were converted to Pacifics along the same lines as the H-5 conversions from E-14 Ten-wheelers (see Locobase 6450). The grate area in the Belpaire firebox stayed the same, although total direct heating surface increased, and the cylinders retained their long stroke.

The boilers grew through a further reduction in tube count in favor of two more flues and in the lengthening of all tubes and flues by 2 1/2 feet. Working pressure rose to 200 psi and the axle loading climbed to over 28 tons.