2-8-8-4 Yellowstone Type Locomotives

DM&IR Yellowstone

Only 72 Yellowstones were built (in five different classes). Each class of Yellowstone was a different design (except for the two classes owned by the DM&IR). The design was usually dictated by the specific needs of the railroad that received them.

Northern Pacific class Z-5

The first Yellowstone was built in 1928 by ALCO for the Northern Pacific for running throughout the high speed plains of North Dakota. It would turn out to be the one and only Yellowstone that ALCO would build.

NP wanted to burn low-grade Rosebud coal (obtained from mines along the line) in their locomotives. This required the Yellowstone to be designed with a huge (the largest ever used on a steam locomotive) firebox (182 sq. ft.). The front half of the firebox was over the two rear pairs of drivers and the trailing truck (which was equipped with a booster).

It was the largest steam locomotive in the world (at that time) and ALCO celebrated by serving dinner to 12 people seated in the firebox! NP asked for bids for 11 more like it and in 1930 Baldwin got the job. The NP Yellowstones steamed poorly and produced less that 5,000 HP. NP found that the grates were simply too large to maintain a high temperature and complete combustion. The combustion problem was solved by blocking off The front two feet of the firebox on each locomotive. At some point the Z-5s were upgraded with roller bearings.

Southern Pacific class AC-9

Most of Southern Pacifics "big steam" were of the Cab Forward design (a backwards Yellowstone). However, not all of the SP "big steam" was required to run through the snow sheds of the Sierras. In 1939 the SP received 12 Yellowstones from Lima for use throughout the southern part of the SP system. Unlike the Cab Forwards, the class AC-9 locomotives were built as coal burners. They were later converted to burn oil. Also, the AC-9 class had a grate area of 146 sq. ft. rather than the 139 sq. ft. of their cab forward siblings. With their skyline casings and striped cowcatcher-pilots, they could almost be considered streamlined. They were retired between 1953 and 1956.

Duluth, Missabe & Iron Range classes M-3 and M-4

In the late 1930s the DM&IR was in need of new locomotives that would be able to handle 115-car, 8750-ton trains over .62% grades without stalling. The Western Pacific 2-8-8-2 was used as a basis for its design. The larger cab required a longer and heavier frame, therefore a 4-wheel trailing truck was used. Roller bearings were used on all locomotive and tender axles. The DM&IR was the only road who chose to use "pedestal" or "centipede" tenders with their Yellowstones. THE DM&IR Yellowstones also had gray boiler jacketing.

DM&IR was pleased with the first batch (class M-3) of 8 received from Baldwin in 1941 so they ordered 10 duplicates (class M-4). They were completed late in 1943 after much of DM&IR's traffic had subsided, so some of the M-4s were leased by and delivered directly to the Denver & Rio Grande Western. The following winter the D&RGW again borrowed the 2-8-8-4s for use as helpers over the 10,239-foot Tennessee Pass crossing of the continental Divide. The D&RGW sent a telegram to the DM&IR stating that the Yellowstones were the finest steam locomotives to ever operate on its road.

On the DM&IR they were used as the main road power to pull ore trains throughout the Duluth area. For the most part, ore trains had to be pulled downhill to the ore docks on Lake Superior in Duluth and Two Harbors. These trips did not require the enormous pulling force of the Yellowstones. Surprisingly, the limiting factor (as far as what the iron range locomotives could pull) was the 2.2 percent grade from Duluth up to the yards in Proctor. The ore cars had to be returned empty to these yards for sorting.

The Yellowstones were sometimes used to pull empties up this hill from Duluth to Proctor. However, the classic 'hill' power was the older modified 2-8-8-2 'Hill' engines with their extra air tanks on top of the boiler. Newer 2-10-4s and 0-10-2s were also used on the 'Hill' at least in the mid-late 50's when steam was still on the line. Someone once told me that he spoke to a couple people (including the diesel shop foreman who used to fire the Yellowstones and a former engineer on the Yellowstones) at the Proctor roundhouse while 227 was being restored in preparation for its display in the museum in Duluth. They said that it was possible to empty the tender of almost all coal and water of a Yellowstone while pulling a load of empty ore cars up the hill from Duluth to Proctor. This is to say: 25,000 gallons water and 25-26 tons of coal! This is hard to believe and perhaps it is a bit of an exaggeration, but it does show that this was one of the more difficult tasks for the Yellowstones.

All of the DM&IR Yellowstones were all retired between 1958 and 1963.

Baltimore & Ohio class EM-1

The EM-1s were the last articulated steam locomotives built for the B&O. Actually, the B&O did not want the EM-1s. Instead they wanted diesels. However, because of restrictions imposed by the War Production Board, the EM-1s were delivered from Baldwin in 1944 (7620 - 7619) and 1945 (7620 - 7629). For this wheel arrangement, they were relatively modest in size, but very successful. Originally, they worked on the Cumberland Division, a very physically difficult stretch of the B&O, with numerous heavy coal trains, as well as fast freights. The main district served by the EM-1 was the line from Cumberland towards Grafton, WV. Later, as diesels took over this assignment, the class was shifted to the Pittsburgh Division, where they primarily handled Lake Mineral traffic, plus trains between Wheeling and Pittsburgh. The class was renumbered 650-679. They started to be scrapped in 1957, and all were off the roster by 1960.

A Comparison of Yellowstone Designs

This table compares the various Yellowstone designs along with that of the UP Big Boy and Western Pacific 2-8-8-2. All Yellowstone classes employed simple steam expansion and thus none can be called "mallets".

TypeNP
Z-5
SP
AC-9
DM&IR
M-3
DM&IR
M-4
B&O
EM-1
UP
4884-1
WP
M-137/151
Series50003800-3811220-237228-2377600-76194000-4019251-260
Cyl:dia x stroke26x3224x3226x3226x3224x3223.75x3226x32
Driver diameter6363.56363646863
Boiler pressure250250240240235300250
Grate area182139.3125125117.5150145
Evaporative heating surface7673691867806758/678052985889
Superheater heating surface321928312770277021182466
Weight on drivers554,000531,200560,257564,974485,000540,000552,700
Total engine weight715,000689,900695,040699,700628,700762,000665,100
Tender weight401,000400,700436,635438,335382,000427,500408,250
Tractive force engine145,930124,300140,000140,000115,000135,375137,000
Tractive force booster13,400NoneNoneNoneNoneNone13,900

USA and Canadian Railroads that used 2-8-8-4 Yellowstone Type Locomotives

Surviving Examples of 2-8-8-4 Yellowstone Type Locomotives

No.ClassF.M. WhyteGaugeRailroad LineLocationStatusBuilder InformationNotes
227M-32-8-8-44'-8½"DM&IR Lake Superior Railroad Museum, Duluth, MNdisplayBaldwin #62533, 1941
225M-32-8-8-44'-8½"DM&IR US 2, Proctor, MNdisplayBaldwin #62531, 1941
229M-42-8-8-44'-8½"DM&IR D&IR Depot, Two Harbors, MNdisplayBaldwin #64708, 1943

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