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.
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.
|Cyl:dia x stroke||26x32||24x32||26x32||26x32||24x32||23.75x32||26x32|
|Evaporative heating surface||7673||6918||6780||6758/6780||5298||5889|
|Superheater heating surface||3219||2831||2770||2770||2118||2466|
|Weight on drivers||554,000||531,200||560,257||564,974||485,000||540,000||552,700|
|Total engine weight||715,000||689,900||695,040||699,700||628,700||762,000||665,100|
|Tractive force engine||145,930||124,300||140,000||140,000||115,000||135,375||137,000|
|Tractive force booster||13,400||None||None||None||None||None||13,900|
|No.||Class||F.M. Whyte||Gauge||Railroad Line||Location||Status||Builder Information||Notes|
|227||M-3||2-8-8-4||4'-8½"||DM&IR||Lake Superior Railroad Museum, Duluth, MN||display||Baldwin #62533, 1941|
|225||M-3||2-8-8-4||4'-8½"||DM&IR||US 2, Proctor, MN||display||Baldwin #62531, 1941|
|229||M-4||2-8-8-4||4'-8½"||DM&IR||D&IR Depot, Two Harbors, MN||display||Baldwin #64708, 1943|