Union Pacific class MK-1 explained

Union Pacific class MK-1
Powertype:steam
Fueltype:lignite
Fuelcap:10 tons
Watercap:9,000 US gallons
Tendertype:Vanderbilt tender in later batches
Builddate:1910-1911
Totalproduction:86
Whytetype:2-8-2
Cylindercount:2
Cylindersize:23¾" × 30"
Valvegear:Walschaerts
Leadingdiameter:30½"
Driverdiameter:57"
Trailingdiameter:36"
Drivers:16 ft
Engine Total:34 ft 8 in
Wheelbasewithtender:64 ft 7 in
Boilerpressure:180 psi
Firearea:70 sq ft
Fireboxarea:267 sq ft
Tubearea:5,292 sq ft
Totalsurface:5,559 sq ft
Smalltubediameter:495× 2"
Lengthinside:20 ft 6 in
Tractiveeffort:45,300 lbf
Locoweight:263,100 lb
Leadingbogie/Pony:24,100 lb
Weightondrivers:204,450 lb
Trail Bogie/Pony:34,550 lb
Operatorclass:UP: MK-1
Fleetnumbers:1900-1929, 2000-2014, 2100-2140[1]
Preservedunits:No. 2005
Disposition:One preserved, remainder scrapped

The Union Pacific class MK-1 was a class of 2-8-2 'Mikado' type steam locomotives that were built by the Baldwin Locomotive Works originally for the Oregon Railroad and Navigation Company (OR&N), Oregon Short Line Railroad (OSL) and Union Pacific Railroad (UP) in 1910 and 1911.

History

In 1910, the Oregon-Washington Railroad and Navigation Company (OWR&N) purchased a 2-8-2 'Mikado' locomotive from the Baldwin Locomotive Works and had this single locomotive numbered 440, this locomotive would be renumbered as 500 in 1911, and renumbered to 2100 in 1915.

In 1911, the OWR&N would order another 40 of these locomotives from Baldwin where they were originally numbered as 501–540, but renumbered as 2101–2140. The Oregon Short Line Railroad (OSL) would order 15 locomotives from Baldwin and numbered them as 1100–1114, but renumbering them to 2000–2014 in 1915. The Union Pacific Railroad (UP) would order 30 locomotives from Baldwin where they numbered them as 500–529, renumbering them to 1900–1929 in 1915

OSL No. 2000 was sold to the Spokane International Railroad (SI) in 1947.

Design

The locomotives were designed from the outset to burn low-quality lignite coal as a fuel. In general they followed typical practice of the day for Baldwin designs and locomotives for Harriman's Associated Lines, but with some changes to the boiler and firebox. The boiler was cylindrical and the firebox was stayed with 400 radial rod stays, rather than girder crown stays. Given the poor quality of the fuel, a larger boiler was needed than usual for the power of the locomotive. The heating surface of 5,559 sq ft considerably exceeded that of the nearest comparable design, with 4,466. The grate bars were arranged as large cast grate sections spanning half the width of the firebox and arranged for rocking to clear ash. Airflow was provided by an unusually great number of narrow slots, to suit lignite.[2] The brick arch was deeper than usual, again to suit lignite, and was supported by four arch tubes. The boiler, as built, was unsuperheated and had 495× 2" tubes.

At the time this was the largest Mikado built, although not quite the most powerful or with the most weight on its drivers.

Superheating

In 1912, the boiler was rebuilt to provide superheating. Half of the tubes were removed in favour of 36 larger flues containing superheater elements. Total heating area was reduced to 5,118 sq ft, although still large in its class.

Oil firing

Some were later converted to oil firing.

Preservation

Only one member of the class is in preservation, No. 2005, which is on static display at Ross Park based in Pocatello, Idaho.

Fleet numbers

Union Pacific

Road numberBuilt dateSerial numberFirst run dateRetirement dateDisposal dateNotes
19001911----Scrapped
19011911----Scrapped
19021911----Scrapped
19031911----Scrapped
19041911----Scrapped
19051911----Scrapped
19061911----Scrapped
19071911----Scrapped
19081911----Scrapped
19091911----Scrapped
19101911----Scrapped
19111911----Scrapped
19121911----Scrapped
19131911----Scrapped
19141911----Scrapped
19151911----Scrapped
19161911----Scrapped
19171911----Scrapped
19181911----Scrapped
19191911----Scrapped
19201911----Scrapped
19211911----Scrapped
19221911----Scrapped
19231911----Scrapped
19241911----Scrapped
19251911----Scrapped
19261911----Scrapped
19271911----Scrapped
19281911----Scrapped
19291911----Scrapped
2000April 1911----Sold to the Spokane International Railroad in 1947. Scrapped
20011911----Scrapped
20021911----Scrapped
20031911---1952Scrapped
20041911----Scrapped
2005April 191136367-1958-On static display at the Ross Park in Pocatello, Idaho.
20061911----Scrapped
20071911----Scrapped
20081911----Scrapped
20091911----Scrapped
20101911----Scrapped
20111911----Scrapped
20121911----Scrapped
20131911----Scrapped
20141911----Scrapped
21001910---1955Scrapped
21011911----Scrapped
21021911----Scrapped
21031911---1951Scrapped
21041911----Scrapped
21051911----Scrapped
21061911----Scrapped
21071911----Scrapped
21081911----Scrapped
21091911----Scrapped
21101911----Scrapped
21111911----Scrapped
21121911----Scrapped
21131911----Scrapped
21141911----Scrapped
21151911----Scrapped
21161911----Scrapped
21171911----Scrapped
21181911----Scrapped
21191911----Scrapped
21201911----Scrapped
21211911----Scrapped
21221911----Scrapped
21231911----Scrapped
21241911----Scrapped
21251911----Scrapped
21261911----Scrapped
21271911----Scrapped
21281911----Scrapped
21291911----Scrapped
21301911----Scrapped
21311911----Scrapped
21321911----Scrapped
21331911----Scrapped
21341911----Scrapped
21351911----Scrapped
21361911----Scrapped
21371911----Scrapped
21381911----Scrapped
21391911----Scrapped
21401911----Scrapped

Notes and References

  1. Web site: McCullough . Gordon . UPRR Steam Locomotive Roster by Class and Number . Union Pacific Historical Society . 2024-09-22.
  2. May 1908 . Burning Lignite Coal In Locomotives . . 161–163 .

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