At the same time the Northern Pacific was designing Pacifics and Mikados for the standard day-to-day freight and passenger work, it was also designing Mallet compounds for the extremely steep (2.2 percent) grades of the railroads as well as for other heavy freight work. The first successful Mallet compound was constructed in 1906 by the Baldwin Locomotive works for the Great Northern Railway Company. It was originally designed to pull heavy freight trains over the 2.2 percent grades of the Cascade Mountains. (176- Charles Wood, Lines West Seattle [WA] Superior Publishing Company, 1967 p. 43) Soon after the new 2-6-6-2s were delivered to the Great Northern, the Northern Pacific borrowed one of the locomotives and under the direction of Mr. W.L. Kinsell, the Mechanical Engineer, tested the locomotive between Livingston, Montana, and Bozeman Pass, a distance of 12.5 miles with a grade of 1.9 percent. As a result of these tests, the Northern Pacific placed an order with the Baldwin Locomotive Works for 16 duplicates of the Great Northern design. (177-Baldwin Locomotive Works, Mallet Articulated Compound Locomotive, Philadelphia [PA] BLW 1908 p. 30) The only difference between the two locomotives was in the design of the cab and the type of tender used (178-Wood, Main Street of the Northwest Seattle [WA] Superior Publishing Company 1968 p. 85) They were delivered in August of 1907 and were put to work as helpers on freight trains up the steepest grades of the Northern Pacific. They were rated at 850 tons on a 2.2 percent grade compared to 600 tons for a W class 2-8-2 and 500 tons for a Y-5 Consolidation. (179-BLW Mallet Articulated Compound Locomotive [no page cited])
The 2-6-6-2 (Class Z) machines were compact with the firebox located over the last two driving wheels on the second set of drivers. The trailing truck was rigid and did not swivel. Although the 30 foot driving wheel base allowed the locomotive to wiggle around virtually any curve on the railroad, the shallow firebox restricted the locomotive to short periods of full capacity work while the small driving wheels slowed it to speeds of less than 15 miles an hour. Despite the confidence of one Baldwin official to increase the speed of the Class Z machines to 20 or 25 miles an hour, the results on the roadbed discouraged such speeds. (180-Letter from M. Birney [Traveling Engineer for Baldwin] to Samuel Vauclain [President of the Baldwin Locomotive Works] November 3, 1907. Carbon in Northern Pacific Files, ME File 4972, Box 157, Como Shops) Compared to some of the later 2-8-2 type locomotives, the Class Z Mallets were not large. The low pressure cylinders were 33 by 32 inches and the high pressure [cylinders] were 21 1/2 by 32 inches; steam pressure in the boiler was 200 pounds per square inch. The firebox was square on tops instead of round. The square type of firebox was known as the Belpaire firebox and was only used on the Class Z Mallets. The entire locomotive rode on relatively small 55 inch driving wheels and weighted 355,000 pounds in working order. The tractive effort of 62,8000 pounds, while greatest on the road at that time, was even less than the W-3 class Mikados built six years later. (181-Locomotive Specification Board p. 262, lists the tractive effort at 62,800, while the Locomotive Data Book, p. 80. lists it at 67,500. According to my own calculation the 62,800 is the correct figure.) [Frey, Robert L. Technological History of Northern Pacific Steam Locomotives Ann Arbor: [MI] University Microfilms 1966 pp. 270-72]
The Northern Pacific has the distinction of employing a larger number of the Mikado-type locomotives than any other road in the country. The first order of this type consisted of 25 locomotives of which six were tandem compound built by the American Locomotive Company in 1904. These were almost the pioneers of the type in this country, so far as modern heavy power is concerned, and are simple engines having 24 inch by 30 inch cylinders, 63 inch driving wheels, 200 pounds of steam pressure and have a total weight on drivers of 195,000 pounds. The tractive effort is 46,630 pounds. At that time these locomotives were the heaviest on that road an among the heaviest [p. 1] in the country. Since 1904 various improved designs have been developed from the original engines until at the present the Northern Pacific has in operation 470 locomotives of the 2-8-2 type built by the American Locomotive Company.
The latest addition to this equipment is 50 locomotives having 28 inch by 30 inch cylinders, 63 inch driving wheels, 180 pounds steam pressure and a tractive effort of 57,400 pounds. The total weight on drivers is 240,500 pounds. While the first engines did not have combustion chambers, an order which followed shortly after was so provided, the design being prepared by David Van Alstyne, then Superintendent of Motive Power. The various orders which have followed have in each case had a combustion chamber and the later engines also have superheaters.
As part of the latest order, the American Locomotive Company has also delivered ten Mallet locomotives of the 2-8-8-2 type, which are a development of the previous design of articulated locomotive that has been very successfully used in helper service on this road.
That the new locomotives are proving to be all that could be expected is evident from the following description they are doing on various divisions.
They have been put into service between Mandan, N.D., and Paradise, Mont., including the Yellowstone, Montana, and Rocky Mountain Divisions. The Yellowstone Division, Mandan, N.D., to Billings, Mont., is 441 miles long and has a maximum grade of one per cent, against both east and westbound traffic. The new Mikado locomotives (Class W-3) are hauling 1,800 tons over this district at an average speed of from eight to ten miles an hour.
On the Montana Division, Billings, Mont., to Helena, Mont., a distance of 239 miles, there is a ruling grade westbound from Livingston to Muir, twelve miles long, of 1.8 per cent, and eastbound from Bozeman to Muir, thirteen miles long, of 1.9 per cent; all grades compensated. West of Bozeman the maximum grade is 0.8 per cent, against eastbound traffic. In this territory the Mikados are hauling 1,800 tons with a class Z-1 Mallet helper between Bozeman and Muir. The Class Z-1 Mallet is a 2-6-6-2 type, having cylinders 20 inches by 31 inches by 30 inches, saturated steam, 210 pounds pressure, weight on drivers of 262,350 pounds and a tractive effort of 58,100 pounds.
Pervious to receiving the new Mikados, trains of 1,400 tons were hauled over this territory by a Class W (2-8-2 type) locomotive using the same helper. The Class W has cylinders 24 inches by 30 inches, saturated steam at 200 pounds pressure, weight on drivers of 203,000 pounds, and a tractive effort of 46,600 pounds.
The Rocky Mountain Division, from Helena, Mont., to Paradise, Mont., is 219 miles long. From Helena to Blossburg there is a maximum grade against eastbound traffic, 17 miles long, of 2.2 per cent. The balance of the division has a grade against eastbound traffic from Missoula to Garrison, 68 miles of 1.4 per cent; all grades are compensated. One Class W-3 locomotive hauls 2,600 tons from Missoula to Garrison at an average speed of 16 miles an hour. The Class W hauls 2,200 tons at an averages speed of 12 miles an hour. Between Garrison and Blossburg one Class Z-1 helper is used. On this division the new Mikados are making 41,600 ton mile hours as against 26,400 for the Class W Mikados, an increase of 57.6 per cent.
Between Helena and Blossburg a Class W-3 locomotive with a Class Z-3 helper is hauling 1,750 tons with no increase in coal over that formerly used by a Class W and a Class Z-1 handling 1,350 tons. This is an increase of 29.6 per cent in train load, with no increase in coal consumption.
The new Class Z-3 Mallets are used on the Rocky Mountain and Seattle Divisions, four coal burners on the Rocky Mountain Division and six oil burners on the Seattle Division. The grades and trains on the Rocky Mountain Division are described above, these locomotives being used as helpers between Helena and Blossburg.
The Seattle Division, from Ellensburg, Wash., to Auburn, Wash., is 105 miles long, crossing the Cascade Mountains through Stampede Tunnel west of Ellensburg at an elevation of 2,837 feet above sea level. These locomotives are handling 2,200 tons from Auburn to Ellensburg at a speed of from eight to 14 miles per hour, on a total oil consumption of 2,645 gallons. From Auburn to Lester, a distance of 43 miles, the average grade is one per cent. From Lester to Easton, a distance of 24 miles, there is a ruling grade of 2.2 per cent for ten miles. The Class Z Mallet helper above mentioned is used from Lester to Martin. Westbound, the Z-3 locomotive handles a time freight of 1,900 tons from Ellensburg to Auburn on 1,726 gallons of oil, having a Class Z (2-6-6-2) Mallet helper on the 2.2 per cent grade.
[p.2] The design of the new 2-8-2 type locomotives combines a superheater, firebrick arch, smoke consumer tubes in the sides of the firebox and a 36 inch combustion chamber. Included in the design are the builders' latest design of valve stem guide, piston rod extension guide, outside steam pipes, power reverse gear, and outside bearing trailing truck.
Both the oil burning and coal burning Mallets have superheaters and power reverse gears; the four coal burning engines are equipped with an arch. Heavy Power for the Northern Pacific Railway Age Gazette August 29, 1913, pp. 337-8]
Author: John A. Phillips, III. Title: From Z to Z-3.