Northern Pacific Railroad Giant Freight Locomotive

A giant American locomotive that handles 4,000 tons trains on the Northern Pacific Railroad

THE NEW 2-8-8-4 ARTICULATED LOCOMOTIVE in service on the Northern Pacific Railway

THE NEW 2-8-8-4 ARTICULATED LOCOMOTIVE in service on the Northern Pacific Railway. It is claimed to be the largest and heaviest locomotive in the world.

THE American Locomotive Company recently completed at their works at Schenectady, N.Y., for service on the Northern Pacific Railway, a locomotive that is claimed to be the largest and heaviest yet built. This monster is of the single expansion “Mallett” articulated type, with a 2-8-8-4 wheel arrangement. It is known on the Northern Pacific Railway as the “Yellowstone” type.

This locomotive rides the rails on 34 wheels, including 12 on the tender. The total weight of engine and tender is 1,118,000 lbs., of which 717,000 lb. is the weight of the engine and 401,000 lb. that of the tender. Of the engine weight, 553,000 lb. is on the drivers; 48,500 lb. on the front truck, and 115,500 lb. on the trailing truck.

All four cylinders have the same diameter and stroke, 26 in. by 32 in. and the boiler — claimed to be the largest locomotive steam boiler ever built — operates at a pressure of 250 lb. The driving wheels have a diameter of 63 in. The engine develops a tractive power at 75 per cent, cut-off of 140,000 lb., and with the addition of the power of the trailer type booster with which it is equipped, 13,400 lb., has a total tractive power of 153,400 lb. Altogether this giant locomotive is capable of developing considerably over 6,000 h.p.

The overall length, between couplers, of the engine and tender is 125 ft., or three times the length of a standard American freight car. The height from the top of the rail is 16 ft. 4 in.

As it was desired to use semi-bituminous coal, obtained from an open pit owned by the company in southeastern Montana, special boiler requirements were necessary. This particular coal, while of comparatively low heating value, burns fiercely; and in order to obtain the required boiler horse power from the heat developed it was necessary to design the largest firebox and boiler ever applied to a steam locomotive. This boiler is conical in shape and is built for a working pressure of 250 lb. per sq. in. The grate area is 182 sq. ft.; the total evaporative heating surface 7,673 sq. ft., and the total superheating surface 3,219 sq. ft. The weight of the boiler alone is 165,000 lb., and more than 20,000 holes were drilled in it during construction. The firebox, including the combustion chamber, is 28 ft. 6 in. in length by 9 ft. 6 in. in width, making a total of 182 sq. ft. of grate area. The mechanical stoker is of special design and is capable of crushing, delivering and distributing to the firebox hourly a maximum of 22½ tons of coal.

The unusual length of the grates, 22 ft. 3 in., made it necessary to provide some additional means of manipulating a rake in the firebox, otherwise than through the fire-door. Two openings, 9 in. by 14 in., arranged on opposite sides of the firebox, were accordingly provided, They are situated about 16 ft. from the rear of the firebox, so that it is possible, with the ordinary style of firehook, to rake any part of the grate area iron the fire-door or either of the two side openings.

The tender has a capacity of 22,000 gallons of water and 27 tons of coal. The Coffin feedwater heater installed consists of two heaters welded together, so as to provide the same uniformity of steam passage as the single unit but with double its heat transfer capacity. Steam is admitted to the four cylinders by means of an American multiple throttle, which is power operated; and this is claimed to be the first installation of a power throttle device on a steam locomotive.

This new locomotive is in regular freight service over the 216 miles of Northern Pacific line from Mandan, North Dakota, to Glendive, Montana. This district has maximum grades of 1.1 per cent., the position and extent of the grades being such that double-heading is not practicable. Before this new engine was placed in service it was necessary for freight trains arriving at Glendive from the west with 4,000 tons to be split into practically two trains for movement from Glendive to Mandan. Precisely similar conditions prevailed at Mandan, and surveys have shown that to remodel the line so as to provide grades of four or five-tenths per cent, ruling grade would be a very costly undertaking.

The locomotive described here was designed to draw a 4,000-ton train in both directions over this district, and it has proved successful in reducing by at least 50 per cent, the train miles necessary to move freight traffic.

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