K-4 Steam Locomotive Model, PRR 1737

K-4 Steam Locomotive Model, PRR 1737

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This model shows a Pacific type passenger locomotive designed by the Pennsylvania Railroad. It was very successful with over 400 built by the Pennsylvania Railroad. It had a Walschaert valve gear, Belpair boiler, piston valves, and superheater.
Ever increasing train weights and schedules called for heavier power. The Atlantic had no sooner replaced the 4-4-0 than it was found wanting in power for certain assignments and the higher capacity 4-6-2 was introduced. Known as the Pacific type it quickly became a popular wheel arrangement for passenger traffic. The 1737 was of this type and was the first of what can safely be said to be the most celebrated single class of Pacific in the United States. The 1737 was completed in May 1914 at the railroad’s Juniata Shops (Altoona, PA). Only after extensive stationary and road tests, lasting two years, was regular production begun. The design was a splendid success –simple, free steaming and powerful – 425 K4’s were built between 1917 and 1928. One thousand ton passenger trains of 13 to 18 cars were handled at 80 mph by these machines and while the design was considered conservative – if not obsolete – during its last years of production, the K4’s proved more capable of handling more difficult operating schedules with the passing years. With the substitution of diesel-electrics following the Second World War, K4’s were assigned to secondary runs or retired; by 1957 all were out of service. Two have been preserved: one resides in the Railroad Museum of Pennsylvania at Strasburg, and the other is undergoing restoration at Steamtown National Historic Site.
The original order of K4’s were fitted with superheaters, and Walschaert valve gears but few other modern appliances. Later orders included power reverses and automatic stokers but feed water heaters and boosters were considered unnecessary and never applied. An interesting feature of the K4 and many other Pennsylvania Railroad locomotives was the Belpaire firebox; this is evident by the long, squarish hump at the rear of the boiler near the cab. The design was developed in 1860 by Alfred Belpaire of the Belgian State Railways but was little used in this country until after 1890. The chief advantage of this firebox is that the crown sheet and the top outer wrapper of the boiler are parallel, thus permitting easy staying between the two sheets.
The leading dimensions of the 1737 were: cylinders 27” x 28”, wheels 80” in diameter, weight 152 ½ tons (engine), 84 tons (tender), heating surface 4035 sq. ft; tractive force 41,845lbs. The tender carried 12 ½ tons of coal and 7000 gallons of water.
Model Photo: 61,707-A
Currently on loan
Object Name
Model, Locomotive
date made
ca 1967
used date
Severn-Lamb Ltd.
place made
United Kingdom: England, Stratford-upon-Avon
Associated Place
United States: Pennsylvania
Physical Description
brass (part material)
alumnium (part material)
steel (part material)
paint (part material)
overall: 7 1/2 in x 5 1/4 in x 41 in; 19.05 cm x 13.335 cm x 104.14 cm
ID Number
catalog number
accession number
See more items in
Work and Industry: Transportation, Railroad
America on the Move
Data Source
National Museum of American History
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