PDF - Instructions:
UP Class 4000 “BIG BOY”



The item offered here is a digital assembly instruction in PDF file format. There are no construction elements included in the offer! The image is a digitally created image and is only intended to represent the finished product.

Number of stones: 1,946
Level of difficulty: Hard
Age recommendation: 18+
Designed by: Fabian

In addition to the parts list, you will need the following parts in the colour black:

8x L-wheels 30,4mm (coming soon)
8x L-wheels 30.4mm without flange (coming soon)

This time, the focus of the design was completely on the appearance, because with a locomotive of this length and with such a wheel arrangement, cornering looks strange anyway. That's why there is also a beautiful display stand that emphasises the look of the locomotive on your shelf.

The Union Pacific Railroad (UP) Class 4000, known as the Big Boy, is the UP's largest and most powerful steam locomotive series and one of the largest and most powerful in the world.

A total of 25 examples of the type were built by the American Locomotive Company (ALCO), 20 in 1941 and five in 1944. The machine was designed by a team led by Otto Jabelmann, under whose responsibility the predecessor class 3900 (manufacturer's designation Challenger with the axle arrangement (2'C)C2'), which was nevertheless still built in parallel, had already been created. An unknown employee of the ALCO works came up with the name Big Boy, which he wrote in chalk on the smokebox. The designation quickly became established for the UP Class 4000 locomotives.

The locomotives were specially designed by the Union Pacific Railroad for use in front of goods trains in the Rocky Mountains in order to avoid the labour-intensive use of lead and push locomotives on the gradient sections over the Continental Divide. The most difficult section on the Union Pacific's transcontinental route was a long grade over Sherman Hill in Albany County (Wyoming) south of the Ames Monument with a maximum gradient of 15.5 ‰. The new locomotives were to haul trains of 3600 short tons (about 3300 t) over this gradient without a prestressing or sliding locomotive, but were also to be fast enough to run the entire distance between Cheyenne (Wyoming) and Ogden (Utah) without changing locomotives.

The required performance data resulted in an articulated locomotive with the wheel arrangement (2'D)D2' h4 (Whyte notation: 4-8-8-4). No other locomotive was ever built with this axle arrangement. Like many of the newer US articulated locomotives, the Big Boys were not Mallet locomotives in the true sense of the word, because the steam engines worked with simple steam expansion without compound action. In American, this type of construction is therefore called simple articulated. The frames of both engines were integral cast frames including the cylinders, the drag axles were mounted in a delta drag frame which was also cast. The axle and rod bearings were roller bearings.

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