Union Pacific 4-8-8-4 Big Boy Live Steam Locomotive

An accurate scale live steam model of the Union Pacific 4-8-8-4 Big Boy can be built using our Challenger castings. The Big Boy is a logical extension of our Challenger model design, as demonstrated by these photographs. 

"I have now had the opportunity to look through the castings. They are absolutely superb. What an achievement to have designed such a complex engine. The tender bed is a work of art even before it is machined. I realized it was a big engine but seeing the parts makes my estimation too conservative! Cannot wait to get started!"
— M.M., Aberdeenshire, Scotland

Please note that we are modeling the Union Pacific 4-6-6-4 Challenger and that we are NOT modeling the Union Pacific 4-8-8-4 Big Boy. We have NOT performed the "reengineering" that is required in order to model the Big Boy.

Nevertheless, the following photos show that one of our customers has successfully used our Challenger castings and our 14-wheel centipede tender castings to build an accurate scale model of the Union Pacific Big Boy.

Proud builder Floyd Epperson is enjoying visiting different club tracks with his newly completed Big Boy...

...and showing how many cars and passengers it is capable of pulling.

Historical Info

From a historical standpoint, the designs for the full size UP 4-6-6-4 Challenger and the UP 4-8-8-4 Big Boy were very, very similar since both locomotive types were designed by Union Pacific Vice President Otto Jabelmann and both types were built at the same time in the same shops by ALCO. Therefore, the same similarity would also exist between a model of Challenger and a model of a Big Boy.

Stretching the Design

Our Big Boy customers are "stretching" our design for our Challenger model into their own design for their Big Boy models.

Interested in building your own Big Boy? Contact us — we’d love to hear from you.