Union Pacific 'Big Boy' Tender Versions

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The original centipede tenders designed for use with the 1939 Northern class locomotives were slightly smaller and were so successful that the design was adapted for use with all later road engines including the 'late' Challengers and Big Boys. The tender elevation drawing shown above is of a 25-C-1 type built for use with the first production series (4000-4019) of Big Boy locomotive. The drawing below is of a 25-C-4 type used with the second production order (4020-4024) of Big Boys. The primary difference between the two tender types was the amount of water carried, the 25-C-1 carrying 24,000 gallons while the 25-C-4 carried 25,000 gallons, both carried 28 tons of coal. In later service you will find that the two tender types were frequently interchanged between locomotives from the two production orders. You will note the obvious differences in the seam and rivet placement as well as the front equipment compartment configurations. The tender beds were virtually identical.

For the first time to our knowledge, our Big Boy project will provide correct pairings of locomotive and tender types for all road numbers included in our production. there will be early and later service variations included in the production and they will include the appropriate detail not represented in the basic construction elevation drawings shown here. If you are interested in ordering a 'late' version model and want to know what tender it will be assigned, all road numbers will have 25-C-1 tenders except the following which will be paired with 25-C-4 units: 4000, 4002, 4006, 4009 and 4017.