The rear suporting axle of a 'pacific'4-6-2 wheel arranagement is known as a trailing truck.
The trailing truck currently fitted to 21c11/35011 General Steam Navigation is different to the ones in service on other preserved Merchant Navy pacifics. When the first twenty Merchant Navy pacifics, including 21c11/35011, were built they were all fitted with a cast trailing truck.
These original trucks with their characteristic arched shaped castings were originally only fitted with an asbestos cloth sheeting to protect the spring beam. This was not in practice very effective and therefore after the war a metal cover was fitted.
The final ten starting with 21c21 New Zealand Line entered service with a new lighter fabricated design that still matched the performance and mounting arrangements of the original cast design to ensure interoperability.
The composite image top right shows both the original cast style arrangement and the later fabricated arrangment.
Research has shown that our 35011 was fitted with a fabricated truck when she was undergoing “Heavy Intermediate” repairs at Eastleigh between 25/01/55 and 19/02/55. The switching of the trailing trucks, like other components, during overhauls was not uncommon with 35002, 3, 4, 15, 17 and 19 also known to be fitted with a fabricated trailing truck design during their careers and likewise those of the last ten of the class originally fitted with a fabricated truck were later fitted with cast trucks including 35027 and 35028 that carry them to this day within preservation.
The only fabricated trailing truck for a Merchant Navy that survives is currently on 21c11/35011and this will give her another unique feature when compared to her preserved sisters.
The image bottom right shows the assembled truck on 21c11/35011 from acquired and new components.