Nunney Castle

Oh indeed it was - the GWR General appendix to the rule book has no less than 6 pages on restrictions on various types of carriage, both within the GWR system and elsewhere. I do think they were slightly less precise about it though. There are some LNER documents at Kew discussing standardising loading gauge dimensions and rules for what stock could be used on which routes, including a letter from one division objecting to the proposals on the grounds that they would prohibit certain stock from running on routes where it had been in use for many years.

 

With regard to the aforementioned video, it seems that Nunney is being rebuilt with a three-row superheater! At about 40mins.

 

You mean like 7027 was?
Ray.

 

7027 was a single-chimney Castle.

 

Oops!

 

Does that mean a boiler swap,then? If so, what with?

 

Possibly not a boiler swap, but changing how many rows the superheater has requires at a minimum a new front tube plate, and a new inner firebox tube plate, not to mention requiring casting of a new superheater header (if one isn't available from elsewhere) which is a particularly complicated casting to make. So it is not a small modification.

Tom

 

I think I remember reading that article too. I may be wrong but I think the header was coming from 7027

 

If that is correct, it will interesting to see what 4709 has! A row of empty flues?

 

They would have to put something in the flues, otherwise it won't steam very well. It might be more sensible to obtain a superheater header compatible with the boiler?

 

Is superheating advantageus on less than 10km trips in Preservation Land?

 

Not particularly - but blanking off the superheater in a boiler that was designed to be superheated gives you the worst of all worlds, since you lose heating surface by having reduced number of tubes, and the draughting gets mucked up because all the designed ratios get disrupted, and the hot gases preferentially go through the flues (without much surface area) rather than the tubes.

Tom

 

OK but if firebox frontplate of cupper has to be changed anyway?
Smokebox tube plate is made of cheap steel.
Chapelon argued that some % of the cylinder efficiency loss, when not superheating ,can be recovered by more small tubes giving better boiler efficiency..

 

Is

Is Nunney Castle expected to do many trips less than 10Km then?

 

I think that was aimed at the Owl rather than Nunny.

 

I would think that 5029s overhaul had been planned, specified and started before the situation with 7027 changed at the GCR..... with the benefit of hindsight things might have been done differently.....