7027 Thornbury Castle

That a big engine doesnt have to be a 4-6-0, and that big green engines look great... what ? you already knew that ?

 

That's true but to do that means changing both tubeplates! They are not going to do that if they are trying to save money.

 

No no, @GWR4707 'Manorbier Star' with a No 1 boiler because 'it could've happened'...!

 

You are misquoting me. 'Too hard to do/too expensive' does not equal 'not a quick and cheap repair'!

 

I appreciate that; I’m simply correcting the statement that adding more superheater flues increases the heating surface; it does the opposite.

Tom

 

I didn't say that. I was assuming that they would keep 21 flues tubes and only occupy 4 or 6. That would give a lower heating surface than original, as I said.

 

Or to Viscount Churchill (pre-rebuild, of course). After all, there's already a Star in existence, but there isn't a Bear...

 

An interesting idea, one row of 7 maybe and then dummy elements better for heritage railways ?
Thinking best left as is for mainline but the original 47xx lubrication circuit not intended for higher superheat...

 

I hesitate to step back into the maelstrom of misinformation swirling about in this thread - but what the hell...

• The numbers quoted are off with the wrong particulars used in comparison with others. For the record, the standard no8 in early form had 14 superheater flues in 2 rows with 6 elements per flue for a total of 263 square feet of superheater area. Later forms of the boiler had 3 (eventually 4) rows of superheater flues (i.e.21 or 28) with 4 elements per flue. That from 7027 has 3 rows which gives a total of 313 square feet of superheat. I suspect that these are the source of the numbers quoted. A standard number 7 on a 47xx has 288 square feet of superheat. i.e. not all that far from that from 7027. Certainly not enough to even think about altering the pressure.
• There is no need for compensating changes to make up for changes in cylinder bore/stroke. The original intent of using a cylinder block from one of the Barry10 28xxs was dropped in favour of new cylinders modified to meet the NR loading gauge requirements. These have already been cast and their fit into the chassis is pending.
• One of the quoted attractions of the boiler was that the few inches smaller diameter alleviates the problem of boiler fittings in the latter respect and means less modifications to meet the loading gauge. The copper firebox when all suppliers of a new boiler would be talking of a steel inner box, adds to the attraction.

I remain a bit on the fence with this overall. The purist says its unwise, the pragmatist says not.

 

steel vs copper firebox isn't straight foreword, the staying would need to be different

 

I'm not blaming Wikipedia but they've done the same as you, mixing up elements and units. Wikipedia have correctly used the term element in the case of the Castle:

https://en.wikipedia.org/wiki/GWR_4073_Class

and incorrectly in the case of the 4700:

https://en.wikipedia.org/wiki/GWR_4700_Class

Look on the RHS.

A unit is one straight length of tube of an element, an element is the whole assembly. So one element per flue tube. It seems, with further research, that a no 7 boiler had two rows of flues, not one. So I stand corrected.

I didn't advocate a higher pressure boiler or changes in cylinder stroke/bore.

The statement 'The copper firebox when all suppliers of a new boiler would be talking of a steel inner box, adds to the attraction' is almost certainly not true. HBSS have already made a copper firebox for 45551. The statement was most likely used to try to justify the purchase.

 

Have I dreamt the following.....

The owners of 44901 at Berkley sold their boiler to Ian Riley, with the belief that it was life expired and they had lined up an 8F boiler from Turkey?

I am sure they sold the boiler and 901 certainly doesn't have a boiler on it. Mr Riley intended to use it as a spare and have one overhauled at all times to increase the availability of his fleet.

Did I dream/imagine all of the above?

 

No, that's correct. Quite why they thought selling a repairable boiler and buying an unknown one to bodge to fit was a good idea, we'll probably never know. Oh, any parallels with a certain 47xx?

 

That wouldn't work as the combustion gases will take the path of least resistance i.e. through the empty superheater flues rather than the firetubes. Steam production would be drastically reduced as proved when GNR 251 had to be dragged most of the way by its elder sister 990.
Ray.

 

80135 on the NYMR is due to receive a new copper firebox before too long, when work resumes on it.

 

Correct, and he also got the cylinders from 48518.
Ray.

 

The biggest mistake they seem to have made was not checking that there was an 8F boiler available to buy, before they sold their Black 5 version!. Now, they seem to have ended up with neither!

 

Turning a Hall into a Saint was not "preservation" but it was entirely consistent with Didcot's remit as a museum of all things GWR (and successors). It illustrates both the beginning of a long series of locomotive designs and the virtues of standardisation of components. Using major parts of a Castle to help build a 4700 and a Star would likewise not be "preservation", but has anyone claimed that it would be?* Whether it is consistent with Didcot's remit, or whether the differences between the Castle's components and the correct ones for a 4700 and a Star are great enough to invalidate the rebuilds, is a matter of opinion. (But, for the record, I have been persuaded by the arguments on here that using Thornbury's components is a poor idea.)

*other than by discussion on a "preservation" forum, which in practice is somewhat broader than that in scope

True!

 

Agreed. They would have to occupy all the flue tubes. Most (all?) pannier tanks have two unoccupied flue tubes. I'm not sure whether this was a hangover from superheating or to add strength to the top corners.