General GWR Castle Discussions

The Bristolian thread elsewhere has become a little clogged up with general Castle posts, so hopefully we can continue the chat here.

So to start things off...

The catalogue description for the numberplate from 5001 http://www.sheffieldrailwayana.co.uk/catalogues/1003/main.htm suggests that the loco was fitted with 6'6" (I assume King) wheels for a short period in 1931. I had never heard this before, does anyone know anything about this or have an idea why it was done?

 

Reference is made to the switch here:
http://www.greatwestern.org.uk/m_in_cas_castle5a.htm
but it also remarks that the switch was only kept for a few weeks so one would assume that it was not successful.

Also have a look here:
http://www.rec-farnborough.org.uk/trivia.htm
and scroll down to the section on '8-wheeled tender' - looks like 5001 was used for a number of experiments.

And here:
http://www.railuk.info/steam/getsteam.php?row_id=2863
which refers to 5001 being used to test ideas for the Kings.

Hope this helps,


Keith

 

This loco wasn't fitted with 6ft 6ins wheels as such, what actually happened was that it was probaly fitted with a set of new standard Castle tyres which were turned down below the normal minimum tyre depth to 6ft 6ins dia in order to test what the difference in performance would be if such wheels were fitted to the proposed new loco's which of course eventually turned up as the Kings with 6ft 6ins wheels. The reason new tyres would have been used is to ensure that there were no residual stresses as the tyres were thinner than normally permitted, and would consequently be less likely to break due to over stressing. As you say once the experiment was concluded, standard size tyres were soon re-fitted.

 

Thye problem with this is that it was done in 1931 (so the records suggest), 4 years after the first King appered, so no idea what it was all about! Perhaps Collett was looking at another 4-6-0 design??

 

It could have been one of those "accounting" ideas to create a "new" class of locomotive by merely altering the driving wheel size plus a couple of other tweaks to justify government capital funding. Otherwise, maybe a proposal aimed at standardising wheel diameters to make life easier in the shops. We can but speculate.

 

I have dug out W.A. Tuplin's book 'Great Western Power'. In which he say's that in the early 1930's the idea of an enlarged Castle was floated at Swindon.
Although he doesn't know for sure how much was commited to paper he says the idea was to have an enlarged boiler of 6'3" diameter with a 35 sq ft grate and 180lb pressure.
Some of the other dimensions he gives are.....outside cylinders 16"x26", inside cylinders 18 1/2"x30". Driving wheels 6'8 1/2" diameter. Overall height 13'1".
He says that having boiler pressure at 180lb would have meant the boiler could be built with thinner plates and possibly less stays, thus giving a weight saving of 10 to 15%.
The Nominal Tractive Effort of the engine would be 32,000lb.
He says himself that it was only a speculative idea but it's worth getting hold of the book just to compare his drawing of the 'super' Castle with that of King George V.

 

What Crewe Hall suggests is exactly what was done: I think its documented in Cook's Swindon Steam. I submit that the smart money should be that the auction catalogue has the date wrong. Certainly there would have been no need for another experiment as all the data was known from the experiemnt that led to the King class' wheel size.

 

Indeed ! Cook records that 5002 Ludlow Castle (NOT 5001 Llandovery Castle as claimed) was fitted with 6ft 6in diameter wheels for a short period before the King design was finalised. This was done by fitting brand new tyres (3in thick) and then turning them down by 1.25in, leaving them slightly below the scrapping size (which was 2in at that time). It ran like this for only a short time and performance was quite satisfactory.

David

 

Hmmm... sounds a bit like one of Mr Tuplin's regular forays into La-La Land if you ask me!

 

I think I would go with Kenneth Cook rather than an auction catalogue compiled by some semi informed catalogue compiler!

You will also find somewhere in Cook's writings comments regarding what has been alluded to earlier in this thread as the "Super Castle". It was actually a proposal by Stanier and Hawksworth (I think) for a compound Castle, which apparently got very short shrift from Collett when they presented the idea to him. Hence the disparity between inside and outside cylinder diameters quoted from Tuplin.

 

Oh yes, compound Castle... they were in and out of the big man's office within a few minutes if I remember rightly? Bit of a non-event to say the least!

 

The relevant details are in the R.C.T.S. book The Locomotives of the Great Western Railway part 8 Modern Passenger Classes page H15 in which it states "From December 1926 to March 1928 No 5001 ran with 6ft 6in coupled wheels for trials in connection with the introduction of the Kings. A second hand set of tyres was specially turned down for the purpose".
bizerba

 

With his training in marine engineering I imagine it was one subject on which CBCs knowledge greatly exceeded that of his subordinates. I wonder, without much knowledge to back me up, whether the reason why compounding, so successful in marine engines, was comparitively unsuccessful on railways was the loading gauge problem... I found a reference giving the dimensions of a triple expansion marine engine from 1888 as being:-
12" x 26"
20" x 26"
32" x 26"
I didn't in a quick sweb search find much to suggest how typical that is, but it suggests that fitting in decent size LP cylinders could be a bit of a problem...

 

Compound engines on ships tend to be started and run at a constant speed/cutoff for far longer periods than railway engines, I believe that this is part of the reason why they were not used much on UK railways. There was an article that covered it in Model Engineer recently, from memory I think the authour concluded that in the UK it was not worth while doing.