Drift from the 6201 thread

There is an outline drawing of the 4-6-4 in Locomotive Panorama Volume 1 by E S Cox. There are some intesting comment about this, in particular the difficulty of of getting sufficient free gas area through the tube bank. The maximum boiler barrel diameter was to be increased to 6' 10 3/8" to achieve this. Apart from Garratts the largest boiler diameter used in the UK was 6' 5 1/2". I believe steam locos in Britain were reaching the limit of their possible power output because of this limitation

 

Pretty sure it was a few A2's which got sent to Polmadie in maybe 63 but were virtually unused.

 

I wasn't aware of that, but I have a feeling that A1s were tried in the late '40s or early '50s. I will have to dig out the relevant book next time I visit my parents...

 

This gets interesting. A1s 60152, 60160 and 60161 were allocated to Polmadie at various times between 1951 and 1953. They got as far as Crewe on one roster.
A2s 60512, 60522,60524, 60527 and 60535 were allocated to Polmadie from October 1963 until withdrawal at various times during 1965. They did very little work, mostly substituting for failed diesels as far as Carlisle, but 60522 made it to Leeds. All were painted with the yellow stripes in August 1964.

 

Thanks - it is good to have a little more detail on the LMR motive power situation at the time. It also serves as yet another reminder of how that irritating factor, human beings, can spoil a lot of a plans which look very attractive on paper!

 

Ah, you just beat me to it! Thanks

 

...and me! There was at least one recorded instance of a 66A A1 getting as far as Birmingham New Street IIRC

 

Yup I was just looking at the LNER encyclopedia site. Also interestingly 60530 was there at that time and escaped to Dundee Tay Bridge.

 

In the later years of the LMS, the plan was clearly to convert many, probably all, of the 5XP Jubilees and Patriots to 6P Rebuilt Patriot format (or 6P to 7P in BR speak). In fact, only about half the Pats and only 2 Jubes were done.
This would have given the LMS a lot more numerous fleet near the top of the power range - remembering how many 5XP there were (hundreds, as opposed to a couple of dozen Pacifics and a few dozen Scots)
I think the relatively few 7P locos (8P for BR) was a deliberate decision, and was of course helped by the fact that with their greater availability, five Duchesses did the work of six A4s.
In terms of future top end motive power, the LMS plans were evolving through the war years. Both a 4-6-4 and a 4-8-4 were proposed and developed to some extent, but it's not clear whether they ever came close to actually being ordered. Ivatt then worked on his diesel electrics, which, being very successful, would presumably have been built in significant numbers if the LMS had continued as an independent company.
The real answer to the WCML was and had always been electrification, as Hughes proposed back in the mid 1920s... but that had to wait until the 1970s for completion.

 

I'm not sure that's correct. While the Baby Scot boilers were getting on and had problems in the smokebox area, the 5X boilers were relatively new; replacing them with Class 2A boilers would have been expensive as there was no alternative use for those displaced.

The way I heard it, the need for 91 class 6Ps (7P under BR) post war was identified. There were already 71 Scots (including 6170) and the two rebuilt 5SXs, 5735/36, meaning that 18 8Baby Scots would need to be rebuilt, as happened. An alternative theory is also suggested that Riddles vetoed further rebuilds as they would make his Standard Class 6s and 7s, the Clans and Britannias, unnecessary.

 

I think Jenkinson in one book quotes a memo about the idea to rebuild all the 5XPs.
He certainly quotes the 91 class 6P and the logic you mention.
It may be that the others would have been done as and when boilers were due, as you suggest. But there was certainly a plan to rebuild most if not all with the 2A boilers eventually.
As you say, Riddles new designs changed the plans.