flying scotsman123 wrote:...I am very much not an expert in this, but I have been reading with some interest the discussions between those who are, who seem to have come to the opposite conclusion, backed up by original LNER data here.
I promise you the guy behind that analysis is not an expert of any sort.
To get the story straight.
The P2s were a problem class, and needed a lot more development to iron out their deficiencies, for which there was not the resource in wartime. Probably the best thing to have done with them was base them at Doncaster where works attention was more readily available, and use them on the ex-GN route with its easy curvature to handle the large wartime loads.
Thompson's rebuilding produced a better machine in terms of availability. However not so good as the previously constructed pacifics, and with a reduction in tractive capability compared to the P2. Same again with the four last V2s ordered, completed as A2 pacifics, and the A1/1 rebuild ; inferior to the A3 and A4 pacific designs in performance and availability and there's ample evidence for that. The Thompson pacifics ran smaller mileages, ended up based in secondary locations rather than principal depots, and had greater repair cost than the previous pacifics, and went to the scrapper earlier ahead of much older locos.
There was nothing wrong with the principal components of the Thompson pacifics, they were all Doncaster standard parts as developed under Gresley, just the arrangement of the wheelbase which Thompson required because he had an obsession for equal length connecting rods above all other engine layout considerations. Peppercorn arranged the same components on the established conventional wheelbase layout, and these performed perfectly well; and in the case of the A1 were probably the most reliable express traction BR had.
Thompson got it badly wrong in short when it came to his pacifics.
With a new P2 being built and a lot more experience and analytical tools available, it will be interesting to see just what emerges.