Thompson Pacific locos of the LNER

The London and North Eastern Railway Class A2/2 was a class of six 4-6-2 steam locomotives rebuilt by Edward Thompson in 1943 and 1944 from his predecessor’s P2 Class of 2-8-2 express passenger locomotives. The rebuilds were not particularly successful and all were withdrawn and scrapped between 1959 and 1961.

On taking up office as Chief Mechanical Engineer of the London and North Eastern Railway in April 1941, Edward Thompson proposed an unstreamlined mixed traffic version of Sir Nigel Gresley’s A4 class pacifics with 6 ft 2 in (1.880 m) driving wheels, but new construction would not have been authorised at this time. He therefore rebuilt the six of his predecessor P2 Class of 2-8-2 express passenger as pacific locomotives to try out his own thoughts on their design. The P2 Class 2-8-2 had been built between 1934 and 1936 for service between Edinburgh and Aberdeen and had proved to be powerful and capable locomotives. However, the long fixed wheelbase was not ideally suited to the winding route, giving rise to maintenance problems on both the track and the locomotives, notably failure of the crank axle. However, O.S. Nock stated that the P2 class 'rode easily and elegantly around the sharpest curves.' In either event, rather than transfer the locomotives to other duties on the East Coast Main Line south of Newcastle, where this would have been less of a problem, Thompson saw this is a chance to try out his own ideas of locomotive design.

The new design steamed well and retained much of the power of the P2's. The reduced weight meant they had a high power to weight ratio, and were good at hauling high speed expresses, although in the opinion of O.S. Nock they 'acquired a particularly bad reputation for wild and unsafe riding at high speed!' However, there were other problems which prevented them from ever making an impact on the east coast main line. The first of these was a lack of adhesion causing wheel slip when starting, which meant that they could not be used on the Edinburgh-Aberdeen line for which they had originally been built. The second problem was that of reliability caused by their having been adapted from quite different locomotives. Both the A2/2 and the subsequent A2/3 suffered badly from frame movement, vibration and loose fittings. Using equal length connecting rods, as well as the divided drive meant that the centre cylinder was much further forward than the outside cylinders. During their lifetime in service Earl Marischal was the only A2/2 to cover over one million miles, 360,907 as a P2 and 673,947 as an A2/2

https://railway-photography.smugmug.../Thompson-A11-Rebuild/Thompson-A22-6050160506


Neil