British Rail Class 55 - Performance

Performance

The introduction of the Deltics was a step change in locomotive performance on the East Coast Main Line. The recently introduced class 40 diesels had an absolute maximum drawbar horsepower of 1450 and this could be exceeded by a Pacific steam locomotive if worked hard. On one of O. S. Nock's first Deltic runs (the down Heart of Midlothian loaded to 13 coaches 530 tons gross) he states "once the tail of the train was over the 60 mph restriction the throttle was opened to the full, and the surge forward could be felt in the cab. Never previously had I felt a positive thrust in my back when in the second man's seat!" Nock went on to estimate that at 80 mph the locomotive was producing about 2750 drawbar horsepower. As early as 1963 Deltics were recorded exceeding 100 mph, Nock recording 100 mph for 16 miles south of Thirsk with a maximum of 104 mph, he went on to say that such speeds in 1963 were "terrific".

By the mid 1960s the Deltic hauled Flying Scotsman was achieving a 5 hour 55 minute time from King's Cross to Edinburgh with one stop at Newcastle and this was the fastest ever timing, beating the pre war A4 hauled "Coronation" service's 6 hours, and without the priority over other traffic accorded to the earlier LNER train. As the East Coast Main Line was upgraded times dropped still further and by the mid 1970s the Flying Scotsman was reaching Edinburgh in 5 hours 30 minutes, still with one stop at Newcastle.

The ultimate Deltic performance came on 2 February 1978 with a run on the 07:25 from Newcastle to King's Cross. In some respects the run was set up (the driver was about to retire) but the speeds were record breaking. The locomotive was 55 008 The Green Howards, it was hauling 10 coaches (343 tons gross) and on the leg from York to London it achieved a timing of 137 min 15 sec. This included various signal stops and other enforced speed reductions, the nett time is estimated at 115 min 45 sec, an average of 97 mph start to stop. The train achieved 113 mph on the flat between Darlington and York, 114 mph at Offord and 125 mph whilst descending Stoke bank.

The Railway Performance Society estimate that on modern infrastructure (the Selby diversion etc.) a realistic Deltic hauled schedule from King's Cross to Edinburgh would be around 4 hours 57 minutes (a theoretical unchecked run being around 4 hours 40 minutes). This would be for a train of 11 coaches and include a stop at Newcastle, the latter city being reached in a scheduled 3 hours 6 minutes.