The LNER Encyclopedia

19. l am satisfied that the main components of the valve gear of the centre cylinder were in good
order when the engine left Haymarket Shed to work the train. There was no weakness in design or flaw
in the material, and 1 believe the accident occurred because two nuts on the top bolt of the eccentric strap
became unscrewed during the journey. This could not have happened if there had been a properly fitted
split pin through the bolt outside the lock nut, and even an undersized one should have checked the
unscrewing of this nut. Furthermore, a properly fitted pin could not have fallen out on the journey, though
an undersized one might have done so if the legs had not been sufficiently splayed. I conclude therefore
that there was not a properly fitted split pin in the top bolt of the eccentric strap when the engine was
examined at Haymarket Shed before the trip, though there may have been an undersized one which
subsequently fell out.

20. It was suggested to me that the stripping of the thread of the top bolt might have been caused
by excessive pressure which forced off the nuts and sheued the split pin. However, tensile tests to
destruction with similar bolts with only one nut caused the shank to elongate and break under a pull of
48 tons; the threads were undamaged after the tests and the nut still free to turn. A properly designed
thread and nut should of course produce this result, which disproves the suggestion unless the threads of
the bolt and nuts had been badly worn. As the nuts were lost and the bolt much damaged and rubbed,
the wear in the threads before the accident occurred could not be assessed, but I have no reason to believe
that the bolt and nuts would have been allowed to get into so unserviceable a state.

REMARKS

21. I visited Haymarket Shed shortly after the accident in order to see how an examining fitter made
his inspection of an engine. I found that though the inspection seemed thorough, the attitude towards
split pins was far from meticulous. Undersized split pins were not booked and I was told that they were
sometimes fitted because a lock nut masked the split pin'hole after adjustment or repair. I found no evidence
that the supervising staff insisted on the proper practice of nuts being fitted so as to bring the face level
with the edge of the split pin hole, either by using a washer or turning or filing down the nut.

22. A derailment at Brownhill Junction, Dalry, on 17th September, was also caused by the falling
out of an undersized split pin fitted at Kingmoor Shed during the adjustment of tender brake gear, and
carelessness in the fitting of split pins was responsible for three accidents on British Railways in 1952.
Although only 2 - 3 per cent of the accidents reported to the Minister each year are attributable to locomotive
defects, it may he desirable to impress on all concerned once again that inattention to detail in
fitting and examining work at the sheds may have very serious consequences.

23. It happened that this derailment occurred at the same facing connection as the one on the 26th
October, 1947, but the cause was different. The less serious consequences on this occasion may be ascribed
to the fact that the train was not diverted from a straight path and the coaches therefore maintained their
alignment.