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The LNER W1 4-6-4 and Water Tube Boilers

An interest in steam rail traction began at school, and led to an apprenticeship as a loco fitter, a not very good one from which the chief lesson was how not to design things, the interests of those having to work on them being apparently ignored. This was followed, after two wasted years in National Service, by a year or so in Doncaster D.O. and a few weeks at Rugby Testing Station. It was then that the announcement came of the end of steam, on a miserable, murky November day, and interest suddenly waned and, for this and other reasons, came a parting with B.R. and involvement in other fields of engineering design.

More than half a century later interest was re-awakened by the discovery of the Tornado project, in which a modest financial involvement followed largely due to memories of two lively footplate rides on one of the originals from Darlington to Grantham, and then some reading on other L.N.E.R. loco matters, including the ill-fated W1. From this some speculation was aroused by reading, on p75 of William Brown’s book ‘Hush Hush’, that a diagram had been found of a K3 fitted with a water tube boiler, and the question was, why was this drawn if the grandiose W1 had been decided upon? One answer just might be that this was Gresley’s original idea, which would make engineering sense as he was a cautious designer unlikely to try something completely new and experimental in a way that would draw much public attention and, in the event of its failure, scorn. Other factors at the time were HNG’s domestic problems, the enthusiastic publicity department of the L.N.E.R., and the presence on his staff of one Oliver Bulleid. As his activities on the S.R. later showed, this gentleman could be very persuasive and was imaginative, with many novel ideas that had variable success. So the C.M.E. had to take full responsibility, but is it fair to assume that the W1 was entirely HNG’s design? Although the date on the K3 drawing is later than the building of the W1 that is no guarantee that it was not drawn earlier, and shelved.

More detailed study of what has been obtainable on the W1 suggests to this writer that Bulleid’s footprints are all over it. Ingenious but unnecessary items like the air supply to the ashpan for example and the layout of the tubing that added to a complexity that was not really needed merely added to the cost but didn’t improve performance. At about the same time Sentinel successfully used the more simple Woolnough design on locos for Columbia that produced steam at 550psi. And this, incidentally, was for a two bogie design that preceded the Bulleid Leader.

It is often stated that water tube boilers have been used on locos in other countries, in the U.S.A. especially, but on investigation they turn out to be a combination of water tube firebox and fire tube barrel on the lines of the Brotan-Defner. This has much merit and has been successful where economy of coal usage has been desirable, but high pressures were not possible unless there was much added weight as in one U.S. case, where route availability was severely compromised. But the case for pure water tube includes the opportunity to use a much higher pressure, which in theory at least can lead to fuel and water economy. And with modern welding techniques a much more water tight assembly is possible, whereas the W1 for example still needed tubes to be expanded into place and that required access for maintenance.

So an attempt has been made to design in broad terms a water tube boiler to take the place of an L.N.E.R. 100A type, though not totally within the profile of one, it being thought desirable to use all the space available within the loading gauge. This has been merely an exercise in feasibility, and would appear to be not unreasonable, though details of heating surface area have not yet been attempted as just how these should compare with those of a firetube type for the same steaming rate is not known. More knowledgeable help would be appreciated there.

Another difference from the normal was the use of compounding, which with piston valves is considered necessary due, presumably, to obtaining any precise control over the cutoff, but would the use of gear driven poppet valves make this easier is a question to which an answer would be welcome. But that subject may be better treated separately.