LNER Class W1

The LNER W1 No. 10000 (also known as the 'Hush-Hush' due to its secrecy) was an experimental steam locomotive fitted with a high pressure water-tube boiler that had been used with great success in marine applications. The boiler was designed by Harold Yarrow and constructed by the engineers and boilermakers Yarrow & Company in Glasgow. It had a working pressure of 450 psi (30.6 atm) as opposed to the 180 psi (12 atm) of the current Gresley A1 locomotive. This remarkable apparatus was paired with a Gresley pacific chassis with an additional axle to accommodate the extra length. This resulted in a 4-6-4 wheel arrangement, making No. 10000 the only standard gauge 4-6-4 tender engine to run on a British Railway. The high pressure necessitated compound expansion; steam being supplied to the two 12"x26" (304.8 mm x 660 mm) high-pressure inside cylinders and then fed into two larger 20"x26" (508 mm x 660 mm) low-pressure outside cylinders before going to exhaust. High-pressure cylinder diameter was subsequently reduced to 10" (254 mm). Gresley incorporated an ingenious unique system for giving independent cutoff to the high-pressure cylinders using only two sets of Walschaerts valve gear derived from the outside cranks on the Von Borries principle [van Riemsdijk, John (1994). Compound Locomotives. Penryn, UK: Atlantic Transport Publishers ] . and using an inside half-length expansion link [Brown, F.A.S: Nigel Gresley Locomotive Engineer (Ian Allan, London, U.K., 1961) p. 104 and fold-out drawing] .

The locomotive was completed at Darlington Works in 1929.

The locomotive had a corridor tender and ran non-stop London-Edinburgh services to time in 1930; nevertheless steaming was relatively poor during test runs, and in spite of a number of modifications initially to the exhaust, boiler performance never reached the standards of an equivalent firetube boiler. A problem never fully solved was air leakage into the casing [Brown op. cit. p.106] .

When it was deemed that no further progress could be made, the locomotive was taken to Doncaster Works in 1936 and rebuilt with a conventional boiler and three simple expansion cylinders on the normal Gresley layout. A modified A4 boiler was fitted which had 50 sq ft (4.6m²) of grate area and 20" (508 mm) diameter cylinders. The valves were considered undersized for the large cylinder diameter and this somewhat limited the speed capabilities of the engine. Its haulage capacity was nonetheless appreciated.

No. 10000 never carried a name; plans in 1929 to call it "British Enterprise" were dropped, although nameplates had already been cast; a later plan to call it 'Pegasus' did not come to fruition eitherFact|date=December 2007. Its nickname in the early form was the "Galloping Sausage". From 1948 under British Railways it was renumbered 60700.

On 1st September 1955 60700 had just departed from Peterborough when the front bogie frame broke at 20 mph. The locomotive derailed at Westwood Junction, but the quick reaction of the driver stopped the train, upright, just short of Westwood Bridge. The engine however fell onto its left hand side under one of the arches. It was recovered and sent to Doncaster for repairs on an accommodation bogieFact|date=December 2007. 60700 was withdrawn on 1st June 1959 and broken up in Doncaster Works.

External links

* [http://www.lner.info/locos/W/w1.shtml LNER encyclopedia]

Notes