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LNER W1 10000 "Hush Hush" 4-6-2-2

LNER W1 No 10000 Hush Hush in O gauge available from stock or larger  Gauge 1 version  - pictured below.

01

This article has been contributed by William Brown - author of the book detailed below which we give with every purchase.

The LNER W1 No. 10000 also known as the 'Hush-Hush' possibly due to its secrecy was an experimental steam locomotive fitted with an extra high pressure water-tube boiler. Nigel Gresley was aware of the results of using extra high-pressure steam and so in 1924 he and Harold Yarrow of shipyard & boilermakers Yarrow & Company of Glasgow designed a suitable water tube boiler for a railway locomotive, based on Yarrow's design. The conventional boiler was at its limit whereas the water tube was a long way from it. (4500 psi today)

Boiler

The boiler was the usual Yarrow design. It has been described as an evolution of the Brotan-Deffner water-tube firebox, with the firebox extended to become the entire boiler to eliminate the problems with the interface between water tube firebox and conventional barrel.

The boiler was two marine Yarrow boilers, joined end to end. Both had the usual Yarrow triangular arrangement of a central large steam drum above two separated water drums, linked by multiple rows of slightly curved tubes. The rearward "firebox" area was wide and spanned the frames, placing the water drums within 3 inchesof the limits of the loading gauge. The forward "boiler" region was narrow-set, with its water drums placed between the frames. The space outboard of the forward set of tubes formed a pair of exhaust flues leading forwards but later housed the reheaters. Longitudinal superheater tubes of the conventional kind were placed between the forward steam generating tubes from the outset. A large space outside the flue walls but inside the boiler casing was used as an air duct from the air inlets, a rectangular intake in front of the smokebox door and two others set lower at either side, which had the effect of both pre-heating the combustion air and also cooling the outer casing. The third area forwards contained superheater headers, the regulators and the smokebox. The external boiler casing remained at much the same width throughout, giving an overall triangular, but curved, appearance. The lower edge of each section stepped upwards, and was obvious externally.

Working pressure was to be 350 pounds per square inch as opposed to the 180 pounds per square inch of the contemporary Gresley A1 locomotives. The low pressure steam chest was set to blow off at 180 pounds per square inch. The working pressure had been raised to 450 pounds per square inch at about the same time as the Pacifics were raised to 220 pounds per square inch and it was at this pressure the locomotive became hardware. North Road works had forgotten to change the low pressure steam chest blow off settings to compensate, although until the problem with the manifold had been rectified to release the boiler to work as designed, it did not matter. It was finally raised to 480 pounds per squre inch for the double blastpipe tests, the low pressure correctly blowing off at 240 pounds per squre inch.

The heavy forgings for the main drums were manufactured in Sheffield by John Brown. The boiler was constructed and fitted to the frames by Yarrow in Glasgow, involving the rolling chassis being carried over the LMS, carefully sheeted over to avoid too close an inspection by a rival railway company. This chassis was a 4-2-2-4 at this point, as the centre drivers and rods had not yet been fitted. The first Yarrow works photographs, with the boiler cladding in grey, were taken in Glasgow, with a wooden dummy centre driver and coupling rod added for the photo.

02

Motion

This locomotive was to be on a Gresley Pacific 4-6-2 chassis, but ultimately an additional axle was added to accommodate the extra length of the water tube boiler. 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.

In UIC notation this wheel arrangement could be described as a 2 C1 1 (or more fully, 2 C1 1 h4vS) as the two trailing axles were independent, rather than a four wheeled bogie as for those leading. The forward axle was similar to that of the pacifics, having outside frames and Cartazzi axleboxes. The rear axle was an inside-framed Bissel truck, pivoted ahead of the leading axle.

The extra 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) to simulate a single cylinder, a three cylinder compound being Gresleys original intention before being put off in a meeting with the LMS. After this experiment the cylinders reverted to 12". Gresley incorporated an ingenious 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 and using an inside half-length expansion link to achieve independent cut off between high and low pressures.

03
In service

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 in spite of failing auxilliaries, including, vitally, boiler feed. The neat manifold arrangement, of which Nigel Gresley was so proud, failed to work, lacking steam supply, due entirely to the feed tube size. This was rectified a few silent months after the previously indisposed injector supplier discovered the fault and informed Nigel. The injectors got an independent supply in 1931 and  from then on the boiler exceeded expectations, although the cab got very hot as a result.

04
Rebuilding

When it was deemed that no further progress could be made in the short term, with the sucess of Silver Link and the onset of the war, the locomotive was taken to Doncaster Works in 1936 and rebuilt with a P2 boiler with amended tube arrangement and three simple expansion cylinders on the normal Gresley layout.The boiler fitted 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 the highest of any passenger locomotive ever to run on British Railways.

No. 10000 never carried a name, although it did carry small works plates on the smoke deflectors bearing the number 10000. In its early form, it was known unofficially as the Hush-Hush as a result of the initial secrecy surrounding the project, although it could have been due to the noise the locomotive made, possibly both, and also the "Galloping Sausage" as a result of its boiler shape. Plans in 1929 to name the original engine British Enterprise were dropped, although nameplates had already been cast; a 1951 plan to name the rebuilt engine Pegasus did not come to fruition either. From 1948 under British Railways it was renumbered 60700.

05

On 1 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 the signal box. The engine however fell onto its side. It was recovered and sent to Doncaster for repairs. The bogie had failed due to a weld repair. It was a B17 Bogie and it was forbidden to weld repair any waisted frames an these locomotive bogies. There was an urgent need for the locomotive and this instruction was missed in the haste. The machine did return to traffic until all remaining non standard locomotives were condemned.

06

60700 was withdrawn on 1 June 1959 and broken up in Doncaster Works.

Purchasers also get this book "Hush-Hush, The Story of LNER 10000"
by William Brown and published by Kestrel (normal price £19.95) free of charge

 book
book cover :HUSH-HUSH The Story of LNER 10000 William Brown

Footnote from William.
The Union of South Africa, 60009 runs today with the tender that was behind Hush Hush for the whole time it was numbered 10000. The W1 got another tender, by coincidence, when it became 60700. The original tender was in store when 60009 was purchased for preservation, the purchaser chose the tender in the best condition to go with it, and the one ex 10000 was the one.

Please contact Lawrie for availability and prices either by emailing lawrie@loveless.co.uk or phoning 01423 712446


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