LNER Class W1
Encyclopedia
The LNER W1 No. 10000 was an experimental steam locomotive
Steam locomotive
A steam locomotive is a railway locomotive that produces its power through a steam engine. These locomotives are fueled by burning some combustible material, usually coal, wood or oil, to produce steam in a boiler, which drives the steam engine...

 fitted with a high pressure water-tube boiler
Water-tube boiler
A water tube boiler is a type of boiler in which water circulates in tubes heated externally by the fire. Fuel is burned inside the furnace, creating hot gas which heats water in the steam-generating tubes...

. Nigel Gresley was impressed by the results of using high-pressure steam in marine applications and so in 1924 he approached Harold Yarrow of shipyard & boilermakers Yarrow & Company of Glasgow to design a suitable boiler for a railway locomotive, based on Yarrow's design
Yarrow boiler
Yarrow boilers are an important class of high-pressure water-tube boilers. They were developed byYarrows and were widely used on ships, particularly warships....

.

Boiler

Although designed by Yarrow, boiler construction was actually carried out by John Brown
John Brown & Company
John Brown and Company of Clydebank was a pre-eminent Scottish marine engineering and shipbuilding firm, responsible for building many notable and world-famous ships, such as the , the , the , the , the , and the...

 in Sheffield.

The boiler resembled two elongated marine Yarrow boiler
Yarrow boiler
Yarrow boilers are an important class of high-pressure water-tube boilers. They were developed byYarrows and were widely used on ships, particularly warships....

s, 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
Locomotive frame
A locomotive frame is the structure that forms the backbone of the railway locomotive, giving it strength and supporting the superstructure elements such as a cab, boiler or bodywork. The vast majority of locomotives have had a frame structure of some kind...

, placing the water drums at the limits of the loading gauge
Loading gauge
A loading gauge defines the maximum height and width for railway vehicles and their loads to ensure safe passage through bridges, tunnels and other structures...

. The forward "boiler" region was narrow-set, with its water drums placed between the frames. The space outboard of the tubes formed a pair of exhaust flues leading forwards. A large space outside these flue walls but inside the boiler casing was used as an air duct from the air inlet, a crude rectangular slot beneath the smokebox door, which had the effect of both pre-heating the combustion air and also cooling the outer casing to prevent overheating. Longitudinal superheater
Superheater
A superheater is a device used to convert saturated steam or wet steam into dry steam used for power generation or processes. There are three types of superheaters namely: radiant, convection, and separately fired...

 tubes were placed between the steam generating tubes. 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 of 450 psi (31 bar; 3,103 kPa) as opposed to the 180 psi (12 bar; 1,241 kPa) of the contemporary Gresley A1 locomotive
LNER Class A1/A3
The London and North Eastern Railway LNER Gresley Classes A1 and A3 locomotives represented two distinct stages in the history of the British 4-6-2 "Pacific" steam locomotives designed by Nigel Gresley...

s.

Motion

This remarkable apparatus was based on a Gresley pacific
LNER Class A1/A3
The London and North Eastern Railway LNER Gresley Classes A1 and A3 locomotives represented two distinct stages in the history of the British 4-6-2 "Pacific" steam locomotives designed by Nigel Gresley...

 4-6-2 chassis, although with an additional axle to accommodate the extra length. This resulted in a 4-6-4
4-6-4
Under the Whyte notation for the classification of steam locomotives, 4-6-4 represents the wheel arrangement of four leading wheels on two axles , six powered and coupled driving wheels on three axles, and four trailing wheels on two axles .Other equivalent classifications are:UIC classification:...

 wheel arrangement, making No. 10000 the only standard gauge 4-6-4 tender engine to run on a British railway.

In UIC
UIC classification of locomotive axle arrangements
The UIC classification of locomotive axle arrangements describes the wheel arrangement of locomotives, multiple units and trams. It is set out in the International Union of Railways "Leaflet 650 - Standard designation of axle arrangement on locomotives and multiple-unit sets". It is used in much...

 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
Bogie
A bogie is a wheeled wagon or trolley. In mechanics terms, a bogie is a chassis or framework carrying wheels, attached to a vehicle. It can be fixed in place, as on a cargo truck, mounted on a swivel, as on a railway carriage/car or locomotive, or sprung as in the suspension of a caterpillar...

 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 high pressure necessitated compound
Compound locomotive
A compound engine unit is a type of steam engine where steam is expanded in two or more stages.A typical arrangement for a compound engine is that the steam is first expanded in a high-pressure cylinder, then having given up heat and losing pressure, it exhausts directly into one or more larger...

 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
August von Borries
August Friedrich Wilhelm von Borries was one of Germany's most influential railway engineers, who was primarily concerned with developments in steam locomotives....

 principle and using an inside half-length expansion link.

In service

The locomotive was completed at Darlington Works
Darlington Works
Darlington railway works, known in the town as North Road Shops, was built in 1863 by the Stockton and Darlington Railway in the town of Darlington in the north east of England.-NER History:The first new locomotive was built at the works in 1864...

 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.

Rebuilding

When it was deemed that no further progress could be made, the locomotive was taken to Doncaster Works
Doncaster Works
Doncaster railway works is in the town of Doncaster, South Yorkshire, England.Always referred to as "the Plant", it was established by the Great Northern Railway in 1853, replacing the previous works in Boston and Peterborough...

 in 1936 and rebuilt with a conventional boiler and three simple expansion cylinders on the normal Gresley layout
Gresley conjugated valve gear
The Gresley conjugated valve gear is a valve gear for steam locomotives designed by Sir Nigel Gresley, chief mechanical engineer of the LNER, assisted by Harold Holcroft...

. A modified A4
LNER Class A4
The Class A4 is a class of streamlined 4-6-2 steam locomotive, designed by Nigel Gresley for the London and North Eastern Railway in 1935. Their streamlined design gave them high-speed capability as well as making them instantly recognizable, and one of the class, 4468 Mallard, still claims the...

 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, 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, and also the "Galloping Sausage" as a result of its bulging 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.

On 1 September 1955, 60700 had just departed from Peterborough
Peterborough railway station
Peterborough railway station serves the city of Peterborough, England. It is located approximately north of London Kings Cross on the East Coast Main Line...

 when the front bogie
Bogie
A bogie is a wheeled wagon or trolley. In mechanics terms, a bogie is a chassis or framework carrying wheels, attached to a vehicle. It can be fixed in place, as on a cargo truck, mounted on a swivel, as on a railway carriage/car or locomotive, or sprung as in the suspension of a caterpillar...

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 bogie.

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

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