Andy Arthur - ThreadinburghThe thread about the “Galloping Sausage”; promising a lot but delivering a little
On this day (July 31st) in 1930, the curious LNER (London & North Eastern Railway) locomotive No. 10000 left Waverley station in Edinburgh at the head of the up Flying Scotsman. Hush Hush, as it was known, was an experimental prototype, fitted with a high-pressure water tube boiler: technology that ultimately proved more trouble than it was worth.
LNER locomotive no. 10000, leaving Waverley station at the head of the Flying Scotsman on the morning of July 31st 1930.This engine known as “Hush Hush” on account of the great secrecy that surrounded its design and construction; it was kept covered in sheeting whenever prying eyes were around to try and conceal what secrets lay beneath. Its internal company class name was the more mundane W1. The LNER and its designer hoped that its efficiency would make it the next great thing.From some angles it looked undeniably cool: sleek and furutistic.
No. 10000 from The Wonder Book of Engineering Wonders by Harry GoldingFrom other angles it looked like the mutant offspring of a wide-mouthed frog and a white pudding (it was painted light grey, initially). A great, wallowing, temperamental, steam-powered sausage.
No. 10000 at Darlington, June 1930The great technological secrete beneath its sausage-like exterior, and the reason for its curious appearance, was the custom-built water-tube boiler. These sorts of boilers were usually for high-end marine applications, so its construction was contracted out to the Yarrow & Co. shipyard in Glasgow. Without turning this story into a lecture about boiler design, in simple terms a traditional steam locomotive boiler is of the fire-tube type; hot combustion gasses go along tubes through a pressurised tank of water to hear it. By by its nature this structure has many built-in weaknesses where the tubes penetrate the boiler. In a water-tube boiler, it is the small tubes that contain the water, under pressure, heated by combustion gases from the outside. This allowed operated at 450psi vs. the usual 180-200psi of a typical railway fire-tube boiler of its time.
No. 10000’s boiler under construction at Yarrows, from “Gresley and Stanier” by F. J. BellwoodBecause it works at a higher pressure, the steam is hotter within a water-tube boiler, therefore its potential do do work is greater. In theory, compared to a lower-pressure boiler, it can produce more power from the same amount of fuel (or the same amount of power for less fuel) and therefore will be more efficient. The theory was all well and good, but at the business end the engineers did not understand how to exploit the high pressure steam in a “compound” system (that is, one where steam is used first at a high pressure to drive one set of pistons and then at lower pressure to drive another, to extract as much of the work from it as possible.)
10000 on the Forth Bridge, 1930No. 10000 was the brainchild of the LNER’s Chief Mechanical Engineer, Nigel Gresley; not usually a man associated with making engineering mistakes. Gresley, coincidentally and relevantly for this sites main themes, was an accidental son of Edinburgh: his family were from Derbyshire, but he entered this world early on a visit by his expectant mother to see a gynaecologist in the New Town.
Plaque dedicated to the memory of Nigel Gresley at Waverley Station, CC-by-2.0, Rod Smith via FlickrA cross-sectional illustration of “a Unique New Engine” with “a War-Ship Boiler” was printed in the Illustrated London News in January 1930. It shows just how tight a squeeze things were on the inside. One of the only design efficiencies that No. 10000 ended up having was a 14% smaller fire grate than a comparable locomotive.
Cross-section illustration of No. 10000, from Illustrated London News – Saturday 11 January 1930A water-tube boiler has no steam dome, so that familiar feature of a steam locomotive was missing. To accommodate the unusual size and profile of the water-tube boiler, the engine’s outer casing was carried all the way to the maximum permissible height, with the safety valves and whistles were recessed into the side. The odd-looking front end was designed to scoop air into the casing, to pre-heat it before entering the firebox, and to throw exhaust smoke clear of the cab
No. 10000 during construction at Darlington Works. From Illustrated London News – Saturday 11 January 1930With no visible chimney or dome and that big, silvery, pudding of an outer casing, No. 10000 looked odd enough. But as the boiler had to hang further back than usual it needed an extra pair of wheels for support, on a double-articulated rear truck, giving a highly unusual 4-6-2-2 configuration (4 leading wheels on a bogie, 6 driving wheels, 2 trailing wheels on a Cartazzi axle and then a futher 2 wheels trailing on a separate Bissel truck). No. 10000 was never officially named – name plates to christen it “British Enterprise” were optimistically cast – but these were never fitted, and it was probably a good thing on account of the technical headache and operational embarrassment that it turned out to be. As well as “Hush Hush”, the less than flattering nickname of “Galloping Sausage” was unofficially applied.
No. 10000, from “The steam locomotive : its form and function” by William Alfred TuplinNo. 10000 was tested on the mainline for quite few years, with various tweaks and changes being made to try and improve its performance. In some aspects it showed promise, but these were offset by its heavy coal consumption, high build and running costs, lower power and poor reliability. Its fundamental problem however, was that it was a totally unique design, when every other locomotive on the LNER had a fire-tube boiler; there was reduced commonality and no economy of scale. It was quietly rebuilt with a fire-tube boiler and new outer casing into an approximation of a standard A4 Pacific in 1937 (also designed by Nigel Gresley). In this guise it served the railway for longer than its original form, all the way into British Railways days as No. 60700.
No. 10000 on the right, with a line-up of standard A4 Pacifics. You had to look very closely for the extra pair of trailing wheels (not shown in this image) to tell it apart from the others. From “Foreword” by E. Royston Pike (1938) Our Generation, London: Waverley Book CompanyThe only major blot on the otherwise unremarkable and reliable service of its second life was an ignominious slow-speed derailment at Peterborough in September 1955 which saw No. 60700 end up sprawled on its side. There were no serious injuries, and the three men on the footplate were thrown clear and unhurt. The damage was not significant and the locomotive was righted, repaired, and put back in service for a further decade before being withdrawn for scrap. Its tender survived into preservation with the A4 Pacific No. 60009 “Union of South Africa“
The aftermath of the Peterborough derailment, Peterborough Advertiser – 2nd September 1955Note to readers: unfortunately in April 2026, a third-party plug-in more than exceeded its authority and broke many of the image links on this site. No images were lost but I will have to restore them page-by-page, which may take some time. In the meantime please bear with me while I go about rectifying this issue.
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