What’s a Crampton Locomotive?
In 1835, the Great Western Railway had opened, enabling passengers to travel at the astounding speed of 60mph to board one of Brunel’s huge iron steamships for the fastest – ever Atlantic crossing to New York. To ensure a fast, comfortable run to Bristol, the railway was beautifully engineered to be as level and straight as possible, and the broad gauge of 7 feet and a quarter inch was adopted.
( picture of ‘Firefly’ class locomotive here )
This broad gauge enabled the boilers of the new locomotives to be larger ( important when construction from riveted wrought iron plates limited steam pressure ), with bigger fireboxes and larger heating areas. It also allowed a higher centre of gravity while maintaining stability. Larger driving wheels could be used, enabling piston speed to be lower, thus cutting down on wear and tear and allowing higher speeds to be reached before exhaust problems occurred. Lastly, larger cylinders could be placed between the frames under the smokebox, and there was also ample room for the Gooch valve gear.
Between 1839 and 1843, the young Thomas Crampton was responsible for producing many drawings for broad gauge projects, including all the drawings for the broad gauge ‘Firefly’ class of locomotive. As well as enabling the locomotives to be built, these drawings had an important political purpose: they served as proof to the Board of Trade and Parliament that the broad gauge allowed technical advances to be made which the much more commonly-used 4 foot 8 and a half inch gauge could not, and thus more investment in the broad gauge could be encouraged.
However, Crampton was convinced that far too much investment had already been made in the narrower gauge for the Great Western’s broad gauge to succeed in the long term. In his spare time, he worked quietly on a project of his own: a narrow – gauge locomotive that would not only equal a G.W.R. locomotive’s speed, power and stability but actually improve on them substantially.
He dealt with each problem systematically, thoroughly and with great originality. How can a large, powerful boiler be stabilised on a narrower chassis? By dropping it between the frames and lowering the centre of gravity. But won’t the large diameter prevent this? Not if the boiler is oval, rather than round! Won’t steam pressure make an oval boiler bulge outwards? Not if restraining rods are built into it, just like the metal rods with end plates built into houses to stop the walls bulging!
If the boiler is so low, where are the big driving wheels and their crank axle going to go? We can put the driving wheels at the back of the engine, right behind the firebox – which will mean that the firebox can be much wider with a huge heating surface. But where will the valve gear go? And how will the driver and fireman work with a big crank axle almost in their faces? There’ll be a set of valve gear on the outside of the locomotive on each side – much easier for maintenance. So there’ll be no need for a crank axle – the driving wheels will have a plain axle which we can put under the footplate.
Pretty radical stuff. But the new layout opened up fresh possibilities. If the cylinders were going to be outside the frames, why not put them above the running plate, right under the steam dome, enabling short pipes to deliver straight to the steam chests? Why not increase the heating area even more by having a trapezoid grate extending under the back of the boiler? How about radial axles for the two sets of wheels supporting the front end of the locomotive to enable curves to be taken at higher speeds? And, talking of higher speeds, wouldn’t it be wise to design in really generous bearing surfaces for all the wheels?
( picture of Tulk & Ley 1847 Crampton loco. )
Looking at Crampton’s design from a 21st. century perspective, it has to be said that the principals of a low centre of gravity, power from the rear, large driving wheels and an emphasis on wide, straight internal passages to deliver more, and consistent, power has a great deal in common with current Formula 1 practice!
( picture of Formula 1 racing car )
1843 was an important year for Crampton’s career. He left the G.W.R. to work for John and George Rennie’s engineering firm, and took out a patent for his revolutionary new locomotive design. Having parted company with Gooch, he felt himself free to publicize his new patent, and devoted his spare time to making continual improvements to it. A breakthrough came in 1845 when the British managers of the Namur and Liege Railway in Belgium ordered two locomotives with 7 foot driving wheels and a 14.5 sq. foot grate. They were built by the firm of Tulk & Ley in Whitehaven, a firm noted for innovative products which produced the first ‘tramp’ steamers for the coastal trade around Britain. One of these locomotives had its trial runs on the Grand Junction Railway, where it performed impressively. It was a stroke of good luck that the Grand Junction was about to merge with other lines to form the London & North Western Railway, a major rival of the Great Western, especially in the lucrative West Midlands area. The new LNWR, and particularly their Locomotive Superintendent McConnell, was eager to show investors that large driving wheels and high speeds were just as possible on the ‘standard’ gauge as on the G.W.R., and collaborated with Crampton to build three of his locomotives at their works in Crewe. The first two, ‘London’ and ‘Courier’ were very similar to the Tulk & Ley products, but with 8’ driving wheels. The third also had 8’ drivers, but was a real monster. It had the largest heating area yet, at 2,290 sq. ft., with a grate area of 21.5 sq. ft., the unusually high boiler pressure of 120 p.s.i. and impressive 18 x 24 ins. cylinders. Its exceptional length required three pairs of supporting wheels ahead of the driving pair. It was given the name ‘Liverpool’.
1851 was a triumphant year for Thomas Crampton. ‘Liverpool’ was displayed at the Great Exhibition, and won a Gold Medal. Another of his locomotives, ‘Folkestone’ of the South Eastern Railway , was also on show, as was one of the G.W.R. ‘Firefly’ class for which Crampton had provided the drawings. Gooch was not best pleased!
Finally, Crampton was able to announce the successful completion of his Dover – Calais submarine cable project at the closing of the Great Exhibition on 25th. September.
Unfortunately, despite their modern and progressive features, Crampton’s locomotives were not suited to Britain’s railways. Like the G.W.R. broad gauge locomotives, they really needed a straight, level railway built to a high standard to perform well. It has to be said that the majority of railways in Britain abounded in curves and gradients, and a great deal of trackwork was indifferent or poor.
Like all locomotives with large single driving wheels, the Cramptons found it hard to get up to speed quickly after a station stop. Also, they were poor pullers at low speed, and were at their best on short, lightweight expresses. Even in mid Victorian times, Britain’s population was increasing rapidly, and important towns which demanded regular services were often close together. Thus the real demand was for commuter and semi-fast inter-urban trains which required locomotives with smart acceleration from each station and strong pulling power for heavy loads rather than high top speeds. Even the prestige expresses could not always be guaranteed a clear run and were liable to be delayed by slower services up ahead.
Thus it was that the railways on which Crampton locomotives excelled were those built across the flat landscapes of Northern France and Northern Germany. It was the Cail brothers with their Paris engineering business which took up the Crampton patent in France and then embarked upon a painstaking reappraisal and refinement of every aspect of the design. It was a similar process to the work done many years later on the Citroen ‘police car’ to transform it into the beautiful, classic DS design.
( drawing of Cail ‘Crampton’ here )
The use of modern rolled steel for the boiler meant that a more slender, stronger round-sectioned design able to work at far higher pressure was used, and so the maximum advantage could be taken of the large Crampton grate and firebox. The large, rear-mounted driving wheel was produced with a much larger boss to increase adhesion weight. Care was taken to produce a beautifully-balanced valve gear and finely-machined bearings. Finally, all steam passages were made as smooth and straight as possible . . . . establishing a tradition for ‘internal streamlining’ which was later championed by great engineers such as de Glehn and Chapelon and became a key component of the best of French locomotive design.
The resulting 127 locomotives transformed French express train travel on the Est, Nord and PLM Railways. They easily outstripped their G.W.R. equivalents, frequently reaching 80mph, especially on the Paris – Strasbourg run. Their driving crews loved them. They dominated high speed rail travel for over 40 years, and some were still to be seen working at the turn of the century. Today, No.80, ‘Le Continent’, is still in working order at La Cite du Train in Mulhouse, and frequently pulls trains of visitors on their demonstration line.
( picture of preserved ‘Le Continent’ here ) Use Crampton-on-Strasbourg-Expr
In Germany, 135 Cramptons were built in the ten years between 1853 and 1863. Most worked on the Baden State Railway, and were built by Maschinenbau-Gesellschaft Karlsruhe. ‘Pfalz’ (Phoenix) lasted longest, remaining in service until 1903 and regularly running at 75mph. A replica, built in 1927, is now in the Deutches Bundesbahn Museum in Nuremburg.
( picture of ‘Pfalz’ here )
To summarize, Thomas Crampton’s locomotives didn’t really fit in with Britain’s already heavily used, urbanised railway system with its many curves, gradients and wide variations in track standards. However, on the relatively straight, flat, well-maintained permanent ways of northern Europe, they were masters of their light, high-speed expresses for nearly half a century, and heavily influenced the design of subsequent larger and more powerful locomotives. For these reasons, Thomas Crampton can justly be described as the Father of the standard-gauge high speed train.
( picture of French TGV here )