Crampton
The Crampton locomotive type was a distinctive family of express passenger engines characterised by their very large driving wheels placed behind the firebox and boiler rather than under them — an arrangement devised by Thomas Russell Crampton and patented in 1843 that allowed the use of enormous driving wheels (sometimes 7 ft or more in diameter) without raising the boiler to an impractical height. Crampton engines were built from 1846 onwards for several British and European railways, achieving considerable fame for high-speed running, and were especially successful in France and Germany where the Crampton type dominated express working on several major routes for decades.
Crampton's original insight was that the limitation on driving wheel diameter in contemporary locomotives was the height of the boiler: the larger the driving wheel, the higher the axle, and thus the higher the boiler and the higher the locomotive's centre of gravity. By placing the large driving axle behind the firebox rather than under the boiler, Crampton could use a very large wheel while keeping the boiler low, giving stable riding at high speed. The arrangement was unconventional — the driving axle was entirely behind the firebox, with only carrying wheels under the boiler itself — but it worked, and early Crampton engines achieved speeds remarkable for their era.
In Britain the Crampton type enjoyed a relatively brief vogue. The London and North Western Railway, the South Eastern Railway, and the Midland Railway all operated Cramptons in the late 1840s and early 1850s, but British locomotive engineers found that the adhesion of a single driving axle placed entirely at the rear of the locomotive was limited, and that the increasing weight of express trains demanded more adhesion than the Crampton layout could provide. British railways moved towards inside-cylinder 2-2-2 and 2-4-0 types with the driving wheels under the boiler. In France, however, the Crampton found a more enduring home: the Paris–Lyon–Méditerranée railway operated Cramptons extensively, and the phrase ‘prendre le Crampton’ — to take the Crampton train — entered French popular usage as a synonym for fast travel.
No original Crampton locomotive built for British service survives. The most accessible surviving Crampton is the French Le Continent of 1852, preserved at the Cité du Train museum in Mulhouse, France. The type's influence on subsequent British locomotive design was limited, but its European success demonstrated that unconventional solutions to the challenge of high-speed steam traction were commercially viable.
Design and development
Thomas Crampton (a former GWR draughtsman under Gooch) patented in 1842 an arrangement that addressed the conflict between large driving wheels and a low boiler centre of gravity: by mounting the driving axle entirely behind the firebox, the boiler could sit low between the leading bogie and the driving wheel, and the driving wheel itself could be made very large (typically 7 ft, sometimes 8 ft).
Cramptons were built in modest numbers for British railways — including the LNWR, the South Eastern, and the GNR — but the layout was much more enthusiastically adopted in France and Germany, where it became the standard express type for the 1850s and into the 1860s. Over 300 Cramptons were built for Continental railways.
Service and withdrawals
The British Cramptons were progressively withdrawn during the 1860s and 1870s as longer-wheelbase engines superseded them. On the Continent the type lasted longer; the last working Cramptons in Germany were withdrawn in the 1880s.
One Continental example, French Compagnie de l'Est No. 80 "Le Continent" (built 1852), is preserved at the Cité du Train in Mulhouse, France — the only surviving Crampton anywhere.
Identification features
Very distinctive: a single pair of very large (7–8 ft) driving wheels mounted entirely behind the firebox, a long low boiler running over the leading carrying wheels, and outside cylinders mid-way along the boiler driving the single rear axle. The layout is unmistakable.
Notable locomotives
- Le Continent (1852, Cité du Train, Mulhouse)