STEPHENSON’S “Rocket” of 1829 gave us substantially the steam locomotive as we have it to-
One reason for the appearance of so many unconventional locomotives in the early days was the disbelief entertained by so many engineers in the tractive power of the smooth wheel on the smooth rail. Hence such contrivances as locomotives designed to be worked by a species of propellers that were forced out backwards against the ground and then raised again, after the fashion of a horse’s legs. This device was patented both for locomotives and for “steam carriages”. Moreover, the pioneer builders seem to have had a curious aversion from the use of horizontal cylinders, as is to be seen in such typical examples as the “Rocket” and the “Invicta”. The latter was built by Robert Stephenson & Company for the Canterbury and Whitstable Railway in 1830, and was designed on much the same lines as the “Rocket”, save that its four wheels were coupled. This was, by the way, one of the earliest instances of coupling. Before the “Invicta” appeared the cylinders were often placed upright on the top of the boiler, whence motion was imparted to the driving wheels by a complicated structure of cranks and levers, the idea being derived, in principle, from Watt’s beam engine. An example of this design is Stephenson’s “Locomotion No. 1”, with which the Stockton and Darlington was opened in 1825. This also was a four-
While on the subject of these early engines we may recall the little-
Between the “Rocket” and the “North Star” we have to note the revival of a type of motion that had already been seen at an earlier day, namely the bell-
The “Earl of Airlie” is worthy of record, since in the following year the bell-
Unconventional features were characteristic of practically all the designs of one of the great early British locomotive engineers, Thomas Russell Crampton. He was an ardent believer in a theory that carried a good deal of weight in its day, that of the low centre of gravity. He designed a six-
A variant of the Crampton locomotive was a “patent express engine” in which the drive was on to an intermediate crank-
Another and still more unusual arrangement of intermediate crankshaft was found on a locomotive built in 1848 for the South Yorkshire Railway. This was of the 0-
The theory of the low centre of gravity found its extreme expression in the “Cornwall”, built in 1847 by Francis Trevithick, for the London and North Western. This locomotive had driving wheels of the exceptional diameter of 8 ft 6-
Large as were the driving wheels of the “Cornwall”, they did not establish a record. The 4-
Details of the performance of these remarkable locomotives are scanty, but it is certain that the locomotives were not a success. The mounting of the motion on a carriage separate from the boiler (again the result of the low centre of gravity theory) resulted in insufficient adhesion, while the heating surface (623 sq ft) was not nearly enough for the 16-
Among unconventional locomotives worthy of mention are the earlier Webb compounds. The special feature of these locomotives, which for many years hauled the fastest and heaviest passenger express trains on the London and North Western Railway, was that their designer dispensed with the use of coupling rods.
In 1882 appeared the “Experiment”. This had two independent pairs of driving wheels of equal size, and a small pair of leading wheels, the arrangement being known as 2-
In their day the Webb uncoupled compounds were the centre of a storm of criticism and controversy. One argument used against these engines was that the absence of coupling rods contributed to imperfect synchronization of the two pairs of driving wheels. Their coal consumption was also a subject of criticism, but it should be remembered that these compound locomotives hauled, without assistance, trains that bad previously been double-
THE TURBINE of the engine develops 2,000 hp at a shaft speed of 10,500 revolutions per minute. The high speed turbine shaft is geared to the driving wheels, and reversing is effected by introducing an idler pinion into the gear train. This locomotive made several trial runs in 1926 on the LMS Railway.
The next locomotive peculiarity calling for comment is the steam tender. To some extent Harrison may be said in the “Hurricane” and “Thunderer” to have anticipated the idea; but it found concrete expression in the locomotive introduced by Archibald Sturrock on the Great Northern Railway in 1863. The steam tender was not the invention of Sturrock, since a locomotive thus equipped was built for the Lyons and St. Etienne Railway by the French engineer Verpilleux as far back as 1843. In Great Britain, however, the design is particularly identified with the Great Northern Railway.
The salient feature of the Sturrock locomotives was that the tender constituted a separate engine, although fed from the boiler of the locomotive proper. The locomotives had six-
Early Articulated Locomotives
Another unconventional type is the articulated locomotive. Its origin is due to the search for an engine capable of negotiating sharp curves and yet powerful enough to pull an adequate load up severe gradients. The solution was found in the flexible locomotive. This is, in effect, two engines coupled together. In 1852 the Austrian Government offered a prize for the best design for a locomotive to work the heavy gradients of the Semmering incline. None of the designs submitted meeting with approval, an articulated locomotive was built for this line by the Belgian firm of John Cockerill. This had a double-
The next important development was the Mallet articulated locomotive. This had a single boiler, but two sets of wheels and driving gear. Thus it was really two engines in one. Mallet’s locomotives were compound, the high-
The Garratt locomotive, which is largely used in South Africa, among other countries, is a further development of the idea of articulation. This also comprises virtually two engines in one. In this design, however, the boiler has no wheels immediately below it, an arrangement that permits of a larger boiler diameter than would otherwise be possible; and the wheels, cylinders, and valve gear are placed beneath the tank at either end. A typical example is the 2-
HIGH PRESSURE streamlined locomotive No. 10000 on the turn-
In the Shay geared locomotive the problem of steep gradients and sharp curves is tackled in a different manner. In 1873 Ephraim Shay, operating an extensive sawmill in the Michigan lumber country, thought of a geared locomotive, in which the power developed by the engine might be transmitted through shafting to the wheels. An experimental locomotive proving successful, the idea was rapidly developed. To-
From the earliest days locomotive engineers have exercised their ingenuity in devising means of increasing adhesion, partly, although by no means entirely, in connexion with the problems of mountain railways. In fact, the rack-
In the eighteen-
The first Fell locomotives were built for the Mont Cenis Railway, after a test with an experimental engine on the acutely graded High Peak Railway, in Derbyshire. Locomotives of this type have also been used in Brazil.
Apart from the fairly common rack locomotive, a number of railways have made use of the combined rack and adhesion type, India and Chile being among the countries where they are to be found. A unique type, of which the first example was built in England in 1887 for the Puerto Cabello and Valencia Railway, South America, uses the rail wheels only as carrier, the motion being imparted by the Abt cog-
The Transandine engines are unusual. In early examples the front unit was arranged for combined rack and adhesion work-
The auxiliary engine has also been used, in the form of the booster, both in England and the United States, as a source of reserve power on ordinary adhesion locomotives. The former Great Northern Railway fitted a booster to one of its “Atlantic” locomotives. A noteworthy modern example in British practice is the London and North Eastern “Mikado” (2-
These locomotives, which were the first in England to have the 2-
Many locomotive types merit the epithet unconventional not on account of any peculiarity in their mechanism, but as the result of unusual external design. In this category must be included a feature at one time not uncommon in the United States, in the shape of a cab perched centrally on the top of the boiler, an arrangement adopted in order to give the driver a better look-
The “Decapod” tank engine was also of an unconventional design. It was built for the Great Eastern Railway in 1902 to show that the acceleration associated with electrical working could be obtained with steam. The “Decapod” was able to attain thirty miles an hour in thirty seconds from the dead start with a 300-
Our survey would be incomplete without a reference to the numerous types of locomotive designed for specialized conditions of service. Prominent among these are “fireless” locomotives, built for use on factory and dock railways, on lines serving mines and explosive works, and elsewhere when it is desired to minimize the risk of fire and explosion. The fireless locomotive is a steam engine requiring no fuel. It is charged with high pressure steam sufficient for several hours’ working, and the steam leaves the boiler and actuates the cylinders in the usual manner. These locomotives can be distinguished by the absence of a chimney.
TRIPLE EXPANSION. This most unusual 4-
Another specialized type is the crane locomotive, used for works purposes. This combines a locomotive with a crane, which forms an essential part of the design. A typical example, as used on the Great Western Railway, is an 0-
It has already been mentioned that the line between the unusual or unconventional locomotive and the freak engine may be difficult to draw. Moreover the freak locomotive of to-
The locomotive practice of the Great Western Railway was characterized by two features of special interest during the last years of the broad gauge -
5 ft 6-
Only two tandem compounds, originally constructed as 2-
No. 7 was built for the standard gauge, while No. 8 was a convertible locomotive. The former had high-
Equally unsuccessful was the four-
Of the two locomotives now to be described, only one of each pattern was built. These were the “James Toleman” and the Kitson-
A Geared Locomotive
Very little has been recorded of its performance, and the story that it insisted on running backwards during its Chicago trials is no doubt malicious; but it was certainly not a success, and, all things considered, may be regarded as coming within the category of genuine freaks.
Since a description of the Kitson-
By way of conclusion, a most unusual locomotive may be mentioned. In 1872 there was opened a little line known as the Oxford and Aylesbury Tramroad, although it never reached within miles of either Oxford or Aylesbury. It was worked at first by horses, which were afterwards replaced by one of the most extraordinary locomotives ever seen in any country. The machine was a four-
DRIVING EVERY AXLE, the Shay Geared Locomotive has twelve 4 ft wheels driven through gearing by three vertical cylinders, 17-
“Giant American Locomotives” on this website.