Engines That Have Made Railway History
THE FIRST LJUNSTRÖM TURBINE LOCOMOTIVE, invented by a Swedish engineer, it was built in 1921, and achieved some success on the Swedish lines. A similar engine was built in 1924 in Britain, and this locomotive covered 5,402 miles during some months service on the LMS. Transmission from the turbine to driving axles was by triple gearing. At 75 miles and hour, the turbine made 10,500 revolutions a minute, and the maximum tractive effort was 40,320 lb. The locomotive is seen here at St Pancras Station.
FROM time to time efforts have been made by locomotive designers, both in Great Britain and in other countries, to break away from traditional locomotive design in search of greater efficiency -
It cannot be disputed that, on the basis of thermal efficiency, the steam locomotive, in its ordinary form, is an inefficient heat engine. Taken over the whole course of its daily service, the overall thermal efficiency of the average steam loco-
But this bald statement needs a great deal of qualification and explanation. In the first place, the steam locomotive suffers by reason of the confined space through which it has to pass. This self-
This matter of draught goes to the root of locomotive design. As it is impossible to erect a factory chimney on a locomotive boiler, some description of forced draught is essential, if there is to be proper combustion of the fuel on the firegrate. As far back as George Stephenson’s “Rocket” of 1829, we find the escaping steam from the cylinders, after it had done its work, led up into the chimney so that the suction thus created might provide a draught for the fire. And to this day the same
Through the narrowed top of the blast-
heating surface thus takes a share in raising steam. In this connexion, also, it must be remembered -
But even to the most casual observer it must be obvious, as the loudness of the engine “exhaust” is heard escaping from the chimney, especially on starting, and when travelling at low speeds uphill, that a great deal of power is thus being thrown to waste. The shortness of the boiler barrel also makes it inevitable that a considerable amount of heat from the fire is wastefully lost out of the chimney. Here, therefore, are direct and substantial losses of efficiency directly due to the principle
It is for this reason that so much attention has been paid in recent years to valve-
of steam used in the cylinders during each stroke may have a greater initial capacity for expansion.
The result of this development in valve-
high speeds of the modern express locomotive. But even to these developments in efficiency there must be a limit. For the terminal pressure might get so low that ultimately it would fail to provide sufficient draught for the fire, and the boiler would refuse to steam.
There are many other factors which help to explain the low overall thermal efficiency of the steam locomotive. Though modern developments may succeed in raising the figure from seven to eight, nine, or possibly even ten per cent -
Even if the working of the locomotive were absolutely perfect -
“KING HENRY VII”, one of the Great Western Railway’s famous “King” class locomotives, which has been partially streamlined in accordance with th latest developments in speed design. Similar streamlining has been applied to “Manorbier Castle” of the “Castle” class. After some experiencce of running, however, the cylinder casings have been removed from both engines.
It is not surprising that one of the first directions in which experimenters have turned to get over the difficulty of throwing steam to waste has been propulsion by turbines instead of by ordinary reciprocating motion. If turbine propulsion is combined with the use of a condenser, the exhaust steam with all its heat is trapped, instead of being thrown to waste. Not only so, but the partial vacuum resulting from condensation increases the efficiency of the turbine itself, so that there is a
But here again, and to an even greater extent than in the design of a steam locomotive of the ordinary type, space and weight are crucial difficulties, especially in installing a condenser of the necessary size and capacity on a locomotive chassis. Other difficulties are that special forced draught (usually a fan) must be installed for the fire, independent turbines must be provided for reverse working, and gearing and other complications are essential, all of which influence initial cost considerably.
The first British turbine experiment was made in 1910, by the North British Locomotive Company, and the engine was designed jointly by the late Sir Hugh Reid and Mr. W. M. Ramsay. But the further complication of electrical propulsion was introduced, the turbine driving dynamos which produced the current used for the movement of the locomotive by means of
electric motors. The two ends of the frame were supported by eight-
of the impulse type running at 3,000 revolutions per minute, coupled to a continuous-
Next came a second turbo-
which supplied current to four motors as before, with a total horse-
Later experiments dispensed with the electrical transmission. A handsome exhibit at the Wembley Exhibition of 1924 was the Reid-
chimney at the trailing end.
A WORKING PRESSURE OF 450 lb per square inch was planned in locomotive No. 10000 of the LNER by the use of a marine water-
Meanwhile some promising experiments had been made in Sweden by an engineer named Fredrik Ljungström, leading to the construction of a condensing turbo-
carrying the firebox end; then came the group of three driving axles, driven by gearing, and another pair of wheels at the rear end which was used for reverse working. At 9,200 revolutions a minute the main turbine developed 1,800 horse-
This apparent success led the well-
Transmission from the turbines to the driving axles was by means of triple reduction gearing. At 75 miles an hour, the turbine made 10,500 revolutions per minute, and the maximum tractive effort developed at the drawbar was 18 tons. Steam was generated at a pressure of 300 lb per sq in. The complete locomotive weighed 143¾ tons in running trim. It proved quite capable of working ordinary express services on the Midland with heavier loads than those taken by the
reduction in coal consumption, and without the advantage of higher thermal efficiency the additional cost of construction
could not be justified.
In 1935 an entirely new British turbine experiment was made, in which neither electrical transmission nor condensing equipment was used. This was Engine No. 6202 of the London, Midland and Scottish Railway, which was built to the joint designs of Mr. W. A. Stanier, the Chief Mechanical Engineer of the LMS, and of the Metropolitan-
LMS “TURBOMOTIVE”, a turbine-
The interest of this experiment centres not only in the trial of turbine propulsion without condensing, but also in the fact that it has been embodied in a locomotive which otherwise is of the standard LMS 4-
made, on a uniform basis, of the relative efficiency of drive with reciprocating motion, and of drive with geared turbines.
Steam is generated in the ordinary locomotive-
After use, the steam is exhausted in the ordinary way to the chimney, but a double blast-
lower than is customary with cylinder exhaust.
The turbine spindle, which is at right angles to the length of the engine, is coupled directly to the high-
clutch operated from the cab, with a safety device in the transmission to prevent the driver from attempting to reverse the locomotive except when it is motionless. Provision has also to be made for cooling the main turbine when the engine is running backwards.
A Successful Experiment
The boiler of the LMS “Turbomotive” has a total heating surface of 2,967 sq ft, to which the 32-
The weight imposed upon the driving wheels. or the “adhesion weight”, as it is known, creates a new record for a six-
coupled British locomotive, as it totals 70¾ tons, two of the axles carrying 24 tons each. But this is permissible in view of the entire absence with turbine propulsion of the “hammer-
No. 6202 is now in regular working, and has hauled some of the fastest trains on the LMS main line, including the Liverpool express booked from Crewe to Willesden Junction at an average speed of 64.5 miles per hour, on which time was gained. As this run includes severe service slacks at Stafford and Rugby, a less severe slowing through Norton Bridge (Staffordshire), and another over the mining subsidence at Polesworth (Warwickshire), some very fast running is required.
STEAM WAS GENERATED at the pressure of 300 lb per sq in in the 1926 turbine engine, tried out on the LMS. The locomotive successfully worked express services on the Midland Division of the railway. The engine weighed 143¾ tons in working order, and proved efficient in operation but though economies were effected they did not lead to the construction of other engines of this type.
Details have been received from the LMS Railway of two notable runs made by No. 6202 in working this train. On the first occasion, with a load of 331 tons tare (345 tons loaded), the 152.7 miles from Crewe to Willesden were run in 131 minutes, representing a gain of eleven minutes on schedule and an average speed of 69.8 mph. Two notable features were a minimum of 72 mph at the conclusion of the fifteen miles ascent from Bletchley to Tring, and a sustained maximum of 90 mph on the reverse slope of the Chilterns. On the second journey, with a load of 362 tons, the time from Crewe to Willesden was 138 minutes (overall average 66.2 mph), including an average of 75.6 mph over the 67.2 miles between Welton (Northants) and Wembley (Middlesex). The maximum speed on this second run, which was made under ordinary service conditions, was 86½ mph and the engine was not only running well within its capacity throughout, but was several times “eased” to avoid too early an arrival.
Up to the moment of writing no dynamometer car trials have yet been carried out with the “Turbomotive” such as would make available comparative data between its running costs and those of the standard LMS “Pacifies”. It is clear, however, that in performance alone -
But the real success or otherwise of this revolutionary machine will be judged by whether or not its turbine propulsion increases thermal efficiency by reducing coal consumption. It is hoped that the lower exhaust pressure of the steam may have this effect, and that the cost of maintaining the turbine equipment will not exceed that of maintaining an ordinary locomotive; otherwise the increased constructional cost of a design of this description will have no justification.
Another line of locomotive experiment has been that of considerably higher working pressures, to increase the range of expansion through which the steam can be carried. Briefly, the purpose is that of increasing efficiency by making the same weight of steam do more work. But the difficulty is that a boiler of the ordinary type cannot successfully be designed to raise steam at a pressure higher than 275 to 300 lb per sq in.
Novel types of boiler have thus been introduced to get over the difficulty. In Great Britain the best-
The process of steam-
The lower drums are connected with the upper drum by a large number of water-
chimney. Thus steam is raised by applying heat to the outside of water-
A GIANT SUPER-
To obtain adequate expansion, No. 10000 has been built as a compound locomotive, with two inside high-
pressure cylinders independently of that in the low-
No. 10000 has taken its turn with the ordinary LNER “Pacifics”, including the working in the summer of such trains as the non-
method has been adopted in the subsequent “Cock o' the North” and “Silver Jubilee” designs.
In the chapter entitled “Giant American Locomotives”, which begins on page 1184 of this work, a description is given of the experiments which have been carried out by the Delaware and Hudson Railroad with high-
STREAMLINING IN AMERICA. The “Hiawatha” is one of the fastest trains in the USA; the photograph shows one of the locomotives of unusual design which haul the train. The “Hiawatha” covers the 280.8 miles between Chicago and La Crosse (Wis.) In four hours and eleven minutes, giving an average speed of 67.1 miles an hour, including three stops, and the entire 410 miles to St Paul in 6½ hours.
The German Schmidt-
Steam for propulsion is raised in the main high-
An engine of this description, named “Fury”, was built by the LMS Company in 1929 on the same general lines as the
“Royal Scots”, but after test was withdrawn from service. Similar engines have worked on the German State Railways, the Swiss Federal Railways, the PLM Railway of France, and the Canadian Pacific Railway, and have given good results from the thermal efficiency point of view. The Canadian Pacific locomotive, No. 8000, a 2-
In particular, the Swiss example, using steam at 850 lb per sq in, showed an economy of 35 to 40 per cent in coal consumption, and of 47 to 55 per cent in water consumption, as compared with an ordinary locomotive of generally similar dimensions. But the fact that none of these types has been multiplied beyond the original experimental stage suggests that the cost of maintenance and the constant need for repairs have more than outweighed the saving obtained from the higher
overall thermal efficiency.
Since the rapid increase in train speeds which has followed the introduction of high speed Diesel-
differences in the maximum speeds which could be reached and maintained by Diesel and steam propulsion respectively would not have been so marked. But rapid progress is now being made in devising suitable streamlined coverings for locomotives designed to travel at high speeds continuously.
For probably it is only at speeds in excess of seventy or eighty miles an hour that streamlining begins to be really effective, so far as concerns a locomotive and train. Every projection from the surface of engine and coaches, and the space between engine and train, or coach and coach, are liable to cause eddy currents of air at speeds which cause the resistance of the air, opposing motion, to mount up. If that resistance can be reduced, then another source, this time external, of increased efficiency has been found. In France, as illustrated on page 1281 of the chapter “Through Southern France”, the Paris, Lyons and Mediterranean Railway provided its locomotives with “wind-
attempting to secure some diminution of head resistance. But present-
description than that embodied in these early experiments.
In Great Britain it has found its fullest expression in the new “Pacific” locomotives designed by the LNER for the “Silver Jubilee” high-
An experiment of a more limited description was made in 1935 by the Great Western Railway, which provided two locomotives -
of the outer air was thus shut off. In Germany two advanced designs of high-
“Giant American Locomotives”, already cited, the most remarkable examples of complete streamlining are the “Commodore Vanderbilt” streamlined “Hudson” 4-
The history of locomotive experimenting in modern times, therefore, seems in general to be that the advantages gained by radical alterations in the method of producing and utilizing the steam, though they may raise the overall thermal efficiency figure, tend to increase the costs of maintenance to such an extent as to force the locomotive engineers back to traditional
lines of design.
ON TRIAL. The Beyer Peacock Ljungström locomotive on the Midland main line near Mill Hill, Middlesex. The engine had a leading four-
You can read more on “A British Ljungstrom Turbine Locomotive” on this website.