Passenger Locomotive
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228 JOURNAL OF THE INST. OF LOCO. ENGINEERS. THE MODERNBRITISH EXPRESS PASSENGERLOCOMOTIVE. Paper read before the Institution by F. W. BEESLEY (Graduate), Glasgow, on 19th January, 1922, at Glasgow. Paper No. 119." Between the locomotive built by George Stephenson and introduced for service on the Liverpool and Manchester Railway in 1829, and the present-day express passenger locomotive there is " a great gulf fixed." In appearance the locomotive built by Stephenson will not bear comparison, for example, with the massive and stately express main line locomotives recently constructed. " Picturesqueness " has not been sacrificed to design, for no one, however un- initiated, can see one of these triumphs of skill and thought without a feeling of admiration. From 1829 up to the present day the power of the passenger locomotive has gradually been increasing ; twc- cylinder engines giving place to four-cylinder compounds, and latterly the three-cylinder engine has come to the front in the form of compounds on the Midland Railway, " At- lantics " on the North-Eastern Railway, and more recently the new 4-6-0 type on the Caledonian Kailway. The first problems which face the designer of one of the present-day express locomotives are the fixed restrictions as to height, width and length, these being brought about by bridges, permanent way and sharp curves. The loco'motive is made up of three principal parts :- (I) The boiler and firebox, where the heat produced is used for the generation of steam ; (2) The cylinders and valves, where the energy in the steam is transformed into motive power ; and (3) The frame and wheels on which the boiler and cylinders are carried, and by which the tractive force at the r'ail is transmitted to the drawbar con- necting engine and train. * .4warded 2nd Prize for Graduate's Paper read before Scottish Centre. Silver Medal presented by Mr. David Smith, G. & S.W.R. Downloaded from jil.sagepub.com at CAMBRIDGE UNIV LIBRARY on June 4, 2016 THE MODERN BRITISH EXPRESS LOCO.-BEESLEY. ZZg Before taking each one of these parts and considering them in detail, it is advisahle to say a few words on the different types of main line locomotives which are at \present running on the various railways of this country. The word ‘‘ type ” means the several wheel arrange- ments adopted by the various railways. It does not, how- ever, follow that each railway company has the same tyw of locomotive for its standard main line work as the others. There are three types in use which may be said to be “ standard ” in this country. (Ij The four-coupled bogie passenger, or 4-4-0 loco- motive, which has a leading bogie and four coupled wheels. This type is by far the most popular of the three. (2) The ‘‘ Atlantic,” or 4-4-2 type, which has a leading bogie, four coupled wheels and a pair of trailing radial wheels. This type is used when a large firebox is desired. It may be mentioned that, with the exception of those of the Lancashire and Yorkshire Railway, all “ Atlantics ” are outside cylinder engines. (3) The ten-wheeler, or 4-6-0 type, which has a leading bogie and six coupled wheels. This type is used extensively on most of the railways, and is found in the form of a two-cylinder, a three-cylinder, or a four-cylinder’ engine. On account of its long coupled wheelbase, the result is a large and long boiler and a big firebox. It may be of interest to note that at present there are 3,457 engines of the 4-4-0 type, 1,083 of the 4-6-0 typer and 293 of the 4-4-2 type, forming 32 per cent. of the grand total of tender engines in this country. Other types, smaller than those already mentioned, are used frequently on some railways for passenger trains- such as the 2-4-0’s on the Midland and London & North- Western Railways, and the 0-4-2’s on the London, Brighton & South Coast and the London & South-Western Railways. Some of the leading railways are using extensively very large tank engines for their main line work, e.g., the London, Brighton 81 South Coast and Midland Railway 4-6-4 or “ Baltic ” type tanks, and the Caledonian, Great Central, London, Brighton & South Coast, and London & North-Western 4-6-2 or “ Pacific ” type tanks. To return to the subject of analysing the locomotive. The modern locomotive boiler has several good points. For its size and weight it is a quick steam producer. It can easily be ‘‘ forced ” when occasion demands, and, as is obvious, its shape is remarkably well adapted for its par- Downloaded from jil.sagepub.com at CAMBRIDGE UNIV LIBRARY on June 4, 2016 230 JOLJRNAL OF THE INST. OF LOCO. ENGINEERS. ticular purpose. Otherwise it is expensive, and although several attempts have been made to improve it, the bosiler universally used by all railway companies to-day remains essentially an enlarged pattern of the “ Rocket ” boiler. The boiler is made up of three main com,panents-the firebox, the barrel and smokebox-which will now be described. The inner firebox is a large rectangular chamber, the front end being the tubeplate, and the back end the door- plate. The roof of the firebox is formed by a large plate, which is called the “ firebox crown.” In this country all these plates are made of the best capper, although in America they are nearly always made of mild steel. There are two reasons for coppef being used:- (I) Copper is a much better conductor of heat than steel. (2) It is able to withstand the great strains brought about by repeated expansion and contraction far better than steel, which has a tendency to crack, especially in the corners. The flat surfaces of the sides and ends of the copper box are supported by stays made of best rolled soft copper bars screwed into both copper and steel shell plates and riveted over. These stays suffer very severely, especially when steam is being raised, from the fact that the copper plates became very much hotter than the steel plates, and, having also a higher coefficient of expansion than steel, the copper plate expands vertically relatively to the steel, gush- ing up the inner ends of the stays and causing them to become bent or broken. The flat firebox roof is supported either by gilder stays, with feet resting on the tubeplate and doorplate and connected throughout their length ta the roofplate by screws; or by direct stays made of steel rods screwed into both copper and steel plates and held with nuts inside the firebox, and riveted over on the outside of the shell [plate, or throat plate as it is sometimes called, and the back plate which forms the end of the boiler and has the firehole cut in it. This “ shell ” is riveted to the inner firebox through what is known as the foundation ring, which is a forged steel or wrought-iron frame bent round to form a large rectangle embracing the bottom of the firebox. The wrapper plate has a manhoie on top of it, which is used for a seating for the safety valves. A firegrate forms the bottom of the firebox: This consists of a series of bars arranged langitudinally, with spaces between them sa as to allow a passage for the air Downloaded from jil.sagepub.com at CAMBRIDGE UNIV LIBRARY on June 4, 2016 THE MODERN BRITISH EXPRESS LOCO.-BEESLEY. 23 I essential for the combustion of the fuel placed on top of the bars. The grate may be level or inclined at the back or front. It is the general practice here to place the firebox between the frames, and as the size of the grate is limited by the distance between the driving and trailing or the intermediate and trailing axles, as the case may be, it is obvious that unless some means were taken it would not be possible to burn enough fuel on such a small grate to produce the required amount of steam for the work'the engine has to do. This, however, is overcome by utilising the draught produced by the exhaust steam. Fixed to the bottom of the sides of the firebox by means of studs and nuts so as to be easily detached, is the ashipan, which is a box-like structure about a foot deep. It is provided with dampers, generally fixed at the front end on tender engines, but at the back as well on tank engines, which are required to run both ways. The ashpan is used to collect the ashes as they drop through the fire- bars, and also, when required, to prevent air entering through the firebars. By means of levers and catches in the cab, the driver is able to control the dampers. There is another component of the firebox which has not yet been mentioned, and without which the firebox would certainly not be complete. This is the firebrick arch, which is built up across the front part of the firebox, just below the bottom of the tubes, and rkaching over towards the firehole. It is inclined upwards, forming an arch across the box, thus its name. The arch deflects the fire over towards the back of the firebox, causing the heat to be more equally spread out over the whole of the inside of the firebox, and prevents cold air passing over and striking the ends of the tubes, thus reducing tube leakage.