BEGINNING TO BUILD A “PACIFIC” EXPRESS LOCOMOTIVE AT DONCASTER WORKS. The main frames in position.
FIRST of all, in building a locomotive the constructors start just as they would in building a house -
The two ends of the boiler that produces the steam are mounted on this framework; the cylinders that turn the steam into work are bolted to the main frames, and with them all the complicated machinery by which the steam enters and leaves the cylinders; and then the whole of the engine, boiler, cylinders and frames, is dropped on to the wheels. In the photograph above you can clearly see the long frames of the engine, with the necessary spaces cut in them to fit over the axles.
BUILDING A “PACIFIC” ENGINE: outside cylinder and piston-
Sometimes the cylinders of the engine are arranged outside, where you can see them; sometimes they are inside, between the frames, where they are hidden under the boiler; and when an engine has more than two cylinders, you will find them both inside and outside. The trouble about inside cylinders is that you can only make them up to a certain size, because of the main frames on either side. And although you have a little more room available when the cylinders are outside, even then you are limited to a maximum of 22 inches in diameter. Bigger cylinders than that would hit the platforms and other structures that are often so close up to the line.
This is one of the problems that always cramp the British locomotive engineer so seriously in his designs. Although our wonderful railway pioneers of the early days gave the idea of the railway to the world, yet they did not see far enough ahead. The other countries that copied the idea, and especially America, profited by our experience over here, and left more room round their tracks.
The Americans, although their “gauge” (the distance between the lines) is the same as ours, have at least three feet more room vertically in which to build than we have, and proportionately in width too. So the biggest American locomotives are twice, and more than twice in some cases, the weight and power of the biggest that we can build in this country.
BUILDING AN ENGINE AT SWINDON WORKS: main frames, showing cylinders and saddle for smoke-
Bigger boilers mean more steam, and bigger cylinders mean a better opportunity of using it up; bigger boilers and bigger cylinders are therefore necessary if you want more power. So when the British locomotive designer wanted to get more tractive power than he could with a pair of 22-
On other railways four cylinders are more popular; one of the best-
Quite another arrangement of cylinders is that known as “compound”. The most extensive series of compound engines in the country is found on the Midland Division of the LMS, which will soon have nearly two hundred of them. In these engines the steam is led from the boiler into one large cylinder, known as the “high pressure” cylinder, between the two main frames; and when it has done its work in that, it is led on into the two “low pressure” cylinders, which are outside the frames, in order to do some more. Compound engines are used very extensively on the Continent of Europe, but they are not so popular over here.
All locomotive engines throw a lot of unused power out of their chimneys; the force with which the “puffs” are ejected does not leave that in much doubt. Steam enters the cylinder at one end, pushes the “piston” forward and so turns the driving wheels round; then that very important mechanism known as the valve-
But what becomes of the steam already in the cylinder? The same valve-
In many modern engines the valve-
A NEAR VIEW OF THE VALVE-
You will notice in this photograph the end of the “piston-
You will well understand that the flying round of these heavy parts, when the engine is in motion, and especially at very high speeds, would be likely to lead to very unsteady riding unless something were done to counteract these disturbing forces. So the engine is “balanced” in various ways, the most familiar of which is the balance-
I well remember once seeing a big pair of driving-
Another matter in connection with both wheels and motion to which very careful attention must be paid is that of lubric-
And then the “axle-
BUILDING A “ PACIFIC ” ENGINE AT DONCASTER: the boiler in position on the frames.
And now a word or two about steam. You can see more clearly the details of boiler construction in the “undress” loco-
ENGINES IN THEIR “WHITE JACKETS” AT SWINDON. The two engines on the left have been fitted with their asbestos “clothing” round the boiler-
Now, if you look at the big Great Western boiler, you will see that it is in two parts. At the back is the “fire-
Inside the fire-
STANDARD GREAT WESTERN LOCOMOTIVE BOILER. Showing fire-
You must remember, first of all, that the locomotive boiler has to produce steam at a faster rate than any other kind of boiler there is. To produce steam fast means to burn coal fast, and to burn coal fast means plenty of draught. The draught for your kitchen fire at home is obtained by having a chimney as high as the house; but this is clearly impossible on the locomotive, where we have only a total of just over 13 feet in height in which to build. This is where comes in the value of the escaping steam from the cylinders, to which I referred previously. It is a principle which was discovered long ago by the famous engineer, George Stephenson, and which was embodied in his engine, the “Rocket”, as early as 1829.
The steam, as it escapes from the cylinders, is carried into a vertical pipe in the smoke-
THE INNER FIRE-
This strong draught enables the coal to burn rapidly and fiercely ; and the heat so produced is then drawn through all those myriads of boiler-
Now the barrel itself, as well as the space between the inner and outer fire-
The fiercer the blast of the escaping steam is, so much the stronger the draught, and so much the more rapidly can steam be produced if required. So the locomotive is able to adapt itself readily to very hard work, when necessary, or to steam more easily, when the load is lighter or the speed desired is not so high.
You will also see, on the front of that Great Western boiler, a curious collection of pipes, which seem to run in all dirctions from the box, or chamber, that is fixed across the upper part of the barrel. This chamber, which is called a “header”, forms with the pipes part of the “superheater”, with which every modern engine is equipped.
The boiler is never kept quite full of water up to the top, as space must be left in which the steam may “collect”. On the top of most locomotive boilers you will see an arrangement near the centre, rather like a bowler hat in shape, and known as the “dome”. This covers a chamber opening out of the boiler, in which works the regulator -
FIREBOX OF “PACIFIC” ENGINE, CAB SIDE.
Notice myriads of stay-
When the driver opens his regulator, the steam rushes along the main steam-
Into these flues are led the array of little steam-
The third of the fittings generally seen on top of a locomotive fulfils a very important duty. On the Great Western boiler it takes the place in the middle of the barrel usually occupied by the steam-
I need not remind you how important this is; when the engine is standing, or when steam is shut off during running, the increasing pressure of steam in the boiler has no means of escape other than these safety-
Amongst the other external details of the engine, you will notice the coverings to the upper part of the driving wheels, usually known as “splashers”. In American engines splashers are unknown, because the “running-
THE MAIN ERECTING SHOP, SWINDON WORKS. One of the overhead cranes is lifting a 90-