Engineers and their triumphs / the story of the locomotive, the steamship, bridge building, tunnel making

by F. M. Holmes

In the “Planet,” put upon the line shortly after the opening, the cylinders were placed horizontally and within the fire box. The engine drew eighty tons from Liverpool to Manchester against a strong wind in two and a-half hours, while on another occasion with a company of voters, it sped from Manchester to Liverpool, thirty-one miles, in an hour. But next year the “Samson,” which was still further improved, and the wheels of which were coupled so as to secure greater grip on the rails, hauled 150 tons at twenty miles an hour with a smaller consumption of fuel.

The locomotive had now become one of the wonders of the world. Since then its speed has been doubled. But all the improvements (with possibly one exception—that of the compound cylinder which is at present only partially in use) have been more in details than in principles. Thus the 70 or 80 ton express engine, which covers mile after mile at the rate of a mile a minute without a wheeze or a groan, is not very different essentially from George Stephenson’s locomotives, though its steam pressure is very much higher.

There are, for instance, the multitubular boiler, the furnace surrounded by water and communicating with the boiler, the horizontal cylinders acting directly on the driving wheels, and the steam-blast by which the waste steam is spouted up the chimney, creating a draught in the furnace.

These may be regarded as the more important of the essential principles, although there is diversity of details, more especially for the different work required. But the steam pressure is now much greater. Let us glance at a typical English locomotive. You might not think it, but the machine has about five thousand different parts, all put together as Robert Stephenson said “as carefully as a watch.”

At first sight you will probably not see the cylinders. The tendency in many engines now seems to be to place them inside the wheels, for it is urged that the placing of the heavier parts of the mechanism near to the centre lessens oscillation, and protects the machinery more effectually. Against this, it is said that the placing of the cylinders in that position increases the cost and the complication of the driving axle, and renders the pistons and valves more inaccessible for the purposes of repair. Both forms have their advocates, and the outside-cylinder form may be seen on the London and South-Western and some other railways, while the inside may be seen on the North-Western and others.

The boiler is of course the long, round body of the locomotive, and in English machines it is placed on a strong plate frame. Then as to the driving-wheels. Express engines, such as the splendid “eight-feet singles” of the Great Northern, have often, as the name implies, but one large driving-wheel on either side, and for great speeds this form is held to possess certain advantages. Certainly the performances of Mr. Patrick Stirling’s expresses would indicate that this is the case.

With steam raising the safety valve at a pressure of 140 lbs. to the square inch, the engines will whisk a score of carriages out of King’s Cross up the northern height of London at forty miles an hour, and then without a stop rush on to Grantham at near sixty. Standing on the platform at King’s Cross, with a large part of the immense driving-wheel hidden below you as it rests on the rail, you do not realise its tremendous size. Yet, let the engine-driver open the throttle, as it is called—that is, turn on the steam to the cylinders—and that huge wheel will revolve, and with its neighbour on the other side, haul after them that heavy train of carriages, and, gathering speed as they go, they will soon be rushing up the incline at forty miles an hour, and then on at sixty. It is a marvel of mechanism!

But then the compound engines that Mr. F. W. Webb, the engineer of the North-Western, builds for that Company can also perform remarkable things. The compound is the great modern improvement (some engineers might doubt whether improvement be the correct word) in the locomotive, effecting, it is said, an economy of from ten to fifteen per cent. in fuel. Now the compounding principle has been developed to such an extent in marine steam engines that it revolutionised steam navigation. But the application of the principle has not been so great in the case of the locomotive.

Briefly, the principle is this—the steam is sent out from the boiler at a high pressure, say 160 to 180 lbs. to the square inch, and is used in one or in a pair of high-pressure cylinders, and then used again, by means of its expanding power, in a larger, low-pressure cylinder. Mr. John Nicholson, of the Great Eastern Railway, suggested a compound locomotive before even the compound marine engine had been made, and his design was successful; but in 1881 Mr. Webb, of the North-Western, patented a compound locomotive, with two small high-pressure, and one large low-pressure cylinders, the latter twenty-six inches in diameter. Placed between the front wheels, the bright boss of this cylinder may be seen in shining steel as it flies over the rails.

The argument is that the compound burns less fuel and is more powerful than a non-compound of the same weight; but against this is launched the objection that the compound is more expensive to build, to repair, and to maintain. Still further it is argued, that a fast-speeding locomotive has not the time in its hurrying life to expand its steam in the tick of time between each stroke of the piston.