THE ALBANIAN people have a story that the Creator recently visited the earth and was astonished to find how it had changed. “Why, this is not the earth I created,” He said. “Everything has changed. My forests are cut down; My rivers have been diverted from their courses; My hills have been blasted away, and My mountains have been robbed of their minerals. The whole face of the earth has been altered.” But in the course of His roamings, the Creator suddenly came upon the land of Albania. “Ah!” He exclaimed in delight. “Here is a bit of earth untouched by man. It is still just as I made it.”
Man’s ambition to make over the face of the earth to his own liking dates far back of the present age of machinery. However, the work of the ancient engineer was accomplished only at the expense of decades and generations of hard manual labor. To-day, with powerful and gigantic machinery to do our bidding, we do not hesitate to change the course of rivers, to level off the hills, to carve highways through the mountains and pierce them with tunnels, to bore into their depths for treasure and drive deep holes into the bowels of the earth in quest of liquid fuel. We are able to machine the earth in much the same way as a piece of metal is machined in the machine shop. In fact, the drill, the circular saw, the slotter, and even the milling machine have their counterpart in the excavating machinery of to-day. Of course we cannot expect to find the counterpart of such machines as the lathe, boring mill, and planer, in which the work revolves against the tool, because this planet of ours is rather too big a piece of stock to be placed between lathe centers or to be bolted to a planer bed.
MECHANICAL MONSTERS
The twentieth century finds this planet again stocked with monsters larger and more powerful than the gigantic saurians that dominated the earth in the Jurassic and Cretaceous epochs, but our mighty fire-breathing, steel-sinewed beasts are humbly subservient to the will of man.
The spectacle of a large steam shovel at work makes one feel at once very small and very big. Before the work of this monster the human shoveler shrinks to the proportions of a mere insect. Seven to eight cubic yards shoveled into a cart is considered a fair day’s work for a laborer, but a big steam shovel can easily gobble up as much material in two bites. However, when we contemplate that this mammoth machine is a human creation and an absolute slave to human command, we are rather inclined to be puffed up with the greatness of man.
Steam shovels are ideal machines for excavating railroad cuts and were primarily developed for just such work. The general operation of the machine is very similar to that of hand shoveling. The shovel proper consists of a big scoop or dipper and a dipper handle which correspond respectively to the blade and handle of a hand shovel. Like the shovel, the dipper is supported at two points. The dipper is suspended by a chain from the end of a boom while the handle of the dipper is also supported in the boom. By loosening the hoisting chain the dipper is lowered to the ground, and by moving the handle forward the toothed cutting edge is made to bite into the ground or sand bank. The hoisting chain then hauls up the dipper, making it scoop out the bank, after which it is swung to one side over a car on an adjoining track. The rear of the bucket is fitted with a door which is opened by a spring latch and the contents are emptied out. Some of the largest steam shovels for ordinary grading have dippers with a capacity of 5 cubic yards. They are not confined to railroad grading, but are applicable to any excavation where a firm footing is provided for the heavy machine. They are even used for excavating the cellars of large city buildings. The machine must be supported on road wheels or on skids. When used for excavating sewer trenches, it is sometimes mounted on a platform spanning the trench. However, the steam shovel is rather limited in its reach. The largest ordinary steam shovels have a clear lift of but sixteen feet and can make a cut only sixty feet wide at the top.
For more extensive excavating as well as for digging ditches and trenches the drag-line excavator has recently come in to use. In these machines a scraper takes the place of the dipper. This is suspended from the end of a long crane and it is dragged along the ground by a cable, scooping up a load of earth. In some cases the scoop or scraper is merely attached to a cable leading from the hoisting engine to an anchorage and back to the engine. To adapt excavating machines for service in soft ground they are mounted on broad wheels or on track-laying tractor surfaces. One peculiar form of walking traction used by a drag-line excavator was described in Chapter XIII.
DITCHING AND TRENCHING MACHINES
For digging narrow ditches and trenches, particularly for sewers, water mains, gas-pipe lines, etc., a number of very interesting machines have been invented which are of two general types, the endless chain and the wheel excavators. The first type consists of a traction engine with a ladder at the rear that drops down into the trench. About this ladder runs an endless chain which carries a series of scoops or buckets. These are dragged up against the breast of the work and carry the excavated earth to the top of the ladder where it is dumped upon a transverse belt conveyor and carried to one side of the trench. With the larger sizes of chain excavators, trenches may be dug to a depth of twenty feet and the width of the trench may be from two to six feet wide.
The wheel type of trenching machine is similar in principle to the chain excavator. Instead of the chain of buckets, it has a wheel fitted with buckets. In one prominent type the wheel has no hub or spokes, but consists of a rim that is supported on and is turned by four friction rollers mounted in a rigid frame. This frame is mounted on a boom which can be raised or lowered as desired. Such machines can commonly dig to a depth of a dozen feet or so.