Steam Engine Construction for the “Humboldt“
The engraving an the next page represents the interior of the engine-room of the Humboldt —a new steamer, which was lying at the dock at the time of our visit, receiving her machinery; though probably before these pages shall come under the eye of the reader, she will be steadily forcing her way over the foaming surges of the broad Atlantic. The machinery, as we saw it, was incomplete, and the parts in disorder—the various masses of which it was ultimately to be composed, resting an temporary Supports, in different stages, apparently of their slow journey to the plane and the connection in which they respectively belonged. The ingenious artist, however, who mode the drawings, succeeded in doing, by means of his imagination, at once, what it will require the workmen several weeks to perform, with all their complicated machinery of derricks, tackles, and cranes. He put every thing in its place, and has given us a view of the whole structure as it will appear when the ship is ready for sea.
There are two engines and four boilers; thus the machinery is all double, so that if any fatal accident or damage should accrue to any part, only one half of the moving forte on which the ship relies would be suspended. The heads of two of the boilers are to be seen on the left of the view. They are called the starboard and larboard boilers—those words meaning right and left. That is, the one on the right to a person standing before them in the engine room, and facing them, is the starboard, and the other the larboard boiler. It is the larboard boiler which is nearest the spectator in the engraving.
The boilers, the heads of which only are seen in the engraving, are enormous in magnitude and capacity, extending as they do for forward into the hold of the ship. In marine engines of the largest class they are sometimes thirty six feet long and over twelve feet in diameter. There is many a farmer's dwelling house among the mountains, which is deemed by its inmates spacious and comfortable, that has less capacity. In Lot, placed upon end, one of these boilers would form a tower with a very good sized room on each floor, and four stories high. The manner in which the boilers are made will be presently explained.
The steam generated in the boilers is conveyed to the engine, where it is to do its work, by what is called the steam pipe. The steam pipe of the larboard engine, that is, of the one nearest the spectator, is not represented in the engraving as it would have intercepted too much the view of the other parts. That belonging to the starboard engine, however, may he seen passing across from the Boiler to the engine, on the back side of the room. The destination of the steam is the cylinder.
The cylinder, marked C, is seen on the extreme right, in the view. It may be known, too, by its form, which corresponds with its name. The cylinder is the heart and soul of the engine, being the seat and centre of its power. The steam is generated in the boilers, but while it remains there it remains quiescent and inert. The action in which it mighty power is expended, and by means of which all subsequent effects are produced, is the lifting and bringing down of the enormous piston which plays within the cylinder. This piston is a massive metallic disc or plate, fitting the interior of the cylinder by its edges, and rising or falling by the expansive force of the steam, as it is admitted alternatively above and below it.
The round beam which is seen issuing from the centre of the head of the cylinder is called the piston rod. The piston itself is firmly secured to the lower end of this rod within the cylinder. Of course, when the piston is forced upward by the pressure of the steam admitted beneath it, the piston rod rises, too, with all the force of the expansion. This is, in the case of the largest marine engines, a force of about a hundred tons. That is to say, if in the place of the cross head—the beam marked H in the engraving which surmounts the piston—there were a mass of rock weighing a hundred tons, which would be, in the case of granite, a block four feet square and eighty feet high, the forte of the steam beneath the piston in the cylinder would be competent to lift it.
The piston rod, rising with this immense force carries up the cross head, and with the cross head the two side rods, one of which is seen in fall, in the engraving, and is marked S. There is a side rod on each side of the cylinders. The lower ends of these rods are firmly connected with the back ends of what are called the side levers. One of these side levers is seen in full view in the engraving. It is the massive fiat beam Marked L. near the fore-ground of the view. It turns upon an enormous pivot which passes through the centre of it, as seen in the drawing, in such a manner that when the cylinder end is drawn up by the lifting of the cross head, the other end is borne down to the same extent, and with the same prodigious force. There is another side beam, on the other side of the cylinder, which moves isochronously with the one in view. The forward end of this other beam may be seen, though the main Body of it is concealed from view. These two forward ends of the levers are connected by a heavy bar, called the Cross Tail, which passes across from one to the other. From the centre of this cross tail, a bar called the connecting rod rises to the crank, where the force exerted by the steam in the cylinders is finally expended in turning the great paddle wheels by means of the main shaft, S (I believe the author meant T), which is seen resting in the pillow block, P, above. These are the essential parts of the engine, and we now proceed to consider the mode of manufacturing these several parts, somewhat in detail.
source: Harper's Monthly Magazine May 1851