Chap. XXI. STEAM CONSIDERED AS A MOVING POWER.
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Application to Steam Boats . — The maritime engine is made more compact than thatusually employed in our manufactories, and, in order to diminish its height, the workingbeams are placed below the cylinder on each side: in engines of 200 horse-power, thecylinders are made 5 feet in height, and 53 inches in diameter, in order to save room ; theother portions of the engine do not materially differ from those we have already described.The shaft, upon which the paddle-wheels are fixed, is made to revolve by cranks placedupon it, in the same manner as the fly-wheel of a common engine: the paddle-wheels aremade like the common undershot, and bear on their rims flat paddle-boards : the marineengine may be either condensing or high-pressure, but the low-pressure condensing isgenerally used.
Loconwtives _The general description of the locomotives on the London and Southampton
line is as follows: —the engines have two horizontal cylinders, working to a double-crankedaxle in the driving-wheels : there are six wheels ; the diameter of the driving wheels is 5 feet6 inches, and the others 3 feet 6 inches, each of which have a nave of cast-iron, bound withtwo hoops of malleable iron ; the rims are also of the same metal, and well welded to therim, round which is a tire inch in thickness and 5 inches wide, the flange of which pro-jects 1 inch ; these wheels are all turned very accurately, and have a conical inclination :the cylinders are 13 inches in diameter, and have metallic spring pistons fitted into them,which make an 18-inch stroke.
The Boilers are cylindrical, 3 feet 3 inches in diameter and 8 feet long, and contain about120 tough rolled brass tubes, 1| inch in diameter at one end, and lj at the other, drawn ona mandrill; they are fastened to the boiler with steel hoops: the thickness of the tubesis No. 15. wire gauze, and the holes in the ends of the boiler are all parallel.
The Fire-box is of copper, -j*. of an inch in thickness, but where the tubes arefixed, the plate is ^ of an inch in thickness: the width of the fire-box internally is 3feet 6 inches ; length 2 feet 6 inches, and depth from the roof to the top of the fire-bars 3feet 4 inches; the water-spaces are 3 inches wide, and the roof and sides of the box arestayed with copper bolts, tapped and riveted.
The Axles. — The cranked axles are made of the best Eackbarrow iron, 5J inches in dia-meter at the crank pin, and it is turned down to 3$ inches for the outside bearings : the axlesfor the fore wheels are 3^ inches, and for the hind wheels 3} inches in diameter; they areturned throughout.
The Framing. _The engine is provided with four inside stay and bearing frames of
wrought-iron, with brass bearings to fit to the main axle on both sides of each crank, theaxle being properly turned to suit these bearings, and the frames are connected with thefire-box and cylinder beds, which form stays for their support. The outside frames aremade of well-seasoned ash plank, 3 inches thick and 7 inches deep, plated on both sideswith quarter-inch best Low’ Moor plates. These frames are 3 feet 2 inches clear above thesurface of the rails.
Feed Pumps _There arc two, made of brass fixed at the side of the boiler, the water-
spaces of which have an area of 2i inches clear.
The Chimney is covered w’ith a wire cap, and all its bearings and journals are case-hardened, and its height is 13 feet from the rails.
The Engine is worked by eccentrics, with single slide valves and steel facings, and thereare two safety-valves, w’ater-gauges, buffers, draw-bars, splash-boards, ash-pan, siphon cups,safety-bars in front, wood sheathing, brass ball and socket, communication pipes, steelsprings, and all other requisites to complete their working order.
The Tenders have their frames made with well-seasoned ash timber, with transverse anddiagonal braces well bolted together : the tank is of a horse-shoe form, and contains 700gallons of water; it is made of iron plates, ^ of an inch thick, and provided with cocksand pipes, to connect with the ball and socket feed-pipes of the engine : the wheels arc ofwrought-iron, 3 feet 6 inches in diameter, with wrought-iron tires inch thick.
The tenders are also provided with springs, break, buffers, long elliptical spring chainsto draw by, with a box of tools, oil-cans, shovel, and all other requisites to put it into aworking state.
Locomotive Engines differ from the ordinary steam-engine in their arrangement, and maybe said to consist of three several parts ; the square box which contains the fire, the boilerand its tubes, and the portion in front, where the cylinders and chimney are placed.
The usual construction is that with two horizontal cylinders, from 12 to 15 inches or morein diameter, fitted with single slide-valves and metal spring pistons, having a length ofstroke from 16 to 18 inches. The tire-box is open only at the bottom, and placed at theback part of the engine; it is made of copper, and has a door to admit the fuel ; the generaldimensions may be said to be 30 inches in length, from back to front 40 inches in width,and the height from the iron grate-bars at bottom to the top 39 or 40 inches: the fire-boxis entirely surrounded by water, except at the bottom, and where the opening is to admitthe putting on the fuel. The space for the water is about 3 inches in width, and where itis in contact with the cylindrical portion of the boiler it is a little more.
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