Engineers and Mechanics Encyclopedia 1839: Railways: Rawe and Boase
On the 19th of July, 1830, a patent was issued to Messrs. Rawe and Boase, of Albany-street, London, for "improvements in steam carriages and in boilers; and a method of producing draft." The specification of their patent contains a description, with drawings, of a complete locomotive carriage for the common road.
The boiler is entirely composed of stout wrought-iron tubes, leaving an internal diameter of an inch and three-quarters. The length or number of the tubes are, of course, arbitrary, depending upon the capacity of the boiler; in the instance before us, the boiler consists of 12 tubes; each individual tube is bent into a spiral figure of three turns, which are of equal diameter or breadth.
The first spiral tube thus formed, would contain within its coils a cylinder of 1 foot in diameter; the second spiral tube is curved in a parallel line to the first, but of about four inches greater diameter, so that it will lie outside of the first, and exactly circumscribe it, leaving between the two a space of about an eighth of an inch. Each successive tube of the whole twelve is curved in like manner, the coils of the whole being equidistant, but the diameter of each separate spiral is in succession 4 inches greater than the preceding one.
By this arrangement, it will be perceived, is produced a spirally inclined plane of tubes, which are enclosed in a cylindrical case; at the bottom of this the furnace is situated, about one foot beneath the lowest ends of the tubes, and occupying the whole area of the circle. The upper ends of the range of tubes open into a strong receptacle, being secured in both in a thoroughly steam-tight manner, by means of hollow screwed bolts, with nuts and collars, in the following manner:-
A small tube is fixed to the end of each of the spiral tubes, and each of these small tubes is passed through the receptacle, and the shoulder formed by the ends of the large tubes are, with suitable packing interposed, brought, by means of screwed nuts, close up to the side of the receptacles: these receptacles are strong tubes, elliptical in their transverse section, and flattened at their conjugate axes, for the convenience of screwing up firmly. For removing the deposit from the water at pleasure, solid plugs are screwed into the ends of the small tubes, which can be taken out whenever required for that purpose. By the arrangement described, it will appear that the heat from the circular fire, about 4 feet 6 inches in diameter, impinges vertically upon a similar extent of the boiler above; thence ascending the current winds round between the coils of the inclined plane of tubes, which forming the flues as well as the boiler, the heat is abstracted in its progress, by an economical consumption of fuel, through the small spaces between the concentric spirals, the heated air and flames escape out of the spiral current, and by completely enveloping the tubes, materially augment the production of steam.
To increase the combustion, an exhausting fan-wheel is placed immediately over the boiler, revolving on a vertical spindle, which passes through the centre of the boiler and furnace, and is actuated by suitable gear put in motion by the engine. To avoid the inconvenience that might be experienced from the escape of the gaseous products of combustion upwards, the patentees propose to dispense with the use of a chimney, and by enclosing the upper part of the fan-wheel, and surrounding the boiler with an external casing, cause the vapours to pass downwards against the ground, underneath the vehicle.
The patentees likewise propose to force a mixture of highly rarefied steam and heated air through the ignited air in the furnace along a pipe, that makes several coils around the ash-pit, before entering a chamber immediately beneath the great bars; into this chamber by another pipe is also introduced steam, the mixed air and steam from this chamber proceed through a series of short vertical tubes and the hollow bars of the grate, and thence through certain perforated nozzles into time fire in minute jets.
In the centre of the boiler is situated the float chamber; this is of a cylindrical form as far as the boiler extends; but the lower portion, which passes through the furnace, and the bottom of the grate, is tapered off to a reduced diameter, making, the figure of an inverted frustrum of a cone; to the lower end of this vessel is screwed an iron cap, and the upper end is closed in like manner; passing through both these caps and the middle of the chamber, is a straight piece of tube fixed "stanch" to the caps by screwed nuts and packing. This tube is left open, on the outside of the vessel at both ends, and through it passes the vertical spindle of the fan-wheel, at the lower ends of which is a spur wheel, to which the motion is communicated.
By this tubular passage, therefore, the central situation of the float chamber becomes no impediment to the last-mentioned operation, and the tube itself serves as a guide for the float in its ascent and descent. The float is a hollow air-tight copper vessel, having an opening, to let the tube pass to its centre, to which it is kept by a vertical rod (fixed to the bottom of the float) that passes through a stuffing-box in the lower cap, beyond which it is connected to a lever that operates upon the steam-cock of the engine, by which the pump is worked that feeds the supply-pipe.
Water being forced by the lower receptacle of the boiler, it flows through apertures in the short tubes into the lower ends of the spiral tubes, where ebullition takes place, and the water mixed with the steam is driven upwards through the spiral sheet of tubes. The inclined position of these tubes gives the water a tendency to flow back under the steam; that which is forced on decreases as it ascends, by being converted into steam on arriving at the upper receptacle, the steam, together with a small portion of water, enters the float chamber, where the water falls to the bottom, and supports the float, while the steam passes into the steam-pipe.
When a greater quantity of water is accumulated than is evaporated in the float chamber, a rise of the float will be produced, and a proportionate decrease in the quantity of water pumped into the boiler, occasioned by the communication of the float with the steam-cock of the engine. By this arrangement it will be noticed that the float chamber is also the "separatory," the upper portion constituting a steam reservoir, and the lower portion, which is in the centre of the fire, serves as a supplementary boiler. The steam pipe commences at the top of the float chamber, also is carried down by the side of and contact with the outer casing, and also three or four times round the furnace chamber; forming a protection to the casing, while the steam derives, in consequence, an increase of expansive force.
The whole of the frame and engine is supported upon springs, and to allow of their application to the driving cranked axle, two strong rods are used, each of which in firmly jointed set one end to the frame, and attached at the other end to the cranked axle by bearings, by which the frame is allowed to rise and fall. The guiding operation is produced by means of a little wheel running behind (but centrally between) the two fore wheels, acted upon by a system of levers moved by the steersman. The apparatus consists of two rings of iron, of equal diameter, united truly to each other; to the lower ring is attached by brass bearings, the axle of the guide-wheel, and a branch iron proceeds from the front of the upper ring to the axle of the two fore wheels, where it is connected by two joints, that allow the guide wheel and its bearings to rise and fall freely, but prevents its side motion without moving the two fore wheels.
By turning two handles opposite to the steersman's seat, a vertical spindle communicates the motion to cross levers below, which acting upon two rods connected thereto, and to the opposite sides of the under horizontal ring, the latter traverses under the upper ring, (which has no horizontal motion) and sets the guide-wheel to the required angle to the line of motion to make the turn in the road, in the same manner as setting the rudder to the stern of a boat.
In the drawing of the carriage, those parts that are brought into view, considered in connexion with the foregoing description, will afford the reader a pretty correct notion of the general structure.
The engines are situated in a case underneath the carriage body; one of them is shown dotted in at a, which with its piston rod and connecting rod 1, gives motion to the cranked axle of the running wheels a of the carriage. To stiffen the wheel, there is a stout iron ring bolted to the inside of the spokes, and having arms communicating with a central piece that is fixed to the save. The boiler e is boiled to a strong iron framing, and is contained in a double case; the angular dotted lines across it represent the inclinations from a vertical line of the spiral sheet of tubes; and the dotted lines in the centre are intended to express (which they do but imperfectly) the position and arrangement of the float and steam chamber; f is the guiding spindle and g the steering wheel, surrounded by its two traversing rings, the upper ring being attached by a curved iron arm to the fore axletree, and the lower one to the axis of the steering ached. Between the transit irons of the fore wheels, and the bar to which the guide-wheel is attached, there is a strong spiral spring, acted upon by a screw, to regulate the pressure, according to the state of the roads.
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