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On the 3d of February, 1824, a patent was granted to T. Birstall and John Hill, of Leith, for a locomotive steam carriage; an account of which was first given in the Edinburgh Journal of Science, whence we derive the following description.
"A represents the boiler, which is formed of a stout cast-iron or other suitable metal flue, enclosed in a wrought-iron or copper case, as seen in section, where A is the place for fuel, and a-a-a are parts of the flue, as seen in section, the top being formed into a number of shallow trays or receptacles for containing a small quantity of water in a state of being converted into steam, which is admitted from the reservoir by a small pipe.
“B is the chimney, arising from the centre flue; at D are the two cylinders, one behind the other, which are fitted up with pistons and valves or cocks, in the usual way, for the alternate action of steam above and below the pistons. The boiler being suspended on springs, the steam is conveyed from it to the engines, through the helical pipe c, which has that form given to it to allow the vibration of the boiler, without injury to the steam joints.
“E is the cistern containing water for one stage, say 50 to 80 gallons, and is made of strong copper, and air-tight, to sustain a pressure of about 60 pounds to the square inch. At e are one or more air-pumps, which are worked by the beams F-E of the engines, and are used to force air into the water vessel, that its pressure may drive out, by a convenient pipe, the water into the boiler, at such times and in such quantities as may be required.
“The two beams are connected at one end with the piston rods, and at the other with the rocking standards H-H. At about one-fourth of the length of the beams from the piston rods are the two connecting rods g-g, their lower ends being attached to two cranks, formed at angles of 90 degrees from each other on the hind axle, giving, by the action of the steam, a continued rotatory motion to the wheels, without the necessity of a fly-wheel.
“The four coach wheels are attached to the axles nearly as in common coaches, except that there is a ratchet wheel formed upon the back part of the nave, with a box wedged into the axle, containing a dog or pall, with a spring on the back of it, for the purpose of causing the wheels to be impelled when the axle revolves, and at the same time allowing the outer wheel, when the carriage describes a curve, to travel faster than the inner one, and still be ready to receive the impulse of the engine as soon as it comes to a straight course.
"The patentees have another method of performing the same operation with the further advantage of backing the coach when the engines are backed. In this plan, the naves are cast with a recess in the middle, in which is a double bevelled clutch, the inside of the nave being formed to correspond. The clutches are simultaneously acted upon by connecting levers, and springs, and which, according as they are forced to the right or left, will enable the carriage to be moved forward or backward. To the fore nave are fixed two cylindrical metal rings, round which are two friction bands, to be tightened by a lever convenient for the foot of the conductor, and which will readily retard or stop the coach when descending hills. K is the seat of the conductor, with the steering wheel L in the front, which is fastened on the small upright shaft l, and turns the two bevel pinions 2, and the shaft 3, with its small pinion 4, which working into a each on the segment of a circle on the fore carriage, gives full power to place the two axles at any angle necessary for causing the carriage to turn on the road, the centre of motion being the perch pin I.
"The fore and hind carriage are connected by a perch, which is bolted fast at one end by the fork, and at the other is screwed by two collars, which permit the fore and hind wheels to adapt themselves to the curve of the road. To ascend acclivities, and particularly where the carriage is used on railways, or to drag another behind it, it is presumed that greater friction will be required on the road than the two hind wheels will give, and there is, therefore, a contrivance to turn all the four wheels. This is done by a pair of mitre wheels 4, one being on the hind axle, and the other on the longitudinal shaft 6, on which shaft is a universal joint, directly under the perch pin I, at 7. This enables the small shaft 7 to be turned, though the carriage should be on the lock. On one end of she shaft 7, is one of a pair of bevel wheels, the other being on the fore axle, which wheels are in the same proportion to one another as the fore and hind wheels of the carriage are, and this causes their circumference to move on the ground at the same speed. The engines were calculated at ten horses' power, and it was purposed to use steam of the highest pressure, which was to be let off into a separate vessel, and the quantity emitted to be regulated by one or more cocks."
"From the foregoing description," (observes the editor of the before-mentioned journal) "we think we are warranted in saying, that there is considerable degree of ingenuity, as well as originality, in many of the details, and also in the general arrangement of the machinery. In this light we regard their mode of allowing the several wheels to move simultaneously at different velocities; the convoluted form given to the steam and water pipes, by which the injurious effects of jolting are avoided by very simple means; and the mode of injecting water into the boiler by means of compressed air."
"By the present improvements, the boiler is to be placed upon an additional pair of wheels, so that the whole machine may run upon six wheels instead of four. The patentees claim two distinct modes of employing this extra pair of wheels, either of which may be adopted. By the first mode, the back end of the boiler is bolted to the axletree of the extra wheels, and the front end rests and turns upon a pivot, fixed to the axle of the middle pair of wheels. By the second mode, the axle of the hind wheels turns upon a centre, and the boiler is attached to a frame, which encompasses it; this frame is suspended upon springs or not , according to the nature of the road, the part of it being bolted to the axle of the middle pair of wheels. By either of these contrivances, the carriage containing the boiler may be made to adapt itself to the bends in the road, without incurring injurious strains.
“The next improvement of material importance consists in the construction of the steam pipes, which have sliding and movable knee-formed joints, to admit of their extension and contraction, when the carriage is passing over rough or undulating ground; thus constructed, the pipes also accommodate themselves to bends and irregularities in the road.
The third improvement relates to the mode of steering the carriage, whirls is effected by a chain circumscribing the steering wheel the ends of the chain then passing round pulleys fixed to the carriage frame, are attached to the opposite extremities of the fore axletree."
Shortly after the publication of the foregoing announcement in the Edinburgh Journal of Science, We had an opportunity of inspecting a working model constructed upon a scale of three inches to the foot, which embraced these improvements. It was publicly exhibited in Edinburgh and afterwards in London, where it was made to travel round a circle of 17 feet diameter, on an uneven deal floor, with a speed equal to about 7 miles per hour. A deal platform, 18 feet long, rising 1 foot at the end (or 1 in 18) was fixed, which the carriage ran rapidly up without apparent effort. On the outside of the circle was a deal bank which rose 5 in 25, in the cross section, which was used to show that there was no liability of upsetting the carriage even by such uneven ground, owing to the position of the centre of gravity being very low.
The representation of this model and the description of the machine, we extract front the Register of Arts published at that period.
"The length of the model is 5.5 feet, and its height 22 inches. The steersman sits in front, and by turning a circular horizontal plate c gives the first pair of wheels a direction to the right or the left, as may be required. The boiler is of a conical form, and is supported by an iron frame, extending from the second to the third pair of wheels. The fire is in the middle of the cone, and the water and steam outside. The engines are of the high pressure kind, and the boiler is of copper, calculated to sustain ten times the force of the intended working pressure of the steam. Two cylinders are employed, they occupy the hind boot, and rest on the axle of the middle wheels; in the model the cylinders are three inches in diameter, and have a three-inch stroke. The cistern is at a, whence the water is pumped by the engine, and forced into the boiler; e is the induction steam pipe, i the eduction pipe, leading to the chimney, wherein the waste steam being expanded by the heat, escapes invisibly, while it increases the draught, and combustion of the fuel.
“When the writer saw this interesting model at work, he was informed by the partner of Mr. Burstall, that it had, during the preceding eight days, ran as many times round its circular course as amounted to 250 miles; and that during all that period it required no fresh packing or repair whatever.