Similarity in the general features of construction. - Stephenson's Patent Engines. - Mt-lling's Patent Engines with new Couplings, and Breaks, and Slidevalves. - Tayleure and C'o.'s six wheeled Engines. - On the comparative advantages of four and six wheeled Engines. - Bury and Co's defence of four wheeled Engines, with a " Practical Engineer's" reply thereto. - Remarks thereon. - Experiments on the Grand Junction, and London and Birmingham lines. - Wyndes and Ericsson's improvement for ascending Inclined Planes.- Kollman's LocomotiveGuides. - Prosser's GuideWheels. - Stephenson's compoundAxles. - Losh's Patent Wheels. - Lipscomb's Patent Wheels for preventing Vibration and Noise. - Dirck's Wooden Fellied Wheels. - Mode of fixing Tubes in Boilers. - Water Gauge. - Water Ash-box. - Bergin s .Buffers. - Mallett's Buffers. - Terminus Buffer. - Curtis's safety Passenger Carriage. - Curtis's improved Truck for the conveyance of Carriages. - Booth's Railway Connecters, and mode of checking Speed. - Hick's Locomotive Engine. - Booth's Patent Axle Grease.
Having explained the various arrangements of the railway and its accessories, we now proceed to describe the construction of the several kinds of vehicles which run thereon.
Since the first introduction of railways for passenger traffic by locomotive engines, that is to say, since the opening of the Liverpool and Manchester line, the efficiency of the engines has been greatly augmented; those of the present day transporting much heavier loads at a greater speed, and at a less cost, than the engines of 15 years back. This is owing partly to increased dimensions of the boilers, and the steam cylinders, and somewhat to that splendid accuracy of workmanship and solidity of construction which the keen rivalry of the manufacturing engineers has induced them to put forth: to which may be added many improvements in the details of the machinery; some tending to simplify and reduce friction, others to create new effects and so increase efficiency. Nevertheless, in the principal combinations, and the general features of the whole structure, there is a certain similarity, which while it attests their relationship, distinctly shows the intellectual training to which they have been submitted by the mechanists of the present day.
The boiler is almost universally composed of a vertical compartment (square or cylindrical in its horizontal section), containing within it the furnace, (now designated the "fire-box,") surrounded by water; this vertical compartment opens into a horizontal cylindrical chamber, containing the greater portion of the water, which is heated by the gases and flames proceeding from the fire, through an extensive series of small tubes of thin metal, lying horizontally in parallel straight lines throughout; one end of every tube being open to the fire, to receive the heated current, and the other end opening into a vertical "smoke box," at the other extremity of the horizontal cylindrical chamber. Into this smoke box is discharged all the smoke and gaseous products of the combustion, which escape in a rapid current, excited by a blast produced by the escape of the eduction steam into a small chimney, erected immediately over it. The requisite supply of fuel for the journey, and of water for evaporation, is carried by a judiciously contrived machine called a tender, which is linked close to the engine.
The principal diversities in the construction are to be found in the number and position of the wheels; in the description of the framing, which sometimes extends outside the wheels, and sometimes lies within them; and in the position of the steam cylinders, and the mode of connecting them with the shaft of the driving wheels. In some engines the steam cylinders are placed in the smoke box, and the connecting rods transmit the force to two cranks, forged at right angles to each other, near the middle of the axle of the driving wheels; whilst in other engines the steam cylinders are placed outside the frame, the driving shafts are straight, and the connecting rods are attached to cranks fixed on each end of the shaft, or to pins in the bosses of the wheels. In the early part of the working of the Manchester and Liverpool railway, the locomotive engines were generally constructed with a double cranked axis upon the two main, wheels of the carriage; which wheels were provided with flanges on their peripheries to keep the engines on the rails.
But this mode of construction was considered by Mr. Stephenson to be defective, owing to the liability of the crank axis becoming strained or broken by the excessive friction of the flanges against the rails, especially in making deviations from the straight course Any lateral bending of the cranked axle, although short of a fracture, will, it is evident, by putting the wheels out of square, produce a violent surging motion of the engine, and render a fracture of the axle, or the running of the engine off the rails, extremely probable. To provide a remedy for such serious liabilities, Mr. R. Stephenson, under his patent of 1833, divested the tires of the main impelled wheels of their flanges, and in lieu thereof, employed two small additional wheels with flanges behind the former. These additional wheels were applied beneath the fire-place end of the boiler, for keeping the engine straight on the rails in its progress forward; and the axles of these wheels being straight, and consequently stronger than the cranked, are not liable to be broken or bent, as experience has proved with respect to the axes of the fore wheels, which remained unaltered.
The engines made by Mr. Stephenson to carry out these improvements we shall now proceed to describe with reference to the annexed cuts, designed to illustrate the same. At K K are main impelled wheels on the cranked axles, without any projecting flanges on the tires, which run on the edge rail9 L. M M are the additional small wheels with flanges, applied beneath the furnace end of the boiler; and O are the ordinary small wheels with flanges beneath the chimney end of the boiler, where the working steam cylinders are situated. The small wheels O and M with flanges, keep the engine straight upon the rails, and the large impelled wheels K have only to advance the engine, and to bear a due proportion of the weight. By this arrangement, therefore, the cranked axle is liberated from all lateral strain, which is wholly transferred to the small wheels with flanges, which, having straight axles, are capable of sustaining it.