Engineers and Mechanics Encyclopedia 1839: Railways: Development of Edge Rails
This is an assortment of paragraphs from various part of the section on railways.
The origin of edge-rails cannot easily be traced. The wooden rails partook of this character; for they were generally rounded a little on their upper surfaces, and flanges were put upon the peripheries of the wheels, which, projecting downwards over the sides of the rails, kept the wheels in their tracks; and in some cases, square wrought-iron bars were fastened over the wooden rails, partly with a view to strengthen them, as well as to form guides to the wheels and the transition to improved forms was therefore easy. In 1789, Mr. Jessop introduced a cast-iron edge-rail in the public road at Loughborough, the upper surface of which was flat, and the strider of an elliptical shape.
It has been repeatedly proposed of late years, to form a rail, or iron way, upon a portion of the common public road, so as not to rise above the level of the general surface, and thus permit carriages to cross them in any direction, without impediment. The utility of the principle of this arrangement has for some time past been demonstrated by the excellent granite stone-way for waggons, in the Commercial Road, and the adoption of the same plan in Friday-street, and other parts of London; for by these rough structures, the effect of horse-power is at the least doubled, or one horse is saved out of every two. If too much has been gained by to slight an improvement of the surface; what may not be expected when ignorance and prejudice shall permit the introduction of such perfect surfaces as iron will afford?
There is, however, too need of conjecture in the matter; the results of the actual work upon the Liverpool and Manchester Railway show us, that a force of draught equal to a weight of one pound descending from a pulley, is capable of drawing 200 lbs. upon the rail at 21 miles per hour, which is the ordinary pace of a cart horse, whose power of draught through a day's work is estimated at 150 lbs. drawn up over a pulley at the same velocity. Consequently, we have 150 x 200 = 30,000 lbs.; or between 13 and 14 tons, drawn by one horse with perfect ease!
Whatever admiration such effects might excite in the public mind, they would create no surprise to persons at all acquainted with mechanical science; indeed, it appears from experiments made by Mr. Wood, with a well constructed model, that the whole of the resistances to the motion of a carriage upon a level railway are capable of being reduced to the five hundredth part of the weight; consequently one horse would be competent to draw (500 x 150 = 75,000 lbs., or upwards of 33 tons!
But it is not to be expected that the accuracy of workmanship in a model could be carried into effect, or the expense of it afforded on the great scale; nevertheless, when the numerous little progressive ameliorations which the present extensive practice of our railroad mechanic are daily developing, are taken into account, it scarcely admits of a doubt that a horse may be rendered capable of drawing, at the least, 20 tons.
The important improvement effected on the Penryhn Railway, by Mr. Wyatt, described at page 381, naturally led to ameliorations in the structure of similar works elsewhere, which was especially observable on the banks of the Tyne and Wear. The expense of the transit of coals forms so considerable a proportion of their money cost, that the owners are always alive to any decided saving that may be effected therein.
In the engravings in page 385 (above), Fig. 1 represents a side view, Fig. 2 a plan, and Fig. 3 a cross-section of a cast-iron edge-rail, of the form which has been extensively adopted in the districts above mentioned. The waggons run upon the rounded edge of the rail, which is smooth, and laid an evenly and regularly as possible. The length of these rails is usually three feet, with a depth of about four inches and a half in the middle, and breadth of the top two inches; but in some railways the rails are four feet long.
The ends of the rails meet in a piece of cast-iron, called a chair (see Fig. 4), and the chairs are fixed to stone blocks or sleepers, with a broad base, and weighing from one and a half to two hundred weight. These are firmly bedded in the ground, and adjusted to a proper plane for the road before the chairs are connected to them. The goodness of the road of course depends much on fixing the sleepers in a sound, firm manner.
In Fig. 1 the side view of the rail C is shown, supported at the extremities A-B by cast-iron chairs E-E, which rest on blocks of stone D-D, called sleepers. Fig. 2, the plan, shows the scarf joints, where the ends of the rails meet in the iron chairs E-E. Fig. 3, the cross section of the rail taken at C, in Fig. 1, which is the middle of its length. Fig. 4 is a cross section at B, through the joint chair and supporting blocks.
Up to the period to which our present history of railways relates, it does not appear that any other power of draught or propulsion was employed but that of horses, and, occasionally, of fixed engines up inclined planes.
From all the information that we can glean in tracing out the early history of locomotion, this remarkable circumstance constantly presents itself, - that when Trevithick's carriages with smooth wheels were employed upon levels, or slightly inclined planes, invidious comparisons with others having cogs were made against the former, because, as was asserted, they slipped and could not ascend such acclivities as the latter; and this, notwithstanding Trevithick first suggested by his “cross grooves and fittings to railroads" the very principle of the cogs, in a less objectionable form, and "all other appliances to boot" of the engine and boiler, contained in the said locomotive!
Thus Trevithick lost many orders, and they were given to those who adopted all the essentials of his plans, without acknowledgment, and employed them as the basis of their structures. And when, after the lapse of years, it was found out by these gentlemen that smooth wheels had sufficient "bite" of the rail in most circumstances, they made that fact appear to be their own discovery; notwithstanding it is stated in Trevithick's specification of 1802, and was confirmed by his practice; which practice they at first condemned with one general voice; and when, at last, they were compelled to practise it also, they endeavoured to make it appear as vastly superior to Trevithick's mode of surrounding his wheels "with heads of nails, bolts, and claws," which he never used at all!
These ungenerous proceedings against the most eminent mechanic of his time appear to have been going on unchecked from 1802 up to the present time 1838. The only way we have of accounting for this circumstance is, that Trevithick was engaged during many years of his patent right in constructing his high-pressure engines and pumps for recovering the drowned mines of Peru, which undertaking be afterwards personally directed, and succeeded in accomplishing, to the astonishment of the Peruvians. He was subsequently appointed engineer to the royal mint at Lima; and on his arrival at South America, he was received with such enthusiastic gratitude, that the lord warden proposed to "erect his statue in silver."
The earth now covers the mortal remains of this eminent man; but his memory will never die: for, to use the words of Mr. Gordon, he has left behind him "a name as inseparably connected with high-pressure steam and locomotion, as that of James Watt with the condensing engine and rotary movement."
We have already observed, in the foregoing part of this article, that in the earliest constructed railroads, which were chiefly confined to a descending trade, from the coal mines to the shores of the neighbouring rivers, very little attention was paid to the formation of planes of uniform inclinations; and the latter were seldom so great as to render it difficult to draw up the empty waggons on their return.
Very abrupt acclivities were partially levelled, and deep chasms and ravines only filled in: consequently, the power which the horses had to exert on the same line of road fluctuated considerably. In some parts the animals were overworked, and in others they were an encumbrance; so that it often became necessary to unhook their traces, and let them follow the waggons, which descended simply by their own gravity.
For a long period, the horse was the only power used upon railways. To this succeeded the application of the power of gravity, to cause a descending heavy body to raise a lighter up an opposite inclined plane, a process which had previously been employed upon canals, in drawing the empty boats out of the water on to a higher level, by means of the descent of the loaded boats down the declivity. But a little consideration will show that this kind of power can only be resorted to in peculiar circumstances and situations.
It is only where a preponderance of goods has to be conveyed in one direction, and where, upon any declivities occurring in the line of road, that preponderance is capable of overcoming the gravity of the returning carriages, that the action of gravity can be used to advantage. It is, therefore, of importance, to ascertain upon what declivities, with a given preponderating load, this power is available; the object of all such inclined planes being to convey down a certain quantity of goods in a given time, and to do this with the least expenditure of power.
In forming a railroad, therefore, with the view of using this species of traction, it is not only necessary that the descent of the plane be such as to give a preponderance to the loaded carriages over those which are empty, but such a preponderance as still cause them to descend, and drag up the empty carriages with the requisite velocity. For if we give to the plane a greater degree of inclination than requisite, we expose the rotors and carriages to an unnecessary strain, and consequently to additional wear and cost; and if the inclination be not sufficient, the proper performance will not be accomplished. The laws which govern bodies descending inclined planes have been very ably developed by Nicholas Wood, in his Practical Treatise on Railroads, accompanied with such illustrations as will render the subject a matter of easy calculation to those of our readers who may be interested in the subject; to which work we have, therefore, great pleasure in referring them. We shall, however, here avail ourselves of the description given by that eminent engineer, of the manner of working self-acting inclined planes in the neighbourhood of Newcastle-upon-Tyne.
The annexed figure represents a ground plan of the wheel w-w of a self-acting inclined plane, round the rim of which the rope winds, by which the loaded carriages drag the empty ones up the plane. The wheel is generally of cast-iron, about six feet diameter, with six spokes, and a grooved rim for the rope to wind upon, the groove being only of sufficient width to hold the rope within it as the wheel moves round; consequently the rope, when in action, only passes round one half of the wheel, from a to b. At the top of the plane, a square hole is dug, the sides of which are lined with masonry, the top being nearly upon the same level as the railroad; the wheel is then placed between two frames of timber, the upper of which, a-b and c-d are shown in the drawing. They are kept steady by the diagonal braces e-e.
The carriages on which the axle runs are placed on the front of these frames; the upper one at g, and the other immediately below it, on which the ends of the axle that sustains the wheel rest, and on which it is at liberty to run freely round. At the top of the inclined plane, a certain space of ground, for about twenty or thirty yards, (varying according to the number of carriages run down at a time,) is made nearly level, on which the loaded carriages remain until they are to be lowered down, and on which the empty ones stop after their passage up the plane; at the end of this level, or slightly inclining ground, furthest from the top of the plane, the wheel is placed, and small horizontal sheeves s-s-s-s-s-s are placed in the direction the rope runs, to prevent its being injured by dragging along the ground, and also to diminish its friction. These horizontal sheeves are placed at intervals of every eight or ten yards upon the plane from one end to the other.
The drawing will show the periphery of two kinds; the one being flat, and the other circular, and of a width just sufficient to admit the rope upon it; their diameter about eleven inches, with a flange on each side to prevent the rope from running off: they are made most frequently to run upon pieces of wood, and sometimes upon cast-iron stands, placed upright upon the middle of the road; the axles are made of wrought-iron, and where they run upon the upright bearings, about three quarters of an inch diameter.
The plane is then made into a proper slope, between the platform or level upon which the wheel is placed, and the lower extremity, when a similar flat or piece of level road is made, for the descending train of waggons to land upon. The slope is either uniform, or such as the nature of the ground will permit. Sometimes it is necessary to make considerable bends or curves in the line of the road; but whatever be the form or length of the slope, it must always be terminated at each end by these flat platforms. The narrow parallel lines in the drawing will show the rails as laid down upon the platform; the wheel being placed below the level of the rail, the square hole is covered up, and the rails pass over upon the cover.
In the drawing, the rails are broken off at k-k, the cover being removed to show the wheel. The dotted line A-A, may be supposed to represent the one end of the platform, and the top of the plane. Three rails r-r-r are laid from this part nearly half way down the plane, of the requisite width between each rail, for the carriages to run upon, so that both the ascending and descending train pass upon the middle, and upon one of the outer rails; these are continued to where the one train of waggons have to pass each other. The three rails, then made to branch into four in the same manner as A-A to B-B, for a certain distance, sufficient to allow the carriages to pass each other; these four rails then converge into two, or a single line of road, as shown at c-c, and are so continued to the bottom of the plane, so that parallel lines, as shown in the drawing, will represent a complete passing.
The empty, or ascending carriages will be at c-c when the loaded carriages are at A-A, and they will pass each other between K and B-B'. In this form of plane, it will be seen, that the loaded carriages pass alternately down the sides D and E. For instance, if they commence their descent at D, one end of the rope being attached to them, and the other end being at E, at the foot of the plane, and fastened to the empty carriages, the loaded carriages will pass down D, and when they arrive at the bottom, the empty ones will arrive at the top, at E.
Upon the other side of the-plane, the loaded carriages, in the next operation, pass down the side E of the plane, and the empty ones up D. When used for passing boats from one level to another upon canals, and also on several railroads, a double line of road is laid from top to bottom of the plane, with a double line of rollers or sheeves; but the reader will perceive, that in most cases, the one above described will answer precisely the same purpose. In very short planes the obliquity of the road, in passing from a double to a single line, will cause a retardation to the carriages, and also additional friction to the rope but upon long planes this is scarcely felt, and the cost of a double road the whole distance would be considerably greater.
When the slope of the plane is not uniform, descending more rapidly in some parts than in others, or when the descent is so great as to give more than a requisite preponderance to the moving power, a brake is applied to the periphery of the inclined wheel, to equalize or regulate the seniority of the carriages down the plane; and, in many instances, men traverse the plane with each train of waggons, and apply the brake or convoy of the carriages to check. their velocity, when required. The brake upon the inclined wheel will be perceived to have no power in checking the velocity of the carriages more than what is equal to the hold the rope takes upon the wheel in. passing round its semi-periphery; for if the excess of gravity of the loaded carriages, above what is required to overcome the whole retarding forces, be greater than the hold of the rope' the wheel may be completely stopped, and the rope slide round the wheel, which in some instances, might be attended with danger. The declivity of the plane should never be so great as to cause such an excess or preponderance of gravity, when such a wheel as this is used.
See Also
Sources of Information