In this method the wheels of the waggons cannot be obstructed by the heads of the nails rising above the surface, and the blocks are not disturbed by fixing the plates; and when repairs arc necessary, the plates must be formed for the purpose. When tram-plates are fixed by spikes to stone sleepers, there is some difficulty in keeping the joint even and in its place; but it seems to be successfully obviated by using a saddle-pin to receive the ends of the nails at the joints, an improvement which was introduced by Mr. Wilson on the Troon tramroad.
Tramroads are much esteemed in Wales; and in consequence of using them, it is found desirable to divide the pressure upon the rails as much as possible; hence, small carriages are used, and these lead to small wheels, so that the effect of a given power is not above half what it ought to be; and yet the enormous increase of railroads in Wales renders it evident that some benefit is received from adopting this system of conveyance. In 1791, there was scarcely a single railway in South Wales; and in 1811, the complete railroads connected with canals, collieries, etc. in Monmouthshire, Glamorganshire, and Caermarthen-shire, amounted to nearly 150 miles in length, exclusive of under-ground ones, of which one company in Merthyr Tydvil possessed about thirty miles; since which period the lines have been extended to, at the least, five hundred miles.
It now becomes proper to introduce some notice of edge rails, the use of which is so generally and justly preferred to the tram plate. Their origin it would be difficult to trace with any precision; and it is a question of so little moment, as to be hardly worth the trouble of investigation. Some of the wooden rails partook of the usual shape, especially when capped with a plate of iron: hence a transition to more judicious forms and more permanent materials was easy.
The earliest complete edge rail which we know of was made of cast-iron, in 1789, by Mr. Jessop, at Loughborough, the upper surface of which was flat, and the under of an elliptical shape. But this appears to have been so little known to engineers, that we find Mr. Benjamin Wyatt making use of a cast-iron edge rail in 1800, and imagining himself to be the inventor. The form of his rail was indeed quite original, and ought not therefore to be omitted in this sketch. It is thus described by himself:previously performed by 144 carts, and 400 horses: so that ten horses will by means of this railway do the work of four hundred!
"The rail hitherto made use of in most railways is a flat one, 3 feet in length, with a rib on one edge, to give it strength, and to prevent the wheels, which have a flat rim, from running off. Observing that these rails were frequently obstructed by stones and dirt lodging upon them; that they were obliged to be fastened to single stones or blocks, on account of their not rising sufficiently above the sills to admit of gravelling the horse path; that the sharp rib standing up was dangerous for the horses; that the strength of the rail was applied the wrong way; and that less surface would produce less friction: led me to consider if some better form of rail could not be applied. The oval presented itself as the best adapted to correct all the faults of the flat rail, and I have the satisfaction to say that it has completely answered the purpose in a railway lately executed for Lord Penrhyn, from his lordship's slate quarries in Caernarvonshire to Port Penrhyn, the place of shipping. The wheel made use of on these rails, has a concave rim, so contrived in its form, and the wheels so fixed upon their axes, as to move with the greatest facility on the sharpest curves that can be required." In the annexed section, a represents the rail, which is 2 inches deep and l 1/2 inch thick horizontally; the lower part, b, is cast to each end of the rail, 3 inches long, to let into the sills, which have a dove-tailed notch to receive them.
The advantages of this form were said to be, that no dirt can lodge upon it; that it is strong for its weight, and calculated to resist both the lateral and perpendicular pressure; that it must occasion but little friction; that it may be placed on the sills so as to admit a sufficient quantity of gravel to cover them, and present no danger to the horses. They were cast 4 feet 6 inches long, and weighed 36 pounds each.
The Penrhyn railway is six miles and a quarter in length, divided into five stages. It has three-eighths of an inch fall in a yard, with three inclines; was begun in October 1800, and finished in July 1801. The annexed sketch shows the kind of waggons that were used on this railway, twenty-four of which, containing 24 tons, were drawn by two horses (one stage) six times a day; which is 144 tons per day. drawn 61/4 miles per day. This quantity of work was
It was however found that the oval-formed rail had a tendency to wear the concave rims of the wheels very fast into hollows, which fitted so tight upon the rail as to create great friction, and render it necessary to change the wheels very often. It was accordingly proposed to substitute for them a rail and wheel represented in the annexed cross section: a is the rail, b the dovetail, c the lower ends of the wheels, and e the sills, now made of cast iron.