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But, if we round off these edges, as in fig. 4, it is equally apparent that this splitting tendency must be materially diminished, inasmuch as the cohesion of a much more extended area must be overcome, before a piece can be separated.
I have universally observed so much less splitting in such rails as are boldly rounded at the top edges, than in those whose edges were comparatively sharp, that I have no doubt but that a still further extension of the same principle would be found to contribute considerably towards a correction of the evil, even if no very great improvement should be made in the welding.
Many of our railroads have rails of the section, (fig. 5,) the upper edges of whose top are dissimilar, one being boldly rounded, while the other is left comparatively sharp. Such rails elucidate my views on this point in a very satisfactory manner; for I have observed that, in every instance, after having been for some time traversed by heavy engines, the outer, or sharp edge splits off badly, while the rounded, or inner one remains comparatively uninjured. Consequently, this section of rail is objectionable, and I hope soon to see it fall into disuse. It was originally projected to save metal in the outer lip; but I am confident that the pecuniary advantage resulting from any such saving, is far more than countervailed by the diminution of strength attending it.
Moreover, there is another disadvantage attached to this section of rail, which is, that when the inner lip becomes worn away, as it will in time, especially on the outer lines of curves, the rail cannot be turned so as to make the original outer lip answer for the inner one. This turning of the rails I have frequently seen resorted to on the sharp curves of much-used railroads, and the rail should, by all means, be made with a view to this facility.
A bridge, or inverted U, rail, with the edges well rounded, as in this figure, (6,) will, I suspect, be found to resist splitting better than any form of section in present use; inasmuch as it not only presents a great extent of area of cohesion to be overcome before splitting can take place, but affords less leverage for the weight of the engines to act through to overcome it. In some cases,
I have seen the T rail split in this manner, (fig. 7,) which proves that, in this section, the welding may, from want of care, be so very imperfect, that no rounding of the edges, alone, could prevent injury. Such disruptions as this, evince very clearly, the utility of diminishing the leverage through which the disrupting weight may act.
The ordinary flat-bar furnishes strong evidence of the diminution of splitting arising from more perfect welding, combined with the
parallelism of the lamina with the top and base of the rail, aided by an absence of leverage; for it will be found, on examining such of our roads as are laid in part with the flat-bar, and in part with the T rail, that unless the latter be of an unusually strong pattern, it has split much more than the flat-bar.
The foregoing remarks will, I trust, sufficiently explain my reasons for not conceiving the splitting of the rolled rails to be attributable to any defect inherent in the nature of the material itself, but to other causes, which admit of easy remedy; and that, therefore, the principal argument adduced against the rolled rail, is not a tenable one.
Before I conclude this part of our subject, I will advance one suggestion, depending on the propriety of rounding more boldly the top edges of rails, that may possibly be of service on some of our railroads, on which the pattern for the rail to be used has not yet been decided on. It is this, that while we have been gradually increas ing the weight of our rails, we have unfortunately overlooked the important consideration, of applying the additional metal to the place where it is most needed.
In consequence of this oversight, it will be found that some of our heavier, improved (?) rails, split to pieces sooner than some of the lighter ones have done, whose upper table was stouter, and better rounded.
I have had occasion to notice this more rapid deterioration of heavy rails, consequent upon want of just proportion in their parts, in more instances than one, upon very important lines of communication.
Another suggestion, having reference to the weight borne by the drivers of our engines, may not be deemed unimportant.
It is plain that, so long as we retain a top width of rail of about 24 inches, we cannot safely place, upon any one driving-wheel, a greater load than can be sustained without crushing, and splitting, by the ends of the rails, upon that width; otherwise the ends of the rails must be crushed, as shown in fig. 8. I shall do no more than allude to this point; my reason for introducing it is, that I feel very confident, from observation, that we have already, in some cases, exceeded the proper limit of load on a driver, warrantable by a top width of 24 inches.
The success which appears to attend the new six-driver freight-engine of that enterprising and skilful machinist, Matthias W. Baldwin, of this city, will go far towards arresting the destruction of our rolled rails. With a weight of but about two tons resting on each driver, she draws, with ease, trains weighing 200 tons over the 45 feet ascents on the Philadelphia and Columbia railroad; and the writer has seen her start, with apparent ease, a train weighing about 150 tons, up grades of 36 feet per mile, when the rails were in an unfavorable condition, being dusty, and slightly wet by a drizzling rain, which began to fall just at the time.
An increase in the number of drivers to our locomotives, which will enable us to diminish the weight borne by each, while, at the same time, it increases the total amount of adhesion, thus enabling us
to draw heavier trains with less injury to the rails and other portions of the superstructure, I look upon as the greatest desideratum demanded, at the present day, towards perfecting the railroad system.
The advocates for cast-iron rails appear to conceive that material to be free from the danger of splitting on its upper edges, found so objectionable in our present rolled rails. But this is an error; for, unless the upper edges of the cast rail, also, be well rounded, they will be found to be fully as liable to that defect as the rolled rail. The pieces split off will not, it is true, be so long as those which separate from the rolled rail, owing to the granular structure of cast-iron; but their greater number will more than compensate for their difference in length.
From the observations I have made on rails of this material, I find that the splitting, in the case of sharp-edged rails, takes place on the outer edge to a greater extent than on the inner one; and for this reason: the friction of the flanches against the inner edge of the rails has a tendency to wear that edge gradually into a curve, conformable to that which unites the flanch to the tread of the wheel; and this curve operates as a partial protection against splitting, on the principle already alluded to, when speaking of the upper edges of rolled rails.
'This action is particularly observable in the outer rails of sudden curves, where the inner edge soon becomes smoothly worn to a bold curve, which acts as a complete preservative against splitting, while the outer edges of the same rails become much injured. On straight lines, the splitting under heavy engines is very serious on both edges, if they be not well rounded; but it is perceptibly greater on the outer one. I have observed the same protective tendency of the outward pressure of the flanches very sensibly exhibited also in some rolled rails which have sharp edges.
By rounding off the edges of the cast rail about as boldly as is done in our best heavy rolled rails, and at the same time diminishing the weight borne by any one driving-wheel to about 1 tons, I think we should prevent either splitting, or very serious abrasion; and I should not hesitate to employ such a rail, under such circumstances, whenever important considerations should happen to demand it.
We will now glance rapidly at two of the principal objections urged against the cast-iron rail, viz., its brittleness, and its more rapid
Admitting, of course, the former objection, the friends of the cast rail propose to obviate it by the use of continuous wooden bearings. But this expedient, although unquestionably effective so far as it removes the danger of the rails breaking, will, on calculation, be found, in many cases, to raise the cost of the cast-iron track to an equality with one of rolled iron, in which the continuous bearings are not employed; and especially will this remark apply if the bearings be Kyanized.
This consideration neutralizes, in a great measure, one of the principal arguments in favor of the cast rail, viz., its comparative cheap
But, in cases where it is determined either to adopt, or to dispense with, bearing timbers, whether the rail be cast, or rolled, there the proportion of expense is entirely in favor of cast-iron; even when the latter has given to it an increase of weight over that of the former, sufficient to impart to it an equality of strength.
As to the wear of cast-iron rails, it cannot, I think, be denied that it is much greater than that of the rolled rails. According to experiments cited in "Wood on Railroads," the comparative wear is shown to be about as 4 or 5 to 1.
He says, (see 3d London edition, page 67:)
"We shall now give some of the results of the wear of cast and wrought-iron rails, with a view of determining the depth of bearing surface.
"In the former edition of this work, we gave an account of two experiments, on the wear of cast and wrought-iron rails, upon the Stockton and Darlington railway, as follows:-Malleable-iron rails, 15 feet long, over which locomotive engines pass, weighing from 8 to 11 tons; wagons loaded, 4 tons each; 85,000 tons passed over in a year, exclusive of engines and empty wagons; weight of rail, 1361⁄2 pounds; loss of weight, in 12 months, 8 ounces; the breadth of the top of the rail, being 24 inches, gives one-tenth of a pound, per yard, per annum; and Mr. Story informs us that subsequent experiments furnish nearly the same results. In determining the premium for the best form of rail, for the London and Birmingham Railway Company, with Professor Barlow and Mr. Rastrick, we found the annual wear, estimated by some of the competitors, at one-sixth of a pound, per yard, per annum. Upon the Killingworth railway, I have had some of the rails, which were weighed and laid down in 1825, taken up and re-weighed; and find the average loss of weight of several rails, to have been eight pounds, for each 15-feet rail, in 12 years, which gives about one-eighth of a pound, per yard, per annum. These rails were laid down at a time when the manufacture of malleable-iron rails was not so well understood as at present; and, on examination, I found part of the loss of weight was attributable to exfoliation on the sides. About 100,000 tons of coals would pass over these rails annually, exclusive of the weight of the engines and empty carriages. Mr. Dixon, the resident engineer upon the Liverpool and Manchester railway, states the wear of the rails upon that railway to be one-tenth of a pound, per yard, per annum; which was determined by taking up three rails, cleaning and weighing them, and then, at the end of twelve months, taking them up again, cleaning and weighing them as before; and this being repeated for two years, the wear was found to be the same.
"We may, therefore, take the wear of the rails to be about onetenth of a pound, per yard, per annum, which, supposing the whole to result from the wear on the upper surface, will be one-eighty-fourth part of an inch; if the top, or wearing part, of the rail were, therefore, an inch in depth, the rail would wear eighty-four years. The whole of the wear above alluded to does not, however take place
upon the top; a part, though, probably, a very small portion, is attributable to exfoliation by the action of the air: supposing, however, that the wear by the action of the wheels amounts to one-tenth of a pound, per yard, per annum; if the top, or bearing part, of the rail be made an inch in depth, it will be sufficient for all the purposes required. Any increased depth and weight, which would not be required for above eighty years, would, at compound interest, at the end of that period, amount to a greater sum than it would be convenient to expend for such a purpose, considering the remote period at which it becomes useful."
Again he says, (page 131)
"Experiments are going on at present, where both kinds of rails, accurately weighed, are laid down, and subjected to the passage of the same quantity of traffic over them; the result of these, so far as they have gone, is in favor of wrought-iron. In the operation of making the cast-iron rails, the surface is partially case-hardened in the casting; this may be seen in all cast-iron rails, extending to a certain depth from the surface. Any experiment, showing the comparative wear, must, therefore, be continued until after the outer hardened surface be worn through; and it is presumed that sufficient time has not yet elapsed to furnish this. We have, therefore, been obliged to reject the data founded on this mode of experimenting, and shall give the result of a different sort of test, more severe, and which, it is trusted, will be deemed sufficiently approximate to justify its presentation to the reader.
Upon the Killingworth railway we had originally cast-iron wheels upon the locomotive engines; about four years ago, we adopted wrought-iron tires. Now, as we have, in this way, the relative wear of cast and wrought iron upon the wheels which run upon the rails; and as the nature of the action will operate nearly alike, whether upon the surface of the rails or of the wheels, we shall, by that means, have a pretty near approximation to the relative wear upon the rails. In this way, we have a considerably more severe test; as, if we take the quantity of traffic, equal to 2000 tons, passing along the railway daily, and suppose the carriages to convey three tons each, with 3-ft. wheels, the relative wear of the wheels and rails is as 53: 1, nearly. "The average wear of the cast-iron wheels was above half an inch in nine months; and, with the wrought-iron tire, the wear of one pair of wheels has been a quarter of an inch in three years, and, with three other engines, one-eighth of an inch in twelve months; making the wear, at least, as five to one in favor of wrought-iron. The actual wear of the rails will not be to the same extent as this, as the engine wheels sometimes slip round, or slide upon the rails, in bad weather. The wear of the wheels of the common carriages will not be so much, for the same reasons; but, although it should be observed, that, from this, we ought not to deduce the actual duration of wroughtiron rails, as, their surfaces being narrower than the wheels, the wear will be, perhaps, more than proportionably greater, yet the relative