| Distance centre to centre of tie. | Distance clear. | Weight of rail. |
|---|---|---|
| 1½ feet, | 1 feet, | 60 lbs. per yard. |
| 2 feet, | 1½ feet, | 60 lbs. per yard. |
| 2¼ feet, | 1¾ feet, | 60 lbs. per yard. |
| 2½ feet, | 2 feet, | 60 lbs. per yard. |
| 2¾ feet, | 2¼ feet, | 65 lbs. per yard. |
| 3 feet, | 2½ feet, | 65 lbs. per yard. |
| 3¼ feet, | 2¾ feet, | 70 lbs. per yard. |
| 3½ feet, | 3 feet, | 75 lbs. per yard. |
The amount of inclination or bevel to be given to the cross section of the rail, depends directly upon the cone of the wheel, and indirectly upon the gauge of the track. (See Chapter XIV. part 2.) The radius of curvature being averaged at 2°, or 2,865 feet,
| Feet or | Inches. | |
|---|---|---|
| For the 4′ 8½″ gauge it should be | .0017 | .020 |
| For the 5′ gauge, | .0017 | .020 |
| For the 5½′ gauge, | .0019 | .022 |
| For the 6′ gauge, | .0021 | .025 |
in the width of the rail, or two and one half inches.
The above dimensions embrace all of the best results of experiment and experience, and at the same time satisfy the conditions demanded by the mechanical and physical nature of the material—iron.
CHAIRS AND JOINTS.
287. The chairs most common at present are made of a wrought iron plate, with two lips, either cut and punched up, or forged up, to hold the lower web of the rail. Such chairs weigh from six to ten pounds each, and are less liable to break than the common form of cast-iron chairs. It is probable that a cast-iron chair may be made, however, with properly shaped lips, and so hollowed out as to be at once strong and light. (See Clarke’s R. R. Machinery, “Permanent Way.”)
Of late the chair of Mr. David L. Davis, of Dedham, Mass., has attracted considerable attention, and bids fair to be the means of obtaining a better rail surface than has heretofore been possible. This gentleman has been for twenty years Road-master of the Boston and Providence Railroad, and has had ample opportunity for considering the subject of track laying in every respect. The rail bears upon a cap of wrought iron, which rests upon a piece of rubber, lying in the chair. The testimony of the leading managers of the New England Railroads bears witness of the excellence of the arrangement.
The practice of notching each end of the rail causes the expansion to be exerted directly against the fastenings, which should not be the case. Some point should be fixed longitudinally, to resist the end shocks from the wheel. This point should be either the centre or one end of the rail. End chairs may hold the rail laterally, and vertically, but not longitudinally.
The weakest part of the track is that, where, to resist the concussions of the wheels it should be strongest, namely, at the joint: here we lose the strength of the rail and depend entirely upon the tie. The flattened ends of rails which have been laid for a few years show the bad effect of the common joint. The complete remedy for this is, so splicing the rail that it is as strong at the joint as elsewhere. The method termed “fishing,” is not much more expensive than the ordinary method of jointing, it is perfectly effectual, and has had the test of long and successful use. It consists in bolting a plate two and one half feet long, two and one half or three inches wide, and from one third to one half inch thick, to the ends of both rails making the joint; one plate being placed on each side. The plates are convexed a little from the rail as in fig. 138, so that being sprung by screwing on the nuts, the latter shall not work loose by the vibration of the rail.