We have
D = 2(4.708 – .417) × 240/5 + 72/(6 + 3)
240/5 + 72/(6 + 3)
or, D = 8.582 × 48 × 8
48 + 8 = 58.85 feet.
In laying the rails, the distance from the point to the end of the frog (towards the switch) is to be taken from the above.
Table showing the distance between the frog and switch, gauge 4′ 8½″, movement of switch-rail five inches. Frog six inches across head, and three inches at mouth. Main track being straight.
| Length of frog. | LENGTH OF SWITCH RAIL. | |||||
|---|---|---|---|---|---|---|
| 12 | 14 | 16 | 18 | 20 | 22 | |
| 3 | 29.1 | 29.7 | 30.1 | 30.4 | 30.7 | 30.9 |
| 3½ | 33.3 | 34.0 | 34.5 | 35.0 | 35.3 | 35.6 |
| 4 | 37.3 | 38.2 | 38.8 | 39.4 | 39.8 | 40.2 |
| 4½ | 41.1 | 42.2 | 43.0 | 43.7 | 44.3 | 44.7 |
| 5 | 44.8 | 46.1 | 47.1 | 47.9 | 48.5 | 49.1 |
| 5½ | 48.3 | 49.8 | 51.0 | 51.9 | 52.7 | 53.2 |
| 6 | 51.7 | 53.4 | 54.8 | 55.9 | 56.8 | 57.6 |
| 6½ | 55.0 | 56.9 | 58.5 | 59.8 | 60.8 | 61.7 |
| 7 | 58.1 | 60.3 | 62.1 | 63.4 | 64.7 | 65.7 |
| 7½ | 61.2 | 63.6 | 65.6 | 67.2 | 68.5 | 69.6 |
292. When the switch rail is short, the angle between the main line and the switch rail, when switched, is considerable; and causes quite a shock to the passing engine. The switch shown in fig. 145 remedies the evil, makes the machinery compact, and the calculation simple. The tangent point of the turnout curve is at n n (the usual heel). In place of adjusting the single to the double line of rails, the double is adjusted to the single line. The data given are the gauge and radius of curve; and as before, the elements required the frog angle and distance from switch to frog point.
Fig. 145.
Now