b. Classification. Turnouts may be classified according to their direction and sharpness. The direction
of a turnout is determined by viewing it from the main track as you face the switch points, that is, the movable
rails. If they run to the left, the turnout is left handed; if to the right, right handed.
The sharpness of a turnout is determined by the acuteness of the frog angle, that is, the angle formed by
the rails extending from the heel to the actual point of the frog and by the length of the switch rails. Not only is a
frog designated by its angle but, more commonly, by its number. The larger the number of the frog, the less
sharp the angle of the turnout. The number is approximately the same as the length of the heel given in standard
tables of turnout data. For example, the heel of a No. 8 frog is 7 feet 11 inches long and that of a No. 20 frog is
19 feet 10 inches. Common frogs are Nos. 8, 10, 15, and 20. The standard military one is the No. 8, discussed in
paragraph 2.5.
2.4.
SWITCHES
Through the years, switches have been designed in several ways; however, the two designs that have
endured are stub and split switches.
a. Stub switches, once common in the United States, are seldom used here any more. Most states have
outlawed them on main lines; however, they may be found in some oversea areas. More information on their use
there is given in section V. Though simple and economical to construct and operate, stub switches are difficult to
maintain and are quite unsafe; many derailments have been caused by them. They depend upon perfect alinement
of the rails for proper operation. Their great advantages consist of economy and adaptability to light, slow
traffic.
Study the layout of the stub switch turnout shown in figure 2.2 as you read the remainder of the
subparagraph. Up to point A, the rails are spiked to the ties but from there on the rails are not spiked. Instead
they are fastened to each other by tie rods that keep them at the correct gage. At B, the rails are held in place by a
connecting bar fastened to the switch stand. The connecting bar is indicated by the shaded portion between B
and C. Both main-line rails in the stub switch move.
b. Split or point switches have replaced the stub design on modern United States lines, because they
have proven safer and more
31
Previous Page
