Figure 2.6. Frog Nomenclature.
is where the running rails are spliced to the frog. The primary classifications of frogs are the spring and rigid
types.
a. Spring frogs provide a smooth, uninterrupted path through the turnout in one direction. The flanges
of wheels passing over the alternate path force the wing rail of the frog open against spring tension. After the
train has passed through the turnout side, the springs force the wing rail back against the running rail, maintaining
the original route for main-line movements. Figure 2.7 shows the operation of this type of frog. The only
justifiable location for spring frogs is in turnouts where traffic is considerably heavier in one direction than in the
other and where it would not be desirable to delay movements through the little-used route. A main-track spring
frog is pictured in figure 2.8, in which the upper arrow points to the wing rail and the lower to the spring
mechanism.
b. Rigid frogs are divided into three groups: bolted-rigid, hard-centered (manganese insert), and
manganese-steel; all three are illustrated in figure 2.9. A rigid frog installed in track is shown in figure 2.10. The
bolted-rigid type is manufactured from standard rail sections cut as required and bolted together. It is standard
military stock and is issued as a unit. Hard-centered frogs have manganese-cast points attached to standard rail
sections. Since the point gets the greatest wear, it is made of extremely hard steel and is replaceable. The
manganese-steel type is of hard steel and cast in one piece. Since manganese-steel and hard-centered frogs have
greater resistance to wear, they are preferable to the bolted-rigid type, especially on main-line tracks and in busy
yards. The latter
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