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The elements of railroad engineering (Volume 2) online

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the ratio of its length to its breadth, i. e., the quotient of
its length divided by its breadth.

Thus, in Fig. 523, if the length a' /, from point to heel of
frog is 5 feet, or 60 inches, and the breadth h of the heel is
15 inches, the number of the frog is the quotient of GO -=- 15 =
4. Theoretically, the length of the frog is the .distance
from a to the middle point of a line drawn from k to /;
practically, we take as the length the distance from a to /.
As it is often difficult to determine the exact point a of the
frog, a more accurate method of determining the frog num-
ber is to measure the entire length d I of the frog from mouth
to heel, and divide this length by the sum of the mouth ^vidtJl
b and the heel width h. The quotient will be the exact number
of the frog.

For example, if in Fig. 523, the total length d I of the
frog is 7 feet 4 inches, or 88 inches, and the width //is 15
inches, and the width b of the mouth is 7 inches, then the
frog number is 88 -^ (15 -f- 7) = 4. Frogs are known by
their numbers. That in Fig. 523 is a No. 4 frog.

1680. The Frog Angle. The frog angle is the

angle formed by the gauge lines of the rails, which form its
tongue. Thus, in Fig. 523, the frog angle is the angle la' k.
The amount of the angle may be found as follows: The
tongue and heel of the frog form an isosceles triangle (see
Fig. 524). By drawing a line from the point a of the frog

to the middle point b of the heel c d, we form a right-angled
triangle, right-angled at b. The perpendicular line a b,


bisects the angle #, and, by rule 5, Art. 754, we have tan
^ a =: j. The dimensions of the frog point given in Fig.

524 are not the same as those given in Fig. 523, but their
relative proportions are the same, viz., the length is four
times the breadth. The length a b 4, and the width
c d =. 1 ; hence, b c . Substituting these values, we have

tan | a = | = | = 0.125. Whence, a = 7 7f , and a =

14 15'; that is, the angle of a No. 4 frog is 14 15'.

Frog numbers run from 4 to 12, including half numbers,
the spread of the frog increasing as the number decreases.

1 68 1 . Classification and Description of Frogs.

Frogs, as manufactured to-day, are of two classes, viz., stiff
frogs and spring-rail frogs. Each has advantages peculiar
to itself, which specially adapt it to certain situations.
Stiff frogs contain much less material and require less
shop work than spring frogs. For a given angle a stiff
frog requires less space, and hence is better adapted to yard
work than spring-rail frogs. They are more simply con-
structed than spring frogs, and can be made at any well-
equipped machine shop.

Spring-rail frogs, because of their furnishing an unbroken
surface to the wheel treads, are particularly adapted to the
heavy traffic of a trunk line.

Figs. 525 and 526 represent the best types of stiff frogs.
The frog shown in Fig. 525 is called a plate frog. The
rails composing the frog are fastened to a plate of wrought
iron or steel a c d b by means of rivets through the rail
flanges, as shown in the figure. Square holes e, f are



punched in the plate to receive the railroad spikes, which
are driven into the cross-ties supporting the frog, holding it
firmly in place. Plate frogs are perfectly rigid, and by many
railroad men are considered inferior to the keyed frog,
shown in Fig. 526, which is somewhat flexible and better

suited to yard work where the curves are sharp and the frog
angles correspondingly large.

In this frog, the pieces of rails a and b, forming the point,
are dovetailed together and secured by heavy rivets. To
retain the full strength and durability of the steel, all the
parts are fitted without being heated, excepting the wings,
which are bent at a very low heat. Hence, the strength of
the rails is in no respect diminished, and the method of
securing the parts together has advantages over bolts or
rivets passing through the webs or flanges of the rails, as
there is nothing which can come in contact with the wheel
flanges. From its peculiar construction, it has the same
elasticity as the rails in the track, which makes it an easy
riding- frog, more durable than a rigid frog, and less liable
to injury from uneven ballasting. It presents little obstruc-
tion to tamping, and, when fastened into the track with the
usual angle splices, it is firm, stable, and free from any
tendency to jump or move.

The parts are bound together by heavy wrought-iron
clamps c and d, shown in the cross-sections A and />, A
being a cross-section through the first clamp and B one


through the second clamp. These clamps are tightened by
means of beveled split keys, or wedges, e and /", the ends of
the clamps being bent over a form to an exact angle, at one
end to fit the brace blocks k and k' on the outside of the
rail, and at the other end to fit the beveled keys, which are
driven into the spaces between the end of the clamp and the
smaller brace blocks /, /'. The keys lie on the flange of the
rail, which prevents them from dropping down in case they
loosen. The flange way between the frog point and the wing
rails is maintained by iron throat-pieces g, //, g' t and //',
which fit the rails perfectly, and, extending beyond the
point, thoroughly brace and stay it against lateral stresses.
After tlie keys are driven to the extent necessary to bind
the parts solidly together, the split ends are spread to
prevent the keys from working out.

The throat-pieces, as well as the brace blocks, are effect-
ually prevented from sliding out of their positions. The
clamps are firmly secured to the flanges of the rails, and the
only movable pieces in the frog are the keys which, being
thicker on their lower edge (owing to being beveled un-
equally), together with the angles of the clamps, prevent
the keys from working upwards. Trackmen, when inspect-
ing track, should always examine the frogs, and any key
loosened by the wearing of the parts should be tightly driven,
and the split end spread open. Unless a key is loose it
should never be hammered.

A standard type of a spring-rail frog of keyed pattern
is shown in Fig. 527. For main line tracks, and especially
for those sections where the heavy traffic moves principally
in one direction, the spring-rail frog is recommended. It
gives to the main line the smoothness of an unbroken track;
it is simple in its construction, thoroughly substantial, and is
placed in position with the least amount of labor.

As shown in the figure, the fixed parts of the patent keyed
spring frog are bound together by two heavy clamps a and "#,
shown in the details A and />, which are sections through
the clamps at C D and E F. The parts within the clamps
are secured by split keys or wedges c and d. The frog point



G is made of two
pieces of steel rail
fitted and dovetailed
together by machin-
ery, without being
heated, and securely
riveted together. The
flange way between
the point and wing
rails is maintained by
closely fitting iron
throat-pieces e and f
(shown in the detail
sections A and B],
which are prevented
from slipping by rivets
and pins through the
rails. The clamps
have side notches g
and g' at one end
(shown in detail at Z),
which engage with
notches in the flange
at the frog point, and
prevent the clamps
from slipping down,
even if loose. The
other end of the clamp
is bent over a form to
an exact angle to fit
the beveled split key,
which is driven into
the space between the
clamp and the block,
which is fitted and se-
cured to the side wing
rail. When the key is
driven, the parts of

Online LibraryInternational Correspondence SchoolsThe elements of railroad engineering (Volume 2) → online text (page 35 of 35)