\fdO'^ - Old Forge Coal Mines

TRACK WORK. 303
( 1 003) This example comes under Case I of Art. 1 693.
The sum of the tangent deflections of the two curves for
chords of 100 ft. is equal to the tangent deflection of a 1G°
30' curve for a chord of 100 ft. This deflection, we find
from the table of Tangent and Chord Deflections, is 14.35
ft. Calling the required frog distance x, we have, from Art.
1692, the following proportion:
whence,
x' =
14.35 : 4.75:: 100' : x';
, , 100^X4.75 47,500 „ .^ .
and X =57.5 ft. Ans.
^^-^ — = -^jj^ = 3,310,
As the central angle subtended by
a 100-ft. chord is 10°
30', the angle subtended by a chord of 1 ft. is
'
=9.9',
and for a chord of 57.5 ft. the central angle is 9.9' X 57.5 =
569.25' = 9° 29^' the required frog angle.
(1004) This example comes under Case II of Art.
1693, in which the curves deflect in the same direction.
As the main track curve is 4° and the turnout curve 12°,
the rate of their deflection from each other is equal to the
deflection of a 12° — 4°, or of an 8° curve from a straight
line. From the table of Tangent and Chord Deflections,
we find the tangent deflection of an 8° curve for a chord of
100 ft. is 6.98 ft. Now, the distance between the gauge
lines at the head-block is fixed at 5 in. = .42 ft., and calling
the required head-block distance x, we have the proportion
whence,
6.98 : 0.42:: 100' :x';
.r" = 601.7, and
head-block distance x = 24.5 ft. Ans.
( 1 005) Multiply the spread of the heel by
the number of
the frog; the product will be the distance from the heel to
the theoretical point of frog.
(1006)
See Art. 1694.
(1007) 60 X 12 = 720 in. 720 -^ 15 = 48. Ans.