\fdO'^ - Old Forge Coal Mines

RAILROAD LOCATION. 273
in which;!' = 28° 40', the given angle of the second curve;
A' = 1,910.08 ft, the radius of a Z° curve; r = 71G.78ft., the
radius of an 8° curve, and Z> = 25.4 ft., the distance between
the given tangents. Substituting these values in the above
formula, we have
''''^^
(l,910.08-716.78)X.87743+a5.4_-.89872-cos26 o^o^.^^^orooo' 00.
1,910.08-716.78
The given angle of the second curve is 28° 40', and the
required angle is 26° 00'. The difference, 2° 40', we must
deduct from the second curve and add to the first, i. e., we
must advance the P. C. C. The number of feet which we
advance the P. C. C. we determine by dividing the angle
2° 40' by 8, the degree of the first curve; the quotient gives
the distance in stations. Reducing 2° 40' to the decimal of
a degree, we have 2. 6667°. —5-— = . 3333 station = 33. 33 ft.
8
(793) This question is also under Problem II, Case 2.
(See Art. 1424.) Here we increase the angle of the second
curve, and, consequently, diminish the cos, and D the distance
between the tangents is negative. We use formula
100. cos Y = -^^
' -^ K — r
'n , m
which x = 30 15 . A
=
1,432.69 ft., r = 637.27 ft., and Z) = 33 ft. Substituting
these values in the given formula, we have
^^^>'^
(1,432. 69-637.27) X. 80644-33 ,^.^_ , .„ ^n'
The given angle
1,432.69-637.27
= -C495cos40 06.
of the second curve is 36° 15' and the*
required angle 40° 06'. The difference, viz., 3° 51', we add
to the second curve and deduct from the first. We must,
therefore, place the P. C. C. back of the given P. C. C, and
this distance we find by dividing the angle 3° 51' by 9, the
degree of the first curve, deducing 3° 51' to decimal form,
we have 3. 85°. ^
= .
4278 station = 42. 78 ft.
(794) This question comes under Problem III, Art.
1425. The radius of a 7° curve is 819.02 ft. The radius