Fig. 146.
Example.—Let the radius of outer rail be five hundred feet, and the gauge five feet. We have, then, the distance
(A.) D = √5002 – 4952 = 72 feet, very nearly.
Also, Sin E C D = Sin 90 log D
log R,
(B.) or Sin 90 log 72
log 500 = 8° 17′,
and the length of switch
(C.) √5002 – 499.652 = 18¾ feet nearly.
Five hundred feet is, therefore, about the longest radius for which such switches should be used.