switch numbers Switch/Turnout
Numbers From S-Trains submitted by SMITTY
(I added the graphics,PAUL)
There is a relationship between the "number" of a switch
and it's radius, although correlating the two gets pretty
complicated.
Basically, the smaller the number, ie, a #5 or a # 6,
the smaller
the radius that comes off the switch. Good for yards or
industrial
spurs, but not high speed. If you were to run your Broadway
Ltd. at
timtable speeds you'd want a # 21 or therebouts when cutting
over
from one mainline to another.
The number of a switch is derived from the tangent of
angle formed
by the frog of the switch. Use a left hand turnout as
an
illustration. Take your measuring scale and place it perpendicular
to the left rail of the "main route" track with the "zero"
end of the
scale on the gauge side of the rail. Slide it along the
straight
rail, past the frog until the 1/4" mark rests on the gauge-side
edge
of the outside-of-curve rail of the diverging route.
Stop here and
note the place where the "zero" end of your scale is on
the straight
rail. Now measure back, along the straight rail to the
"point" of the
frog, that is, where the gauge lines of the staight rail
( on the
left side ) and the outside-of-curve rail would intersect.
It'll be
about where the "x"-shaped groove in the frog is, where
the flanges
of the wheels go. If you measured 1 1/2", which works
out to be six
1/4" increments, your switch would be a # 6. If you had
measured 2",
that would be eight 1/4" increments and your turnout would
be a # 8 .
If you recall your trig, the tangent of an angle was the
"opposite"
side of the triangle over the "adjacent". In this case
the "opposite" side was the 1/4" measurement, and the
"adjacent" side
was the 1 1/2" or 2" measurement. In reality, the relationship
is
actually the arc-tangent ( 1 / tangent ) but that's getting
picky !
