> Posted by: "John Degnan" [EMAIL PROTECTED] scaler164
> Date: Mon Jan 14, 2008 2:52 pm ((PST))
>
> Based on this... what should the degrees of graduation be in
> tightening of curves; 2 degrees per some-odd distance or some larger
> degree per whatever distance? Is all of this covered in Armstrong's
> book?
John Armstrong favors the "bent stick" method, which he describes as a
fair, practical approximation of the mathematical "cubic spiral" used
by railroads.
His book covers the technique for curves of various sizes, including
24, 30, 32, 42 and 54 inches. For example, the transition from
straight track to a 42-inch radius curve would be 25 inches long and
the center of the curve would be offset 5/8-inch. See the book for
details. (It's also discussed in the NMRA Data Sheets, and the
technique must be described on the Internet somewhere.)
"Degrees of curvature" has no real application to model railroading.
It refers to the angle formed at the center of a curve between two
points on the curve. It also refers to the procedure used by railroad
surveyors to lay out a curve. Railroads favor small degrees of
curvature, which make for impossibly large radius curves for model
railroads.
I didn't use transition curves on my small layout, because I settled
on a 44-inch minimum radius and didn't figure they would be necessary
for operation. However, I do see equipment lurch slightly when
entering or leaving a curve, so some kind of transition is desirable,
if only for looks.
--
Bill Roberts
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