Is that a chord from a piano or french horn?
John Armstrong
----- Original Message -----
From: David Heine
To: [email protected]
Sent: Saturday, July 07, 2012 8:50 PM
Subject: RE: {S-Scale List} Re: Basic Geometry
Jim is correct, the degrees of curvature applies to a 100' chord. If you
work through the math, for S scale it works out to:
R = 75/(8*sin (A/2))
Where R = radius in inches for S scale; A = degrees of curvature for the
prototype
Since I know more about narrow gauge: a typical minimum design curvature for
an early narrow gauge railroad was 24 degrees. The sharpest curve on the
D&RGW narrow gauge was a 25 deg 30" curve between Marshall Pass and
Gunnison. This corresponds to a 42" radius in S. However, the Uintah, also
in Colorado, had a 66 deg curve over Baxter Pass, and this was after it was
straightened when they purchased their articulated locomotives. Previously
they had used Shays for the portion of the mainline over the pass. This
corresponds to 17" in S, which most modelers would consider very sharp. Of
course, different equipment was operated on these two lines.
Dave Heine
Easton, PA
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of
raisinone
Sent: Saturday, July 07, 2012 3:16 PM
To: [email protected]
Subject: {S-Scale List} Re: Basic Geometry
--- In [email protected], "David Engle" <rirocket@...> wrote:
>
> Can someone please recommend a cheap calculator or app that will do the
radius of a curve when the arc and chord lengths are measured. DJE
>
Don Thompson turned me on to this web site so many years ago he's probably
forgotten. It might have information for you though I cannot guarantee all
the links still work.
http://www.urbaneagle.com/data/index.html
It is my understanding that prototype curves are measured by degree of
central angle subtended by a 100' chord (From Paul Mallery's Trackwork
Handbook). It is also my understanding that 10 - 12 degrees is extremely
tight for prototype. That converts to a radius of ~7.5 to 9 feet(!) in S
Scale. Or conversely, an S Scale 40" radius curve would be about 27 degrees
on the prototype.
Not sure if that helps, but there's a ton of other info on the site you
might find useful...
Jim Kindraka
Plymouth, WI
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