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 ------------------------------------ Yahoo! Groups Links ------------------------------------ Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/S-Scale/ <*> Your email settings: Individual Email | Traditional <*> To change settings online go to: http://groups.yahoo.com/group/S-Scale/join (Yahoo! ID required) <*> To change settings via email: [email protected] [email protected] <*> To unsubscribe from this group, send an email to: [email protected] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
