Oh Oh, guess I did it the hard way; a couple years ago I bought a 6-foot long piece of .250 rail just for this purpose. How viable would it be to make sure the each end is spiked down straight for a short distance to make sure the spiral does not spill to the outside of theoretical centerline in that area. There is an error factor that is half the width of the rail base, but I hope it is not enough to be concerned about. DJE-KCMO
----- Original Message ----- From: raisinone To: [email protected] Sent: Tuesday, January 15, 2008 12:42 PM Subject: {S-Scale List} Re: Curve radii --- In [email protected], Bill Roberts <[EMAIL PROTECTED]> wrote: > > > 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 > Spiral easements are also covered in Paul Mallory's trackwork handbook, a key reference I have used. In the apppendix he provides a simple easement template to create spiral easements. I have seen easements allow a long wheel base locomotive to negotiate curves a couple inches tighter in radius than the 48" minimum of the locomotive's wheel base. It may be that "lurch" at the curves entry is important, even at a wider radius... FYI.. The 12" to the foot gauge railroad's generally try not to have curvatures higher than 10 degrees and a 14 degree curve on a mainline would be considred extremely tight, probably about the max. A 10 degree curve is a little better than 102" in radius in S scale. A very generous but more "S scale doable" curve of 54" radius relates to 20 degrees of curvature on the prototype... Some things can be "scaled", others... probably not. Jim K. [Non-text portions of this message have been removed] 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: mailto:[EMAIL PROTECTED] mailto:[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/
