Don, Given a train length of a maximum 11 ft, with (do I remember you correctly?) "modern" equipment (50' and longer cars?) it sounds like your trains will consist of a single powered diesel engine followed by ten or eleven cars, including a caboose if used. Unless you are using over-sharp curves on the (hidden) helix, say 30" radius, I seriously doubt that you have much need for reverse super-elevation.
Physics always comes into play, but the factors that create problems for the prototype (1/1 scale) are somewhat different from the factors that cause problems in any but the largest model scales (as in live steamers!) If you are running trains at prototype speeds on larger radius curves (not those big 24" radius American Flyer tracks!!) the use of super-elevation has no positive effect on model train operation, but can in fact be a detriment as I described previously. In the case of a tight radius helix, I would consider using reverse super-elevation, but I don't think you need to bother with it given your train size. I would suggest building the helix with no super-elevation and trying it out to see just where you run into problems. My guess is that you would need a minimum of 20 cars, and probably more like 40 to 50, before there is any likelihood of drawbar pull providing enough lateral thrust to overturn any cars. Build the helix, and run trains up it increasing the length of train until you have a tumble, and you will know how much of a safety margin you are operating with. If you are then not comfortable with your safety margin, you can add shims under the inside rail of increasing thickness. Empirical analysis almost always works, while designing by theory alone often provides factors that are left unaccounted for, providing the need for empirical analysis to find out where theory fell short. After all, all the theory has been based on empirical analysis. Sorry for the long windedness of my response. Hope it helps. Darrell S --- In [email protected], "Don MacDougall" <[EMAIL PROTECTED]> wrote: > > >Darrell raises some good points, > > > Don, > > A better question when dealing with minimum radius curves on a slope > > (as in a helix) is the length of train. The primary factor that > > causes the problem of derailment on helices and other long curves at > > slope is excessive drawbar pull. If your trucks are free-rolling, > the limiting factor is then train length. > > "TRAINS WILL BE A MAX 11ft" > > I can understand the consideration of reverse > > super-elevation, especially on a helix. In most cases the use of > > super-elevation, either normal or reverse, has little effect. > > "SURELY PHYSICS IN THIS CASE AND SCALE MUST HAVE SOME EFFECT ?". > > > One caveat: make sure you have "guardrails" on both inside and > outside of your helix track to catch any wayward cars. > > "SOUNDS LIKE VERY GOOD ADVICE" > > Thanks again, > Don MacDougall > UK. ------------------------------------ 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/
