<BLOCKQUOTE>quote:</font><HR>Originally posted by tigerman: Can someone give me advice or direct me to a good source on laying out min. radius curves. <HR></BLOCKQUOTE> Welcome.. What scale are you working in? and also what locos and rolling stock you intend on running? eg Short diesels, or long steam, they all make a difference! ------------------ RR: K, C, & Bird Butt Railroad - SP, NS, and ROCK admirer. Its a coal mining region of a place far far away, that runs, SP, NS, and some CSX.. Also some Custom RARE Bird RR sd40-2's coming! Era: Time stands still round these parts, and we have everything from Steam, to Diesels of today.
The web is funny tonite, hope you get this. Real railroads can not 'layout' a radius like we do on a paper or board because of a mountain or lake in the way. Curves are actually a parabola, not a true radius. If an engine, which is top heavy, going fairly fast on a straight track suddenly ran onto a curved section of radiused track, momentum would want to keep the engine going straight on, while the track would carry the wheels sideways making the engine roll over. To prevent this, surveyors have formulas they use for 'laying out' curves, that are generally spoken of as the "degree of curvature". Simply it means that from a straight track's end (the point of tangency), measure 100 feet straight ahead, drive a stake. Swing the transit (right or left) the number of degrees of the curve at that point (maybe 2 degrees). Measure at that degree, 100 feet and drive a stake. This is the begining of the "Easement" of a curve. It is a gently increasing curve to prevent the engine turning over. At the mid point of a curve is the greatest number of degrees (maybe 20 degrees), after that the number of degrees go down until the track again becomes straight, which is the other point of tangency. In HO a 20 degree radius is 44". For Hobby rails, like say HO, use a section maybe a foot long of 60" radius, a foot of 48" radius,and a two foot long section of 36" radius then reverse the sections until straight again, and your track curve will look pretty good, and your engines can negotiate it at a fairly high speed. (You may have to go with 6" sections and go down to an 18" radius, its OK) Real railroads also "Bank" the curves like on a highway. It is called "Super Elevation". The outside rail is 'elevated above the inside rail gradually from flat level at point of tangency, to maximum elevation at the mid point between points of tangency, then gradually returns to flat level at the next point of tangency. Anything too abrupt will derail the train. It can also make your wheels lose electrical contact. The shorter the curve, the higher the outside rail. Model trains will turn unrealistically tight curves and get away with it, like a Lionel toy. Most modelers prefer to provide as much realism as they have room for, so you can figure all HO trains will go around an 18" radius curve slowly. All HO equipment will go through a #6 switch (turnout) OK. Some smaller engines will go thru #4 turnouts. Long passenger cars will have trouble on #4 turnouts. Degrees: A 20 degree curve is, straight ahead 100', swing the transit 20 degrees (left or right) and go 100', put a stake, nail, mark an X. At this point again swing the transit 20 degrees same way, measure 100', drive a stake, repeat process. If you continue it will be a true radius. The Union Pacific Big Boy was designed to go around a 20 degree curve, so would also go around a 16 degree curve, but not go around a 30 degree curve. See? The actual surveyor's formula for a real eased curve is terriblely complicated, so I wont bother to get the book out. You wont need it. Now you have the basics. Whatever scale you use, the curve's "radius" will probably be determined by the space you have to put the whole layout in. Just use comon sense and try to provide some easement on both ends of each curve, and a little "bank" (Like one or two thicknesses of a credit card) only on the outside rail at the mid point of your curve. Fill in gradually up to and away from, so there is no 'bump'. School is always open on the Trainboard, everybody will help, so if you need more info, just ask and someone will give you an answer. Have fun ------------------ Watash [This message has been edited by watash (edited 31 October 2000).]
Thanks for the suggestions. I meant to say "laying out radius..." but you guys got it. The layout will accomodate ho 1960s, 70s short locos but will also include a passenger line. I like the common sense approach, but also want to get some sense of the width that will be needed in building the benchwork. I am planning 6' islands at this point. Any more advice?
Well, it isn't necessary to re-invent the wheel, so to speak. The NMRA has a curvature Recommended Practice RP-11 that gives you an idea of recommended curves in relation to both the locos and cars that you are running and the prototype's curvature in degrees. You can find it at http://www.nmra.org/standards/ Just take the Recommended Practices link and look for RP-11. Roger Roger Hensley - rhensley@anderson.cioe.com == http://www.nmra.org/standards == == NMRA Standards and Recommended Practices ==
Well, I'd say that covers all the bases! I super-elevate my N-Scale curves too, it helps ease the stresses and LOOKS COOL! ------------------ Brent Tidaback, Member #234 BNSF Railfan-to-the Max and a N-Scaler to boot! "Ship it on the Route of The Roadrunners!" The Aransas Odessa & Western, a division of the BNSF
<BLOCKQUOTE>quote:</font><HR>Originally posted by Maxwell Plant: I super-elevate my N-Scale curves too, it helps ease the stresses and LOOKS COOL! <HR></BLOCKQUOTE> I agree 100%, superelevation of curves makes a huge difference, especially when a double stack is on the curve ------------------ Alan The perfect combination - BNSF and N Scale! www.ac-models.com Andersley Western Railroad Alan's American Gallery [This message has been edited by Alan (edited 31 October 2000).]
To help you along a little further, check out the archives of Model Railroader they published an easment template in HO. We use it on our RR. I don't have a scanner otherwise I would scan it in and send it to you. ------------------ When in doubt, empty your magazine. Member #33
