Do the math

[THERAILROADNUT]

  rh #5 turnout ---9"st---  90-18%rad  ---4.5"st---  90-18%rad ----9"st---  Lh#5 turnout.    I need to end up with 9"st in the mid for a ez crossing gate between the two turnouts. do i use a combo 15% 18% 22% rad's 9" or 1/4 pic's?. Is this poss? Thank you. PS: ez n/s

[Doneldon]

TRN-

I'm not so sure that I understand your question or your nomenclature but I'll try to help.

First of all, your percent signs should be inch symbols. I have no idea what the "90" digits mean.

Track curvature is measured along two primary dimensions: Sharpness of curvature and how far the curve curves. Real railroads do things a little different - well, a lot different - but for model purposes we need only be concerned with these two factors. Sharpness of curvature is measured by the radius of the curved section in inches. Thus we have 18" or 22" or 30" and so on. But there's another important measurement: How far the curve goes. Using Bachmann EZ Track, 18" radius track curves 30^o, or one-twelfth of the way around a circle (360^o). Twenty-two inch radius track only goes 22.5^o which is why we need 16 pieces of 22" track to make a circle but only 12 pieces of 18" radius track for a full circuit.

You need 180^o of curvature to completely turn your loco or train exactly around. It doesn't matter what radius curves you use, whether you use some straight tracks in your set-up or whether you just mix all of the tracks up and plop them on the basement floor. You'll need more curves to compensate if you stick in a curve going the other way. So if you stick a full 18" curved track going the opposite way you'll need some combination of 30^o coming back; the radius of the compensating curve won't matter. Obviously, some wild mix of curves, straights and reverse curves will give you a mess of track and it may cover a large area, but it will turn your train completely around. Please note that I don't endorse setting your railroad up in this matter and I sure don't advise reverse curves; this was all just to make sure I've made my nomenclature clear.

If I have some idea of what you are trying to do, turn 180^o while leaving in a straight section for a grade crossing, I'll suggest that you simply use the broadest curve you can fit in the space you have rather than using a string of 18" radius curves and straights of different lengths. I haven't plotted your proposed arrangement to see justwhat radius you could use in lieu of the 18" track, but you should be aware that Bachmann makes nickel-silver EZ Track in many radii, including 15", 18", 22", 26", 28", 33.25" and 35.5". Each of these turns a different number of degrees in order to be able to make a complete 360^o circle with only full curves (no piecing with half curves or what have you). You can easily determine how many pieces of track are required for a full circle by dividing 360^o by the number of degrees a curve curves. Thus, a 30^o 18" radius circle will need 360^o/30^o = 12 pieces. And you can find the number of degrees a curve curves by dividing 360^o by the number of track pieces needed for a full circle, e.g., 360^o/16 = 22.5^o for 22" curved sections. It's easier, of course, to just access this information in the product information section of this web site.

To summarize, lose the part curves and straights and just go with the broadest curve you can fit into your layout, with a nine-inch straight section where ever you want that crossing. It doesn't have to be in the middle of your curve unless you want it there.
                                                                                                                                             -- D