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I'm planning an addition to my 4 X 8 HO layout. To go from my layout now to the addition is going to require a double curved turnout. I've been looking at the Peco turnouts and to say the least I'm confused.
The curve I will be using is 22 1/2" R. I'm not sure which diameter Peco turnout to use for this applacation. Also I'm drawing a blank on insul frog and electro frog. I am running NCE DCC now.
Thanks for any help I can get, I'm just at a point I'm totally lost trying to figure this out.
I won't be able to answer specifics about peco turnouts, but there are some things others may want cleared up before they can answer your questions.
The red line you have drawn suggests you are looking for a Y turnout, not a double curved turnout. While a y has 2 curves, they arc in opposite directions whereas a double curved turnout has 2 curves that arc in the same direction. One radius being sharper than the other, or one track inside of the other. An actual double curved turnout placed where you have it will result in the outer curve of the turnout pointing about straight down, not out to the left.
Perhaps Peco's y switches or double curved switches have a radius or frog that will fit into a 22.5 inch radius curve. I don't know.
Atlas makes a 22 inch radius switch that has the traditional shape. The diverging (curved) track separates from a tangent (straight) track and is 22 inch radius. It would be a nearly perfect fit for your diagram. On your diagram, the tangent portion may be able to leave the curved mainline at such an angle that will solve the same problem the red line is solving, if the turnout is re-positioned on the curve a bit. That switch is code 83, if you know what that is.
I'm a dc guy, but I think insulfrog is what you want. And, the Atlas switch is dcc friendly already.
A standard N. American turnout has a straight route through the frog and beyond. Only the closure rails and the points are curved. So, while a snap switch and the British/older Peco have curved diverging routes which may work for you, the N. American style has what is called a 'substitution radius', and for a #6 turnout, that would be about 43" radius. Not what you need. As the previous gentleman suggests, you want a double-divergent turnout, or what we call a wye. Peco must make a British style that has two curved diverging routes, and I would guess that would be a #8 or a #9.
Their PCOSL-97 small Y may be what you want. Scroll down this and other sites' pages to find a good price and more information.
I thought about trying a Y instead of a curved turnout but I'm trying not to destroy to much of the layout thats done already. The curve I'll be working off of is between two mountains(canyon like). With the double curve I can make the turn thru an opening and it will go thru almost an S turn to the addition and it will be the return to the mainline from the addition. I'm not a great artist but this is a little better I think below showing what I mean. Also the Y will have a straight section that may not work in the middle of the turn. I'm not sure. And then again I maybe way off on my thinking and need to use a Y. This is why I'm so confused about it. I also added a pic of the area I'm talking about. The track is mainline code 100.
Despite what others have said, I don't think you want a wye. That will automatically create an s-curve that could prove troublesome. Either a straight turnout or double-curved could avoid or minimize the s-curve.
There is no off-the-shelf turnout (curved or not) that will fit exactly into your existing curve. Even the double-curved turnouts are slightly off a pure radius curve, and none comes in precisely 22.5" radius on the inner curve (of which I'm aware).
I think that for this to work you are faced with some rebuilding of the curve, sorry. In the end, it will probably have the effect of slightly sharpening the curve radius to incorporate any turnout unless you can shift to the outside the straight tracks leading into the curve.
It might help others help you to know what PECO system you are using, Code 75, Code 100, or Code 83.
Insulfrog vs. Electrofrog is not a show-stopper, IMHO. With proper gaps and feeders, either works fine with either DC or DCC.
Now that I see what you see, I agree that your best fit will be a British style #4/5 with a curved diverging route left. It would be unusual for a main line to exit via the through route of a turnout, but ya gotta do what ya gotta do. Do that myself in three places.
A normal straight/curved turnout, Peco medium left, should do the best job of sparing the rock cut on the right. It won't be the same curve radius going left on the main, but it will be close enough. You will surely have to shift some roadbed/track, but it won't be a showstopper.
