# Turnouts and Radius?



## Rmay (Nov 19, 2009)

What are your recommendations for turnouts going into a 36" radius curve,as well a turnout going into a 48" radius?The turnout from the switch would be part of the mainline,not turning out going into a siding.would it be a #6 turnout going into a 36" radius mainline curve,as well,a #8 turnout for going into a 48" radius mainline curve.I hope I explained this ok,Thanks again,Randy


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## Steve Stockham (Jan 2, 2008)

If I understand you correctly, I believe that the Wide Radius (#4) turnout matches up with the 48" radius curve while the #6 turnout matches up with the 60" radius curve. Where would you get a #8 turnout?


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## RimfireJim (Mar 25, 2009)

Randy, 
A prototypical switch is made up of three sections: straight switch points, curved closure rails, and straight rails through the frog. A model switch may be made that way, or with all curved rails for the diverging route. Is your goal to ensure that the curvature in the switch is no less than that of the curve it is leading into? If so, it will be necessary to know if you are using a prototypical switch or one of the all-curved types. And, if prototypical, what scale are you working in?


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## Rmay (Nov 19, 2009)

Steve: "SwitchCrafters" makes #4 - #10 
as well as curved turnouts. 

RimfireJim: the one I'm asking for would be a prototypical straight turnout, 
the turnout itself continues my mainline onto a curve of 48 degrees/ 96", 

so it seems a #4 would work, but a #6 could be a smoother transitional arc, 
Randy


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## Greg Elmassian (Jan 3, 2008)

The Aristo WR switch is 5' radius, and the diverging route and the rails past the frog continue the curve. 

The #6 is a true turnout, i.e. not curved to match a piece of curve track, it's closer to a 7-10 foot radius 

I would use the "broadest" switch you can fit, unless you are trying to match a continuous curve, like the diverging leg of the turnout is in the MIDDLE of a curve. At the beginning or ending, you can have a broader "curve" from a turnout, it does not NEED to match. 

Regards, Greg


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## RimfireJim (Mar 25, 2009)

Posted By Rmay on 30 Nov 2009 03:42 PM 
Steve: "SwitchCrafters" makes #4 - #10 
as well as curved turnouts. 

RimfireJim: the one I'm asking for would be a prototypical straight turnout, 
the turnout itself continues my mainline onto a curve of 48 degrees/ 96", 

so it seems a #4 would work, but a #6 could be a smoother transitional arc, 
Randy 
I'm thinking you mean 48" radius/96" diameter there, not degrees. Prototype rail curvature is measured in degrees - the angle subtended by a 100' chord - but your numbers would work out to a very odd scale.

To know what the closure rail radius is of a numbered switch, you actually have to know what scale it is built to, because scale affects length which in turn affects radius. An HO scale (1:87) #4 switch has a much tighter radius than a 1:32 scale switch. The only constant there is the frog angle. Switchcrafters doesn't state what scale they are using, only "narrow gauge" and "standard gauge". One might assume that means 1:20.3 and 1:32, but in this hobby it could also be 1:22.5 and 1:29 or anything approximately close to those. Or they may be exactly the same switch rails with just different tie spacing. Your best bet, if you want to know exactly, is to ask them directly what radius their switches use.


Using a cool turnout calculator by David Honner I found on line, I get the following numbers for closure rail centerline radius:

Fn3 (1:20.3 narrow gauge on #1 gauge track)

#4 - 37.8"

#6 - 98.6"

#8 - 194.6"


Un-named 1:29 (common usage on #1 gauge track)

#4 - 43.4"
#6 - 110.4"

#8 - 219.3"

That's assuming I did it right - I ran through the calculator kind of fast. The bottom line is, always use as big of number as you can fit.


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