# Need help determining inside loop diameter size



## sldozier (Apr 5, 2009)

I'm starting to lay track (Aristo) on a raised platform, as I'm planning on live steam in the future and my back and knees can't take the constant bending required to maintain a ground level railroad running live steam!

Anyway, I have a 10ft diameter outside loop (max dia my layout can accomodate in my initial buildout) and I'm considering a single or "X" crossover to an inside loop! I've already purchased switches (Aristo Wide Radius). 
Configured a single crossover (back to back switches) (track spacing is approx 7" center to center) but can't tell if that spacing dictates a 9 foot or 8 foot inside loop diameter. I know it's one or the other, but I don't want to guess wrong and end up having to purchase additional track, I might not need. Can anyone whose done this configuration before, or anyone who has the magic formula (besides guestimating) lend a hand please? I also placed a 1 foot section of straight track between the switches, which widens the track spacing to approx 11' center to center, and I think I like that spacing alot better, but again I'm trying to determine what that track spacing would dictate as far as an inside loop is concern. And ofcourse an "X" crossover will add yet another dimension to track spacing I'm sure, that I'll need to figure out the what diameter that subsequent inside loop will need to be. Any help would be highly appreciated!


Back to persuing through the many informative posts here. WOW 



Stefan


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## Totalwrecker (Feb 26, 2009)

I don't think anybody can hand you that formula, there are too many variables. 
You should be able to figure out two things; 
1 how far away from the present track will the cross over be, you've done that. 
2. Experiment with your equipement check for clearances, See where your overhang is greatest. I'd draw some centerlines of known track radii and set cars along it and see how passing equip looks. 

All this hinges on the size of equip you run, but it looks like you have answered your question with the 11" spacing... 8' diameter unless you want a kidney shaped inner loop, but that could induce odd reverse curves and switches.... restricted speed zones!


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## pimanjc (Jan 2, 2008)

I used a 30 degree crossover with the WR [ 10ft ] switches. The frog angle on the WR switch is 15 degrees. If you use the #6 switch [ 9.5 degree frog angle ] then the 19 degree crossover is needed. 


In the case of the WR switches, they curve away past the frog, thereby increasing the effective angle of the frog. That is why the "straights" between the switches are slightly bowed outward. Belly bending should work after screws holding track to ties are removed. After bending to correct contour, then cut the track to proper length as physically marked while in place. There will also be a slight angle to the inside of the outgoing rails. Since I was coming off curves on both ends, that was of no consequence for me. 
If you have room, the #6s/19Deg. combination is much easier to work with, but takes significantly more space. 

Using the WR switches, I have a 9.5in center-to-center track spacing. The eastern end of the crossover goes into a double curve with an 8ft diameter curve on the inside. Either 10ft or 12ft diameter curve can be used on the outside [I bent mine with a Train-Li]. Maintain a center-to-center minimum distance of 6 inches. 









Looking southwest.









Looking southeast.









Looking west. In this construction photo, from three years ago, There was a single crossover in the current location of the double crossover. There is now a curving tunnel heading back behind the trees where the outer loop deadends.

I hope this information helps.
Jim C.


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## pimanjc (Jan 2, 2008)

Picture with trains and double crossover.










JimC.


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## toddalin (Jan 4, 2008)

This is easy to figure out.

You say that you are using 10' dia outter loop, and that when the turnouts are back to back, you have 7" center-to-center spacing.

10 ft x 12 in/ft = 120 in

120 in - (2 x 7 in) = 106 in

106 in / 12 in/ft = 8.83 ft diameter

0.83 x 12 in/ft ~10 in.

Therefore, it works out to about 8 ft 10 in.

This would allow for 7 in spacing all around. But you may need a little additional spacing in the corners due to overhange, so may want to go with an 8 ft diameter or so.


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## sldozier (Apr 5, 2009)

Outstanding! I believe we have a consensus on "8 ft inside loop". I was kinda leaning towards 8 if I had to guess, but now I have both the science "thanks "toddalin" and "totalwrecker" and the application, thanks "Jim", to backup the guess. You guys rock!


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