# ?Whats the difference? -- Switch / Turnout Size Numbering



## MBlair (Mar 19, 2013)

What is the difference between #4 #6 #8 turnouts?


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## D1566 (Jun 8, 2012)

The number defines the radius of the turnout. The higher the number, the larger the radius is (and thus more realistic, and better for long locos to negotiate).


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## broox (Apr 13, 2012)

more speciffically, the number represents how tight or ... un-tight the radius is.

so a #4 there is 4 units (cm, in, m, etc) of length diverging track until it is 1 unit away from the main.

so a #6 or #8 is 6 or 8 units length until its 1 unit away from the main.

bigger is better, baby


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## rrgrassi (May 3, 2012)

#4 typically follows the 18" radius. #6 follows the 22". I never used a#8, but my guess is that it follows a 24" radius.


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## broox (Apr 13, 2012)

I'd think #6 is more 24-30" and #8 are more in the 30-40" range.

Although its not quite right, because the diverging rail is straight, not curved


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## Pfunmo (Feb 21, 2013)

Or another way to get it in mind without bothering with the facts? 
Think of them as 40, 60 and 80 MPH curves! The long lean 80 MPH may look and operate nice but boy they take up the space!


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## waltr (Aug 15, 2011)

broox said:


> I'd think #6 is more 24-30" and #8 are more in the 30-40" range.
> 
> Although its not quite right, because the diverging rail is straight, not curved


A prototype switch (turnout) does have a straight diverging rail. The number is the ratio of the run verse separation of the diverging rail to the straight rail.

In this link:
http://www.nmra.org/standards/sandrp/rp12.html

The turn-out number is the dimensions 21 divided by 23.


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## cv_acr (Oct 28, 2011)

Not the radius. It's a ratio representing the frog angle. The bigger the number the longer and more gradual the switch is.

The Atlas SnapSwitch that replaces an 18" curve is "approximately" a #4 1/2 switch.



broox said:


> so a #4 there is 4 units (cm, in, m, etc) of length diverging track until it is 1 unit away from the main.



broox's description is accurate.


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