HO Turnout specifications

[jjqgenesis]

Hello,
I belong to a new RR club and we are preparing a trackplan for submission to the members for approval. I need to know the specifications that determine what number a turnout is. No. 4 vs No. 8 etc..
I have visited web pages over the years where this is explained with detail drawings but can't locate any of those addresses.
Appreciate your help.
Thanks.

 

[marty w.]

Hi jjqgenesis,
This is from the NMRA site on standards for turnouts. Hope this helps.
http://www.nmra.org/standards/rp12_3.html
Marty

 

[Roger Hensley]

Good advice to visit the NMRA Standards.

A quick explanation is that a number four turnout diverges 1 foot (scale) to the side for each 4 feet forward. A number 6 would be 1 foot to the side for each 6 feet forward. That's where the numbers 4, 6, 8, etc. come from.

In point of fact, there is more to it than that as the actual frog angle (where the rails cross) is measured in degrees. An Atlas 'Snap Switch' is designed to mate up with 18inch radius track and doesn't really fall into the number 4 or 6 category. The NMRA does have turnout templates available as well as putting the Standards and Recommended Practices on line for you.


Roger Hensley – madisonrails@railfan.net
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