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 Post subject: turnout radius
PostPosted: Sun Dec 11, 2005 5:59 pm 
I am trying to find out what the radius is of turnouts. I would like to keep the "turnout" part to a 28" or 30" radius, but do not know the equivalent turnout size to get (#8 maybe?)

 Post subject: Turnout Radius
PostPosted: Sun Dec 11, 2005 6:49 pm 
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Joined: Sat Aug 13, 2005 10:48 am
Posts: 365
Location: East Texas - USA
Turnouts don't have a simple radius. (At least not the real ones). Some manufacturers do use a radius - but proper turnout geometry will have straight frogs at an angle (1:4, 1:5, 1:6, 1:7, etc.) and the switch points will be straight for their movement toe to heal and offset at an angle (usually about 1:20). The divering closure radius is a product of alignment with the straight frog and the straight switch points.

There is 'equivelent' radius that includes the frog and switch rails (for fitting into a curve), but the real radius of the curved rails is sharper.

Check the actual NMRA RP12.x series of turnout dimensions and data since the FastTracks templates are constructed to these specifications.

Is your concern and 'equivelent' radius or a 'minimum' radius?

As and example: HO Number 6 (NMRA RP-12.3) -
Closure Rail Radius - 43" (note the number 5 is only about 26")

There are some 'usual quidelines' for turnouts - but each specific manufacturer and template will be unique - and all will have to be fitted in place and adjustments to the track leads made.

For FastTracks construction - you can download and print the tie templates and fit the one you want to meet your right-O-way needs.

Curving trunouts will be a different set of principles - generally you get a smoother and gentler curve - but at the cost of carefull hand construction and/or adjustments. (Download the twistties manual and see how the curved construction progresses). Also, Tim just released an alternative method for curved turnouts in his latest news release.

-ed mccamey-
NMRA Standards and Conformance Department
PROTO & FINE Scale Coordinator
I estimate I have about 5 pounds of coupler springs somewhere in the vicinity of my workbench.

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