Fast Tracks

I am in the process of building an Sn3 layout and am using mostly TwistTies for my turnouts. There is a place on the layout that would be best to cross over on a curve. The inside curve is 30" r and the outside can be much larger than that but it will have to spiral in to go no larger than 36" I plan to use #8 twist ties for the turnouts. I'm having a little trouble with the geometry and I would welcome any suggestions on how to set these turnouts up.

Thanks

Jim McHenry

Jim.

Twist ties turnout bases allow full curvature (within reason). 30" radius to 36" radius crossovers with number 8 bases is very reasonable.

At issue is the direction of the cross over portion and the required separation distance between the two turnouts. On a curve the total crossover length can become very space consuming. You'll be curving the straight portion some and the diverging portion of course even a bit more.

For a 30" on left to a 36" on the right crossover the left turnout need to be a RH - curving the diverging portion at 30". The left turnout needs to be a LH - curving the straight portion at 36". The crossing proper needs to be a smooth transition between the two and likely the switch point to switch point separation distance would be close to 32" to 38" (only an on site alignment can be correctly assured). This makes the internal crossing track from frog to frog in excess of 20". You can likely get the two radius to something like 30" and 34" and lessen the separation distance some.

The crossing in the other direction would be inverted types - distance still the same.

Layout your minimum radius - pin the twist tie to the curve. Layout the second turnout - pin the flex tie to that curve and move the separation distance on both until a nice smooth transition of the crossing track occurs. Don't try and squeeze the turnouts closer together - you'll end up with a kinked crossing.

_________________
-ed mccamey-
COSLAR RR - http://www.coslar.us/
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.