Easements in my experience are best performed free flow. True easing is a continuous change in radius. Classical methods are the bent stick, using a bit of flex track, and the ever unpopular mathematical layout and plotting.
For a fixture - use any close approximation that pre-bends closely - but solder the PC ties on only one rail - gently lay in place - for second rail and use gauge to solder in place the second rail. Pre-bending a smooth curve in the rails.
Not exactly a cookie cutter approach - but far better operationally. It would be possible to CAD a series of segments giving easements and create fixtures - but the differing combinations of start and end radii and varying lengths would be a large number of combinations - making production (and option purchasing) an expensive nightmare.
-ed-
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-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.