An easement is a gradual decrease in radius to transition from straight to curved track. One of the great advantages of flex track is the ability to add an easement to the ends of a curve. The longer the easement, the better. The hardest part about building an easement is laying it out.
Railroad engineers use complicated formulas to lay out proper easemnts. Modelers can let Mother Nature do the math for us with the "bent stick" trick.
Bent Stick Trick
Begin by laying out the centerlines for the radius of your curve and the adjoining straight track on the benchwork. Offset the centerline of the curve and the centerline of the straight track by ½ to 1 inch depending on how much space is available.
Secure a long, thin piece of wood, a 1x2 works well, along the straight centerline with nails on either side. Bend the stick until it meets the curved radius. Trace the edge of the wood to mark the line. That's it! You've created a smooth easement without any need for a calculator.
This trick will work with any curve radius and any length of track. With some practice, you'll learn where to position the centerlines and the nails for the best alignment. Always use the most gradual easement possible in the space you have available.
Sectional Track Easements
If you're using individual track sections, you can still get some of the benefits of an easement by using flex track for the easements only, or by using different radius curves. If your curve has an 18 inch radius, use a section of 22 in radius curve at each end. While not as smooth as a section of flex track, it is better than nothing.
You'll be amazed what a difference this makes in how your trains look and run.