Hi all -- The usual course of action when laying out the centerlines of track is to draw in the centerlines of the curves because they determine where everything else goes. The next step would be to draw in the tangents between the curves, but instead of connecting the curve lines with the tangent lines, you draw the tangent lines a given offset to the outside of the curve lines—the offset determined by the sharpness of the curve that is being joined as Dick Karnes suggested: the sharper the curve, the larger the offset. This offset allows the device (rail, wire, wood, you name it) that will be used to make the transition from straight to full curvature enough “wiggle room” to work. You might find that taking two full lengths of rail, soldering them together (with a rail joiner) to make a longer easement device, will help in the sharper curves or in those places you really want to extend the easement for appearance.
Have fun! Bill Winans (an acknowledged disciple of Dick’s techniques) -------------------------- I don't understand the offset part. Do you draw two arcs: one the real centerline and another that is 3/8" shorter radius? Why the shorter radius arc? Ben Trousdale --------------------- > ... > Any stiff, springy, straight item (a spline) intrinsically conforms to a > least-energy curve when bent and held in place, provided that you don't > over-bend it so as to kink it. One of the best items to use is a metal rail, > the stouter the better. Plot your straight-track centerline and your curved > centerine of a particular radius. Make your radius about 3/8" smaller, but > from the same center point, such that the curve misses the straight by 3/8". > Then take a yard- or meter-length of .148 or .172 rail, spike the first six > inches along the end of the straight centerline in three places, so that one > edge of the rail base is against the centerline. Then flex the rail (spline) > by hand until the rail matches your curve, making sure that you allow enough > free length to avoid a reverse curve in your spline. Spike the rail to the > curve in three places over about six inches of length. Now draw your pencil > along the rail base to create your easement > centerline. Be careful not to move the rail as you do this --You may need to > hold it down with your other hand as you draw. Resist the urge to spike the > rail along the eased curve, as this can introduce unpleasant lateral > centerline excursions. > > For curves less than 33", use a 1/2" offset. For curves greater than 45", > use a 1/4" offset. Close enough for government work, as they say... > > Dick Karnes
