The length of the easement only needs to be as twice as long as your longest car. Set the tangent (straight track) 1/4 to 1/2 in away from the curve. measure one car length of the point where those two lines are the closest and connect the point on the curve with the point on the straight with a smooth curve. Look at it. If it looks smooth it will be ok.
Dave H.
Dave H. Painted side goes up. My website : wnbranch.com
Nagrom, if you have a steel ruler in the 18" range, turn it on its side and insert it, on its side, between six or seven stout nails that hold the ruler tightly. These nails should be driven in such a way that they will anchor about 4" of the ruler along the centerline of the tangent. From this anchored end, bend the other end of the ruler in such a way that the very last couple of inches, maybe three, are aligned along the desired curve, where you'd like the curve. What lies between the extreme ends of the ruler is what comprises a reasonable approximation of a cubic spiral.
Note that your ruler, at its curved extreme, may not be all the way around the curve. As long as you can get it to closely conform to the fixed radius part of the curve, that system will work well for you. If you need something longer (not likely in your scale), try one of the items I mention below. Note also that you will want the other end of the curve eased as well, so plan for that. That is why it helps to fudge the easements in your mind while you lay out the apex of the curve first....where you want it to be....and to then go about doing the easement drawing at each end of the curve.
If you haven't access to such a ruler, use a thin piece of masonite, wooden lathe, 1/4" MDF, anything that will bend, with a modicum of resistance, and without snapping in two, to the curve you need. You could probably even get a nice piece of bristol board to do that, but I can't be sure.
Does that help?
I know this subject has been beaten to death and back, but I still just can't seem to get the whole picture. I have gotten this much so far. Ie, for my n scale layout:
I have 14" curves, so I drew a circle with a radius of fourteen inches. I think I'm supposed to have some type of flexible stick going from a point on my circle, to a point on my straight section of track. The problems I face are
1) How much does the centreline of the straight track have to be from the centreline of the curved piece of track{asumming my straight line keeps going forever, how far should this infinite line be away from the edge of the circle} (my circle on a board) and
2) How far back on the straight section should this flexible stick be?
Like I say, I know this has been beaten to death, but I have a hard time with math language, so I am hoping lamens terms will make me understand enough to lay some track. Thanks to all who can help,
Nagrom