Hi
What do you guys mean by easements?[:I]
An easement is a spiral curve between tangent (straight track) and a circular curve. It “eases” the vehicle into the curve. There are all sorts of formulas and methods for easements. The easiest is to draw your circular radius for your curve, then position the stratight track so it is about a 1/2 inch away from the curve (If you were using 24" radius curves, the straights would connect to a 24 1/2 in radius curve). Then form a smooth curve between the circular curve and the straight track by eye.
The next easiest is to take a thin (1/8-1/4" thick) strip of wood (like a wooden yardstick) and bend it between the straight and circular curve and use the natural bend of the wood.
Or you can draw a spiral curve on sheets of cardboard or plastic, cut them out, and use them for templates.
Dave H.
In N scale I offset my curves from tangent 3/8" toward the inside of the curve from the tangent (straight) section it is to intersect with. Then I measure 4"from the point the curve and tangent would intersect in each direction. I bend a 1/8" piece of hardboard to match the tangent beyond 4" and to match the curve beyond 4" and I trace the curve of the hardboard inbetween. It is really easy and makes the curves and rolling stock look much better.
Ron
Here’s something I’ve been unclear about concerning easements…Say I am putting in a 22" radius curve, for example, as a turnback blob at the end of a peninsula, so this will be a full 180 degree arc.
The distance to lay out this curve to the center would be the radius, which would be 22". Which would make the diameter of the full arc 44". So “on paper” this full arc of the curve should easily fit on a, standard four foot wide sheet of plywood…Right?
However, I suspect that it won’t because with easments the diameter of the arc would be MORE than 44", yes, no? Or if you did start with the diameter of the arc set at 44", the radius at the center of the arc would end up being LESS than the desired 22"?
Would appreciate an answer/explanation from all who were able to make sense of the above and understand what I’m apparently not understanding.
Thanks…
Yes, the diameter of your 180 degree curve will be greater than 44 inches. It will be greater by the offset distance multiplied by 2. When you lay out the curve you draw it completely as 180 degrees. The tangent track line is drawn so that it is 1/2 inch (or whatever offset you want) out side the curve. Then starting from the tangent track about 6-10 inches before the curve the easement is drawn between the tangent and the curve. The easement uses an decreasing radius so that it merges into the curve part way along it - about 2-4 inches depending on your technique for drawing the easement. It is recommended that the total easement length be at least equal to your longest car, say 12 inches for HO running 85 foot passenger or freight cars…
In this example the width required is increased from 44 to 45 inches. Alternatively, you can reduce the radius of the curve to 21 1/2 inches to keep the 44 inch width.
Some techniques for drawing the easement include free hand, using a template and th
So easements are really to make train operation look better?
Not just look better, but run better as well. As diagrammed in “Track Planning for Realistic Operation”, a 18" radius curve with easement causes less ‘lurch’ and coupler offset than a 22" radius curve without easement. I suspect though that as the minimun radius goes up, into the 36" plus category, this difference is less and less. (assuming HO)