I’ve read about easements and have figured out how to turn that feature on/off when necessary using XtrkCad.
Question 1: In the picture below are points A and B the “easement” spirals?
These are sections of track that XtrkCad automatically inserted when I connected this curve, which BTW turned out to be 26" radius.
Question 2: I have searched all of the familiar web shops for 2-8-2 Mikados. I’m having trouble finding someone, even BLI, where they indicate they have them. I’m specifically looking for one in the MKT series. Am I left with getting an undecorated one and decaling it myself ?
You may be stuck having to decal an undecorated BLI Mike. The stuff listed on the BLI site is there 2nd releases. They aren’t even listing the 1st releases at all.
In you picture, yes, A & B are your easements. Actually, any track radius that is larger than your main turn can be used as an easement. For instance, 22" radius curves can be used for easements into 18" radius curves.
Tom, I respectuflly disagree a little. The idea of an easement in a model railroad is to smooth the transiton from straight to curved track (on the real railroad, they are also used to make the transtion to super-elevation, but that’s another story).
A true easement is a spiral curve that smoothly increase in radius from tangent (straight) to the desired curve radius. That makes the operation and appearance of the trains much better on our always-too-tight model curves.
In my opinion, even a relatively short spiral easement does a lot more for operation and appearance than does a chunk of larger radius abruptly placed between straight track and track of the desired radius. And usually in about the same space.
One thing that is not clear from doing easements with CAD is that one usually does not need them coming out of the curved leg of a turnout … John Armstrong indicated (and my experience confirms) that it works like an easement already. Unfortunately, none of the model railroad CAD programs with which I am familiar make it easy to take this into account by only placing the easement on the end of a curve that needs it, not both, when connecting tracks. I do manual workarounds in the plans I draw.
You are absolutely correct! [tup] I spoke a bit too rashly, thinking of a more quick fix to adding a easement to a layout rather than using a true easement, as you so aptly discribed it. Thanks for the correction. [:)]
Except, Byron, a train entering the curve from the other direction, the non-eased one, will find it an abrupt entry. So, curves should be eased on both ends if they are to be used in either direction on a class-1 type track.
Good point, depending on the turnouts. I’ve been doing a lot fo work on layouts with the traditional PECO turnouts lately (not the new Code 83 in HO) and their curved diverging leg doesn’t seem to require the easement to work smoothly. But for a more “standard” turnout with a straighter diverging leg, it’s a good idea to add the easement and the CAD programs can be used to figure it out.
I should have been clearer on that in my post – thanks!
Easements are not just cosmetic. If you have a straight track going directly into, say, 18" radius snap track, at the exact joint between the straight and curve it seems the “effective” equivalent radius is actually tighter than 18" in terms of strain on wheels and flanges. That is why a locomotive that might be able to run OK on a perfect circle of 18" radius curved track might have difficulties (including staying coupled to cars behind it) where straight track meets an 18" radius curve.
True railroad easements use an elaborate set of calculations; model railroaders tend to use templates or simple compromises (using a length or two of 22" radius curve into the “normal” 18" radius curve is a good example of that). Still others have used mechanical means, such as spline roadbed which curves with a natural easement that is pretty realistic.
What I am experimenting with on my layout (too early to give a final report) is cutting long lengths of homasote or plywood subroadbed to the exact curves I want, then kurfing the ends (sawing in parallel lines that go in about 2/3s, spaced about 1 1/2 inches apart) for about a foot and a half. It then becomes slightly bendable and I increase the radius from what it was precut at where it meets a tangent. (I wish I knew how to post a drawing so I could be more clear about what I am saying here). If you have Homa-bed roadbed that is the same idea – they have kurfed the edges so it bends slightly. That is what i do with the ends of my subroadbed. Visually, the end of the precut subroadbed looks a little like a hair comb. Is that clear?
I also have the center lines pre penciled in on that precut subroadbed so when I “bend” the homasote or plywood, the center lines are still there to help the cork roadbed be laid at the newly expanded radius. That is an accidental advantage of this system I am experimenting with.
Dave Nelson
From a practical standpoint, talgo trucks (couplers mounted on and swinging with trucks) and wide swinging couplers on long locomotives and cars are needed because of the LACK of easements. Using a gradual easement would allow equipment with body mounted couplers to stay coupled even in an 18" radius curve, assuming the equipment are all similar lengths. Likewise, an 85’ passenger car on a 35.5" radius curve will locate its’ coupler above or beyond the outer rail of the track. Without an easement, these two cars could stay coupled without any swing action.
