# Long S



## Xiong (Jul 15, 2011)

I'm planning a Free-mo module; I'm hoping to work to high standards. Right now, I'm drawing in XTrkCad. I'm stuck on the double track mainline. 










My module ends are angled at 5 degrees to one another, which I hope will introduce some variety in contrast to straight-as-an-arrow mainlines. But this causes difficulties, too. I curve both tracks close to one end and put in a couple of turnouts. I can't build both curves the same; if I did, I'd violate clearance on the curves for Class Ia equipment. So, by the time it all shakes out and the tracks are perpendicular to the far end, one track is offset -- by less than a quarter inch. I need to insert an S curve to bring the centers back to 2" at the far end. I have over three feet in which to do this. 

Free-mo requires 12" of straight track between reverse curves. My difficulty is that if I angle the straight even so much as a single degree, the difference in ends is more than a quarter inch; and that's not counting the curves themselves. And a 0.5 degree, 96" radius curve is not even an inch long. 

I'm coming up with silly-looking solutions. It would be much easier to deal with a 1 or 2 inch offset. But for other reasons, I'd like this nearly straight. 

So, my question: If I go to a sufficiently high radius, can I legitimately dispense with the required straight between reverse curves? Two curves, each 2 degree, 200" radius, seems about right. And if not this, then what? 

I realize that if I were just monkeying around, I could easily wiggle a piece of flex track into such a slight S. For a serious layout -- and one that will be critiqued -- I'm looking for the legitimate solution.


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## tjcruiser (Jan 10, 2010)

Not to sound critical, but what's the downside to using a piece of flex with a very soft inflection (S) curve? It seems to me that that could offer your most gradual / easy-running transition between the two straight sections of track?

TJ


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## Xiong (Jul 15, 2011)

Building a module means offering my layout to any number of people I may never have met before, some of whom may be real sticklers for standards. I'd hate to drag a couple of modules a few hundred miles; only to find that the guy who passes final judgement on acceptable modules in that town finds my trackwork shoddy. The only real defenses I have against that are to hold up my plans to community scrutiny well ahead of time; and conform to published standards as closely as possible. 

I see trouble with the general approach of nailing down a piece of flex and saying, Well, that seems to work. I cannot then point to a drawn, measured plan and show both that the plan conforms to standard and the track conforms to plan. 

I'm not the sort of person to lean on another fellow on technicalities; but such guys are out there and I'd prefer to stay a step ahead. If I can't find a published exception to the foot-long straight rule, I'd like at least the backing of experienced modelers who agree, more or less. 

Ah, please note that when laying track, yes, in any case I would do this long S as a single piece of flex. The point is, How do I shape it? Any flex on my layout, I want to nail accurately on top of defined curves. It might look like two curves with a straight between but in practice, of course, it would all be flex; and as much as possible, continuous. 

Thank you, though, for the reassurance. 

Thinking it over, I relaid the area near the endplate (beyond the left side in the figure above) and eliminated the offset. With over 2" center-to-center on a 138" radius, I guess that's okay by NMRA S-8 (although not 100% legit). And with the offset gone, no worries about a long S. 

I'll post something better developed when I have it. Thanks.


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