Loose rail in Atlas code 55 flex track

[mark.hinds]

The quote below was posted by Randgust on Railwire a couple of years ago.  I am concerned about the single loose rail in Atlas code 55 flex track, and have 2 specific questions for those of you who have had it installed on your layouts for several years (newly installed doesn't count):

1) Have you seen gauge changes on curves due to temperature variations?
2) Any other thoughts as to whether the loose rail should be on the inside or outside of a curve? 

Much of the 'newer' C80 and probably the Atlas C55 is very flexible, one friend calls it 'spaghetti'.   Nice to lay and not kink.

But after you put it down, that flexibility allows it to be subject to heat expansion/contraction that is DIRECTLY transferred to the gauge on curves.   I've certainly seen it.   You may never notice it go wide, but I bet you'll notice it tighten up when it squeezes Kato six-axles off of curves.   It will vary the gauge before it changes length at expansion/contraction joints, the gauge is the point of least resistance.

Thanks in advance,
Mark

[mark.hinds]

Interesting...  Based on crude experiment, loose outside the curve widens the gauge, and loose inside the curve narrows it.  My previous questions still stand though. 

MH

[Chris333]

I bought a big case of newer C55 flex that had one loose rail. Ended up using the whole case as rail to build turnouts.

[ednadolski]

I haven't had any issues with the gauge.  Luckily, the temp & humidity in my basement are pretty even. What kind of swings do you expect?

I put the loose rail on the inside, since I find it easier to trim and install that way.  I do leave a small (.010" - .020") gap  between every rail (so each rail gets a feeder wire).  I also stagger the gaps by about 1" to reduce the chance of kinks.

I always use brand-new joiners, throw out the old ones as they are worse than useless.

Ed

[ednadolski]

loose outside the curve widens the gauge, and loose inside the curve narrows it.

How much difference from nominal do you see for each one?  As long as it is within NMRA tolerance, the tighter gauge is theoretically preferable (unless you have rigid, long-wheelbase locos with not enough sideplay in the axles).


Ed

[rschaffter]

I recall that when handlaying track with a 3-point gauge, one should put the double-pronged side on the outside, to widen the guage slightly, but AFAIK the prototype maintains a constant gauge through curves. However,  they use broader curves, much smaller flanges and equalized trucks (and much more favourable physics!), so they don't need to worry about the flange edge contacting the railhead as we modelers do..

[mmagliaro]

They all have one rail looser than the other so that the flex track can bend.  I always put the loose rail on the outside
of the curve.  The loose rail is not gripped as tightly in the tie plate detail on the ties.  So under pressure (when bent around a curve) the looser rail is going to always push toward the outside of the curve.  If you have the loose rail
on the outside, that means it will be pushing away from the center of the track and will slightly widen the gauge.
If you have it on the inside, it will be pushing toward the center and will narrow the gauge.

Given the choice, I would always choose to let it slightly widen the gauge on a curve, hence I put that rail on the outside.
I've had too many painful experiences with the old code 80 track where the narrowing on a curve would be enough to force
long-wheelbase steam engines up and out of the rails.   The code 80 would be too narrow on the
NMRA gauge plate.  I don't know if the code 55 would squeeze that far, but I don't want to find out after the track has been down for 6 months and covered in ballast.

[sp org div]

Hey Mark,

Never seen the gauge change noticeably since I glued 100'+ of trackage down in my curved staging yard a couple years ago....  but the loose rail on my order of flex track was more than loose.
I laid mine with the floppy rail to the inside, and the tightest radius turn is about 22".  The NMRA gauge shows the rails on the wide side, but my ME track gauge is a better fit (but rails are still a bit too far apart).  I soldered the rail ends together with gaps about every third section (multi feeders), but the floppy rail popped up and out of the ties when the ambient room temperature rose more than 25 deg above my building spec of 70 deg (the central air failed).  It did snap back into place with no further issues to date.

Jeff
http://espeeoregondivision.blogspot.com/

[mark.hinds]

Thanks for all the replies so far.   

How much difference from nominal do you see for each one?  As long as it is within NMRA tolerance, the tighter gauge is theoretically preferable (unless you have rigid, long-wheelbase locos with not enough sideplay in the axles).

Ed

Ed:  I was bending the Atlas code 55 flex probably more than my minimum radius of 16", with the loose rail on the inside of the curve.  The NMRA gauge showed it was still in gauge with a little extra space, probably because the track is a hair short of being over-gauge when straight.  In fact, when Atlas code 55 flex is straight, when I push down with the gauge, it pushes the loose rail aside and drops down along side the rail.  I am assuming that this behavior (when straight) is not an issue with properly-gauged wheelsets, as if it was someone would have mentioned it in the Forums. 

Mark

[Chris333]

I should also note the track I had the rail was so loose it would fall right over and out of the tie/spikes. I didn't have any gauge problems because I didn't think it would hold up and tore it all out before running trains.