I have been viewing the foum for a while, but this is my first question / comment. I have just started getting back into HO model railroading after a several year break during a house move and while my sons were young. I am building a 16 x 10 layout modeling the Western Maryland in the late 60’s.
I have two quick questions which I’m sure someone will be able to easily answer:
With Atlas sectional track, does the radius distance refer to the midpoint between the rails, the inner rail, or the outer rail? In other words, what is the outside rail radius of a 24" radius sectional track, 24 inches?
With Atlas flex track one rail is fixed to the ties and the other rail slides with the ties as the track is flexed. When laying a curve should the fixed rail side of the flex track be on the inside of the curve, outside of the curve, or does it matter?
All measurement are from the ‘centerline’ of the track. There has been a lot of discussion about which side the 'sliding 'rail sould be on - I really do not feel it makes any difference. I have about 200 section of flex laid whatever way is best - after 17 year, I have had no problems!
I think the ‘preferred’ method of laying flex on a curve it to have the fixed rail on the outside so that it is the longest of the two rails. Then you cut the other to fit. However, I have about 200’ of it laid both ways,as was mentioned earlier. I don’t think it is that important, but what I said earlier about the longer rail being on the outside, is the reason for doing it that way. You may save a few inches of track doing it this way though.
Doesn’t matter which way you put the sliding rail on flex track.
Either way one rail will be 36" (the outside rail) and the other rail will be shorter (the inside rail). You niether gain nor lose track length.
The real difference is tie spacing. On the fixed side all the ties are connected by plastic uner the rail. on the sliding side, there are gaps under the rails.
If you put the fixed rail on the outside then the ties will be “compressed” on the inside of the curve. If you put the sliding rail on the outside then the ties will be “expanded” on the outside of the curve.
If you use Micro Engineering flex track where ther is no sliding rail then the ties alternate connections and it doesn’t matter.
Thanks for the quick answers on the radius and flex track. That was exactly what I was looking for.
I plan oh having a 22" radius as a minimum radius in a few spots, but most turns will be 24" or larger. How tight a radius can fles track bend before it starts to kink? Can you bend flex track to 22", or am I better off going with the sectional track and sodering the extra joints? I’m not too concerned with the less than prototypical look of the sectional track on those few 22" turns.
Theoretically, and with the right skill and implements, one should be able to get flextrack down to a radius of an inch, maybe even less. Of course it would be ridiculous, but flex can relatively easily be radiused down into the 10" range. The technique is to actually bend the metal so that it wants to stay bent. You must modify the tie structure to spare the spike heads from the popping forces they’d incur, but if you can get the ties to compress sufficiently, that would determine your limit…not having to cut ties or pare them severely so that they would be close enough together inside the radius (at the inner rail) to show a decent curve.
I have bent flex track down to a 12 inch radius without a problem. I also have an assortment of snap track curves of various diameters. I put then together and lay then out and use them to mark the track center line for the roadbed and flex track.
Track radius is measured at the centerline. If making track templates to butt up against the ties, the curve of a convex template should be the radius less 1/2 the tie length and the curve of a concave template should be the radius plus 1/2 the tie length.
I put the fixed rail on the outside of the curve, which just seems more logical to me. I don’t clip the rails to make the joints come out together. Rather, I slide the loose inside rail into the ties on the next section of flex and install a joiner wherever the end happens to fall. The way I lay track, very few rail joints fall at the same pair of ties, even on tangent track. (My prototype, OTOH, ‘squared up’ rail joints so they fell together on a pair of closely-speced ties. Go figure…)
As I type, there’s a piece of Atlas Code 100 flex, pre-bent so it would relax to a radius of 350mm, sitting on my worktop, not attached to anything. It has held that radius for about a year and a half now…