Hello guys, I was looking around the internet because I'm undecided whether to use Kato (or something German because the price would be lower) or Atlas Code 55 (for reality) for N scale planning. I came across some pictures showing tie spacing in the USA and it seems that some parts doesn't have the normal tie spacing (e.g.: http://c8.alamy.com/comp/EB0NWD/american-railroad-tracks-new-orleans-usa-EB0NWD.jpg instead of the correct one: http://c8.alamy.com/compde/dhk7rb/l...in-gleis-verschwindet-in-die-ferne-dhk7rb.jpg) Is this just an exception? Are american tracks so tight because of the train's weight?
The first photo appears to be trolley or interurban track, thus light rail loading. The second photo appears to be Class-I mainline track, thus 100 or 120 Ton car loading, and 200+ Ton engine loading. Just a guess, mind you, but the second photo looks the same as the CSX and KCS tracks in my area.
It depends upon the application and maintenance. When first done, all is essentially perfectly spaced. (This being on current light rail commuters and heavy main track freight/passenger.) If not well maintained, ties can move around and.... On older branches, lighter railed, etc, spacings can really start to stray.
The first shot is definitely passenger light rail - look at the overhead catenary. For US freight trackage, the math 'more or less' works out to evenly spaced ties under a 39' jointed rail length - which is US standard, ensuring you have a good solid one at the joint if not two. So the typical main line tie spacing typically runs around 21-22 inches, but I've seen it go as low as 19 and as high as 24. It also depends on the ties as those aren't necessarily the same although a 7x9 is typical. Tie spacing is measured 'center to center' and will usually vary within an inch or so. Ties will move around a bit, but current track safety standards really focus on the placement of solid ties around the rail joints, so figuring that you 'must' have a good joint tie, and also accommodate rail stagger, you begin to see some spacing patterns emerge that rarely get violated today. Rail anchors are to keep ties from moving around much (particularly on welded rail) and to keep the spacing intact due to load shifting, heat kinks, etc. There have been historic exceptions - as a Santa Fe modeler it was obvious to me that the mainline seemed to have somewhat smaller and closer-spaced ties 'back in the day' and I was told that their usage of softer pine for ties resulted in both a somewhat smaller tie and closer spacing than would normally be seen (remember they had their own mills in Louisiana). I've also seen secondary track on an ex-Southern branch that had deliberately skewed ties on the rail joints where two normal ties had been taken out and one skewed tied replaced, which was OK until that one tie failed and then you really had a mess. As wheel loads have increased, the focus has been on heavier rail and better-condition ties, not spacing them closer together. I'm seeing 286K cars running slowly over old 85-lb rail, but you're seeing that track with superb tie condition and good ballast and not over 15mph. I've seen unit frac sand trains absolutely chew up lines with poor tie and roadbed condition with light rail, only takes about three bad ties in a row and you're looking at a potential rail break in the old light stuff. But in all those cases, the original legacy tie spacing usually carries forward. There's a lot of formal studies out there on the relationship between wheel loads, rail size, speed, impact loads, and tie spacing if you dig around for them. There's also a tendency toward maxing out the spacing to 24" with concrete ties and heavier rail, although you'll find a lot of debate about that. Most US railroads have very specific design guides online how to build industrial sidings to their specification to be able to serve them, this is just one example: https://www.cn.ca/-/media/Files/Cus...ifications-for-Industrial-Tracks-en.pdf?la=en
Check this out: https://www.nmra.org/sites/default/files/d9n.pdf https://en.wikipedia.org/wiki/Railroad_tie It's an NMRA guide that reflects typical practices. Era and traffic density (mainline vs branchline vs oddballs like interurbans and trolleys) affect modeling tie spacing. Operating speeds too. Not knowing what line you're modeling it's impossible to say which track approximates the look you'll need.
