I have been considering using N Scale roadbed turned upside down as the spacing between my double track mainline, I have noticed that the center between a two track main isn’t anywhere near as pronounced as it is on the outside of the tracks and my thinking was that this would not only elevate the area between the tracks but would also provide an easy way to keep the spacing even. My mainline curves are a minimum of 48" radius so I don’t think I would have to expand the spacing on curves particularly.
So … when all the smoke has cleared, what centerline spacing does this idea create? A mechanical means to govern the spacing makes sense – but having a centerline that looks realistic given your impressive minimum radius should be the prime directive.
By the way, railroads had and presumably still have very precise standards for the contour of the area between the two main lines (as they did and do for the contour beyone the rails). I researched this on the C&NW some years ago and back in WWI days it was almost a trench it was so deep. Over time the standards changed to build this up into something closer to even ballast between the ties of the two mains - only a very slight depression, but again carefully measured in the drawings.
This is conjecture but perhaps the assumption was that back in the day the crew would walk on top of the cars rather than get down on the ground and walk along the cars.
My own research by the way showed that I did not have to widen the 2" spacing I chose on my double track main down to about 38" radius. But 2" is wider than many prototypes – as i realized when my first mock up of an important bridge constructed to exact prototype dimensions clearly was not going to work. Doh! I knew my spacing was not prototype based but I did not apply my knowledge …
I’m w/ Dave on this one. Just what spacing does this end up? Don’t have any N roadbed or know the width to check. As Dave mentions, even @ 2" this may be much wider than prototype, however, for our needs tend to work out. Also, many running 2" on the straight mainline may need to widen the spacing as the track eases into turns for clearance on tighter/ smaller radius on the turns. A track spacing of 2 1/4- 2 1/2" recommended for smaller radii under 30-36". This will vary pending your equipment length and pilot overhangs.
If the N roadbed does work out to close to the 2" spacing, I could see it used as a tool to aid in laying your roadbed, but wouldn’t glue in place. It could be placed if your ballast profile calls for, but if any between track depressions are needed just carve or leave out.
Well, I think the spacing is about 2" or so but my thoughts for the center was an “access” road like you see on most railroads, usually running alongside where a third track was or in the middle where a third track was located. At any rate it wouldn’t dip down so deep as if there was nothing there at all plus it would make it a heck of a lot easier to maintain spacing on my mainlines. I’ll be running everything from Big Boys to GE 44 tonners depending upon my whim so maintaining the same spacing between tracks is one of the ideas behind this, aside from the fact that I think it will look better as well.
Now this is just for the double-track mains with the possible exception of the yards, haven’t quite decided how I want to do that as yet.
If you’re going to run large steam (Big Boys, Challenger, Yellowstone , you definately need to open the turn spacing to at least 2 1/2". Check your clearances by mock up and place the steam on inside and a passenger or autorack on the outside. The rigid frame of the “Big Boy” will allow some serious overhang into the turn, spacing under the 2 1/2 can cause sideswipe of a very long piece on the outboard track. The problem gets worse on smaller radius esspecially under 30".
On my layout I run Mallets and 85’ passenger cars and I run double track mains on most of the layout and a short stretch of 3 track and I keep the spacing between the tracks at 2 1/4" on the straights and 2 1/2 on the curves. This give me enough clearance on the curves without sideswiping each other on opposing trains and still look fairly close to prototypical in appearance. I run 40" radii curves on the mains and 36" radii on the secondary lines where the big steam and passenger cars will run and then I have some curves that are tighter but are restricted to smaller engines and passenger cars. I took some balsa wood and cut grooves into to it so that it could sit on top of the rails and give me the exact spacing needed and it was my guide when laying track. But I would not go under 2 1/4 between the straights and 2 1/2 on the curves. Hope this helps