superelevating the roadbed or the track?

Model Railroader General Discussion (Model Railroader)
1

Hi all,

Sorry for all the questions lately, I’m actually starting to make progress on my N scale layout and the further I go along, the more I find that I don’t know. Anyway, I’m going to use .030" styrene strips to superelevate my track and I’m wondering if it would be better to place the shims under the track or the roadbed. I’m using Woodland Scenics foam roadbed and Atlas code 55 track.

Thanks in advance.

2

Technically, you can do either. I would prefer the shims to be under the roadbed, as this will be a stiffer and more even surface on which to fix the ties.

You should have an easement into the superelevation, just as you would a vertical curve or a horizontal one, even though you are only elevating the one of the rails. Give this some thought since you have tentatively identified 30 thou as your elevation…what will you use to get it to 30 thou over, say, 8" on either side of the curve? I suggest layers of strips of masking tape overlayed when you need it to get the additional height.

3

I work in HO, but the overall methods should work in N. I used 3/32X1/4 stripwood under the outside rail. The key is a VERY gradual transition ffrom flat to elevated. I tapered the stripwood for a length of about 18" and stated it about 6" into the tangent.

4

I shimmed under the track rather than the roadbed…

A word of caution, though… If I had to do it again, I’d have used cork roadbed rather than WS Trackbed. The foam WS stuff is so soft and spongey, it absorbs the shims somewhat. Cork wouldn’t do that.

My maximum superelevation is 0.020", with 0.010" in the easements.

5

Technically on the prototype I believe it’s superelevated at the subroadbed level, so putting the shims under the roadbed would be a bit more prototypical. Once you ballast the track I don’t know that it would make much difference in appearance though.

6

I am in HO and am using a product from PSC that is flex track with the superelevation built into one edge of the ties.

It works well and looks good BUT two problems arise. One is that if you nail your track down, the tie is elevated a bit in the center and the tendency is for the nail to depress that tie – and that in turn tends to bring the rails in together changing the gauge. And a curve is exactly where you do NOT want tight gauge.

The second problem is with ballasting – now one rail and the end of that tie are more or less up in the air which makes normal ballasting techniques all the more challenging.

the ultimnate would to be to superelevate the subroadbed. One idea that struck me were I to do it over again – use Woodland Scenics black foam roadbed material but cut it in strips like cork roadbed so that two halves make up the roadbed. Use their “N scale” thickness for one strip, and their HO thickness for the other. I have NOT tried this – this is pure “vaporware” but it might work. In fact it might work for both scales

Dave Nelson

7

Thanks for the replies everyone.

I guess I will be elevating the roadbed since ballasting will be easier. I forgot to mention that I will be using .010" strips a little before the curve starts, then .020" and then finally .030" and each transition will be spaced about 6" apart. I originally got idea from Dave Vollmer so I assume if it worked for him I can make it work too. I know that .030 is a little too much elevation (that’s 4.8 scale inches) but I think that the foam roadbed will absorb some of the extra. I like the idea of masking tape layers but when I tried to form the stuff around curves it wrinkles to the inside. I know a thinner tape will solve this problem but I don’t feel like buying more tape when I already have the styrene strips (I know, I’m cheap [:D]).

8

Hi “CSXfan,”

I superelevate the track using shims under the ends of the ties. With flextrack I like to use plastic shims that I can cement to the ties, although it usually takes something like Plastruct’s PlasticWeld to make the bond. For handlaid track I glue stripwood shims to the roadbed before gluing down the wood ties.

Shimming under cork or foam roadbed I find less satisfactory because the roadbed isn’t rigid and doesn’t form an even surface when shimmed. Then if the track isn’t laid exactly matching the curvature of the roadbed, the superelevation isn’t even. Superelevation under the ends of the ties always matches the curvature of the track.

I like to use superelevation along with easements (transition curves), arranged so that the transition from level to superelevated track takes place along the length of the easement.

So long,

Andy

9

I agree, I shim underneath the track, because I have Woodland Scenics foam trackbed. If I had put it under, the foam would have really absorbed the shimms when run over.

It does help after you ballast though.

10

Superelevation looks very impressive, and I certainly appreciate it on layouts but, modelers should be aware that if their cars are not weighted properly or have wheel/coupler issues…weird things can happen on these curves (at least from what I’ve seen ).

I live near the CSX mainline where trains blast by at 60+ mph speeds. It is a cool sight seeing Amtrak and CSX trains “hanging 10” on the superelevated curve there. Those locomotives and cars really lean into it!