Most of you have seen my layout design already, (but if you haven’t, look below.) I have two questions regarding building this layout after the picture…
John Armstrong recommends a minimum of 3" vertical clearance between tracks. Is this for protypical look? What would the maximum height of a moving stock actually be? Could I get away with less? I’m trying to figure out how far beneath the main roadbed I need to stick the hidden track and still have 1" blue foam sitting on top the hidden track.
My hidden track has to pass underneath a tortoise at atleast 2 locations. How deep should the track be to clear the tortoise? Should I consider using a different switch machine at these locations?
I cleaned out the room last weekend. Next week I should actually start building benchwork. (And I’m NOT looking forward to it.)
The 3" vertical clearance is part of the NMRA standard (http://www.nmra.org/standards/s-7.html). That is for bridges and such, so you will need to adjust it upwards to avoid subroadbed that is hanging down. You might be able to get away with slightly less, depending on your rolling stock, but you do so knowing that the risk is something might not pass through.
I would encourage you to stick with the 3" minimum and not cut it too close. If you don’t, sure enough, one day a MRRing buddy will come over and want to run his “rig” on your layout. Something will be different about his locomotive and it will take out the track base of your most prized tressel bridge. If’s always wise to leave yourself a little buffer.
What they said! [#ditto] Depending on the era of your RR, even the 3" verticle clearance may be problematic. Some of the newest rolling stock on prototype RRs needs higher clearance than the older stuff (just read about this somewhere but can’t find the article). This is a sign of things to come, so I would plan ahead for the future if you plan on modeling current RR prototypes. My original version of the SLO&W was set around 1900 and used very small steam locos and short cars. So I didn’t follow the NMRA standard but rather just measured to make sure those short, small things could negotiate the layout. My layout is now set in the USRA period. Still relatively small rolling stock… I have torn out a lot of scenery to accomodate the 2-6-6-2 and the 2-8-2 that now grace the layout. Now I know to plan ahead and follow the standards!!!
[#ditto] Try any way possable to keep track height clearence, even if you have to modify the swich motor to the side for clearence. I had to sacrifice a bit of height in my helix. wish I had another 1/8 or so, but will live with it…Good luck…John
Clearance questions?
For Help with NMRA Gauge letter definitions and the AAR Plate diagrams on which it’s based see: Standard S-7 Clearances and the NMRA Gauge at: http://www.nmra.org/standards/gauge.html
This should help understand why you need 3 inches or more in HO.
Digital, what will you do when you run something under the clearance and it sticks?
I went to 3.5" because, at the very least, I did not want to tell myself that I was dumb for not erring on the side of caution. At 52, I don’t need to make a younger me’s mistakes.
If clearance gets tight, or your grades get too steep, you may not be able to have the one inch of foam above the tracks - in that case, thin the foam, don’t cut the clearance! You could go to even 1/4 inch of foam mounted on 1/8 Masonite above the tracks, to keep the clearance. And a remote Tortoise mount of some sort will be essential.
