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Quick background: I've never gone beyond running loops on carpet but have aspirations to eventually build a spare bedroom layout in the coming years. I thought that building a Christmas layout would be a good primer. Here are the basics:

  • Corner layout limited to 5'2" in width because of a decorative fireplace mantle;
  • Emphasis on action (simultaneous two train ops) and whimsy;
  • MTH RealTrax since I have a fair amount already (O-31 and O-42);
  • Polar Express LionChief RTR plus another RTR consist (short, light trains);
  • Two layer layout made from XPS foamboard and Great Stuff spray foam;
  • Trains can switch loops but will stay on their own loop/level 95% of the time;
  • 6" rise from lower to top level with 4" clearance at tunnel portals (from top of rails);
  • Artificial tree with "trunk" going through 2-3" hole in the top layer.

Last night I played with SCARM for the very first time and came up with what you see. I still haven't figured out how to do inclines so I had to rely on color coding:

  • All green is at floor level;
  • Pink (main upper loop) and purple (trolley loop) is at second level;
  • Light-to-dark of same color represents tunnel beneath second level;
  • Teal is the principle grade between levels;
  • Orange is for going down only (steep!) but allows for PolEx to run unattended using both loops (from bottom clockwise - lime green, teal, pink, orange, dark green, lime green, teal, etc.) while second train sits on floor level siding (lime green).
  • Track footprint is 55" wide by 59" deep with room corner in the upper right.

I welcome all thoughts and suggestions!Christmas 2020 v3




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  • Christmas 2020 v3: Christmas 2020 RealTrax Layout
Last edited by James in VA
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The passing siding is really nice.  I would say it's a lot for a small space.  The biggest red flag I see is the Polar Express.   Because I learned the hard way there is a reason the PolEx is rated for 036 track.  On O31 the front truck tends to short out out or jump the track.  Please check the box it came with to make sure you know the minimum radius before setting up 031 and driving yourself nuts trying to figure what's wrong with the engine.   


@jhz563, many thanks for pointing out the potential problems with the Polar Express set. Being a Lionel RTR set, I figured the loco would run on anything O-27 or larger. I did a Google search about its minimum radius and one of the hits was this really interesting OGR thread from @Moonman entitled Learning the hard way which chronicles his trials and tribulations of building an ambitious Christmas layout. 

Dang phone - my long reply disappeared. 

Good points in the other thread. 

Grade changes need a gentle lead in.  Any time you can get some straight track at the bottom of a grade it helps.

Split the power feed for uphill and downhill sections.  Use separate power supplies so you can manipulate the voltage.   The old school solution is to use a rheostat. That way you just use one power supply but can reduce the voltage on the downhill run.  Both methods work.


I took the guidance to heart and saw what I could do using O-42 as the only turn radius (aside from the trolley loop). I wish I could figure out how to do inclines and levels in SCARM so what you see is just a top-down view. I know it will be limiting but I only want enough vertical clearance on the tunnel portals to allow for the RTR PolEx with 1/2" clearance. That is to lessen the grades. The orange grade is essentially down only but hopefully allows for PolEx to run unattended using both loops (from bottom clockwise - lime green, teal, pink, orange, yellow, lime green, teal, etc.) while second train sits on floor level siding (lime green and yellow). Simultaneous two train ops (unattended) would have one on the upper loop (pink) and one on the lower loop (lime green and yellow).

I did end up with three slight disconnects but these are all about 1/4" so they should be made to work using just a bit of play. I've also provided the SCARM file in case someone can help with adding the inclines and upper level (all pink and purple).

Many thanks!

Christmas 2020 [42 min)



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  • Christmas 2020 (42 min)
Files (1)

One thing I recall is I was making grades on their own layers, and each level or block on their own (flat) layers, so I could easily tell where one line ran directly over another. Learning to make objects takes learning the elevation coordinates and is very similar in concept to grade coordinates. (your already doing things in x&y, not z )

I ended up starting with grades to get the transitions the way I wanted vs automatic

@Adriatic, many thanks! I fully understand conceptually. My problem is figuring how to do elevations in SCARM (tried for the first time Wedneday night). Everything that is yellow or green is flat and on the first level. Everything that is pink is flat and on the second level. I want to minimize the elevation of the second limit due to the grades. All the portals but one have the lower track at "sea level" passing under the flat second level. The exception is the down grade where orange passes under pink. That will be the tightest vertical clearance. I envision the plane of the first level being exactly 4.5" (3 x 1.5" layers) below the lower plane of the top layer of foam board (1" thick). Minus the track thickness leaves me about 4.25" from the top of the lower level rails to the portal. Where orange passes under pink, I'll have about 3.75" of clearance. That means about 8' (96") of run to drop 5" of elevation making this downward grade a tad over 5 degrees. The worry is what will happen to the PolEx when it reaches the yellow 42" switch (on the left). Any thoughts?

The SCARM file is just above if anyone can lend a hand there!  :-)


Forgive me for butting in, but this will not fit in a 55" x 59" space.

I didn't understand how 3 layers at 1.5" were used to determine the height, so I did this version with the upper level and trolley loop 4.5" above the base. A quick search didn't find the height of the PE engine, so I'm not sure that's enough with tracks and upper level decking. Though the photo shows just the tracks, the tracks in the attached file are set to Bridges w/o supports so you can see the separation in the 3D view easier. Various sections have also been placed on different layers so they can be turned on/off. I didn't mess with setting tunnels or adding objects for decking. I'll be more than happy to help you with learning how to set grades, etc.

Anyway, the thing about clearance is it needs to be wherever one track overlays another, not just between levels.

As you can see along the left and top, the upper pink tracks overly the lower blue track over most of the grade and there are places where clearance is than 1.5".

The outer blue grade tracks along the top are too close to the lower level green tracks, trains will hit the tracks.

The inner brown grade tracks are also too close the the upper pink tracks and clearance over the green tracks is also less than 4.5".

The purple trolley loop is also too close the pink upper level tracks.

Christmas 2020 [42 min)



@Mixy: Many thanks for the SCARM tips and links!

@DoubleDAZ: Very grateful for your "butting in" with all your expertise and suggested design. I'm a former Navy submariner but Fly High my USAF brother!

I was out of state visiting Mom and just got back. I made a lot of changes using RealTrax and got close but was still having problems fitting a 2 train, 2 layer interconnecting layout to fit in a 5'2" width. That said I tried Fastrack (which I have some of) and came up with what you see here. The short orange grade is for going down only (steep). The blue grade can be used in either direction. Again the idea is that two trains can run simultaneously while staying on their own levels (for my daughter and I). Or, the PolEx can run unattended using both loops going from blue (up grade) to pink (top) to orange (down grade) to green (lower level) while popping in and out of view a number of times in a single trip. Meanwhile, the second train would sit on the lower level siding.

I gladly welcome any and all thoughts! Oh, and only four months until Christmas!  :-)2020.08.18 Christmas [Fastrack 36) 2D2020.08.18 Christmas [Fastrack 36) 3D Top2020.08.18 Christmas [Fastrack 36) 3D Front2020.08.18 Christmas [Fastrack 36) 3D Rear



There are a couple of areas where I don't think there's enough separation. In the top circled area, the brown grade varies from about 3.5" to 4.25" above the green bottom track, so even without sub-roadbed, the engine and cars are going to hit. In the bottom circled area, the separation between the purple tracks and brown tracks by the switch varies from about 4.5" to 5". Also, the grade ends inside the tunnel and depending on the opening, the tops of boxcars could hit the sides of the opening.

2020.08.18 Christmas [Fastrack 36)

Here's some suggested changes. I rotated things 90° to get a larger workspace on my laptop. The dark blue tracks are at 6" and the single dark blue switch is at 5". You can see the grades and I ended the brown grade before the tunnel. Unfortunately, there is still only 4.5" of clearance beneath the turnout and I'm just not sure that's enough. You can changed the height of the dark blue tracks to 6.25" and that will change the grades to 3.7% and 2.7%. Just food for thought........

2020.08.18 Christmas [Fastrack 36)daz


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