N Scale Cajon Pass Model Railroad Project Part 3 – Backdrops and Roadbed

This page is one in a series on the buildout of an N scale model railroad depicting the Cajon Pass area in Cajon, California. We are modeling from roughly CP Walker to Sullivan’s Curve.  You can find the main table of contents for all the articles in the series HERE.

Welcome to Model 160 and we hope you enjoy the project!

Moving on, the next bit to work on is to wrap up the backdrops and start getting roadbed down.  First the track plan for reminders:

When we left off in the last update, the masonite hardboard backdrops are up and the next step is lightweight flexible spackle to hide the seams and flush screw heads. The particular spackle I use goes on a pink color when its wet and dries white which is a nice way to have some idea of how much things have set up. I still generally wait overnight before sanding as you’ll have a big mess on your hands (and sand paper!) if you try too soon. As an intermediate step I usually take a wet smooth cloth, wring it out and wipe down the first coat of spackle. The water in the cloth helps to smooth those edges a bit and level things out. Plus the wet cloth first step is much less messy than the last step which is sanding. Here is the first coat starting to dry:

And after sanding and a quick coat of ceiling white to see how things look:

The top right corner is where the upper valance will tie into the backdrop which will bring that corner more in line with everything else. After that a coat of Behr Charismatic Sky blue was rolled onto the backdrop and I started flushing out the curved parts of the benchwork:

To get the curved front fascia spacing right, I take a 6-8 foot length of 8-10″ tall hardboard and clamp it up to the outside to simulate the lower valance and see where the hardboard wants to naturally curve. Here I’ve got some clamped up so I could trace the curve on some 3/4″ plywood valance support where the trains will pass under the layout:

After the benchwork tweaks I wanted to start plotting out curves for the roadbed. So I got out another masonite strip and some nails to see how curves and easements would look. This is looking north from Sullivan’s Curve up towards CP Walker:

I’m using a 1/4 MDF material for the road bed. This material is resistant to expansion, passed a water soaking test I did (meaning it won’t fall apart when soaked with ballast) and is easy to work with. I’m using a combination of risers and foam under this since there are so many complex landforms which will further support the roadbed. Once I was happy with the way the curves looked, I marked the center lines.  Next I cut the roadbed for Sullivan’s Curve as I needed to start working on the grades down and into the turnaround loop. At this point nothing is attached yet:

And here is the initial look at the transition down into the turnaround loop or staging:

Next I measured out the largest loop I could fit between the two support beams and cut the turnaround loop main board, leaving the center open so I can get underneath to grab anything that may be an issue. This was roughly a 17.5 inch curve in the end which should be fine for N scale equipment. I also plan to install a re-railer under here as well to help minimize issues. I used the laser level to make sure the board was nice and flat:

And from the bottom:

With that piece in place, I need to cut the transition boards to mate up with the roadbed leading out to Sullivan’s Curve. Lots of measuring, fitting and cutting here to get it nice and flush:

Next came the roadbed on the north end of the layout:

I initially clamp the roadbed in place to see how it looks. After making trim adjustments, everything is glued in place and cork profiles where glued into place:

At Sullivan’s Curve:

And down into the turnaround/staging tracks:

Next update is to put track down, wire it up and make some test runs. Thanks for reading!

Cajon Pass Table of Contents Cajon Pass Project Part 3