Finally, we get back to new trackage. I'm pretty happy with the potential of the new benchwork configuration, so the plans from here on out, use that configuration as their basis.
Just to the west of Plain siding, we hit the Flatirons portion of the Tunnel District. The Tunnel District itself contains 28 tunnels in 17.1 miles. Tunnels 2 to 29 includes 26 tunnels in about 10 miles, which is one of the highest concentrations of tunnels in America.
Two tunnels are now defunct, Tunnels 9 and 28, and the two tunnels at either end of the tunnel district, Tunnel 1 and Tunnel 30 are both isolated from the rest of the district. The rest of the Tunnel District can be divided into three regions. The first region is Tunnels 2-8, which comprise what I call the Flatirons Region of the Tunnel District. Tunnel 8 is the dividing line between the Flatirons Region and what I call the Middle Region, which extends to Tunnel 18 and Crescent Siding. The Middle Region lies along South Boulder Creek, although for the entire run through this region, the creek lies a considerable distance away from and below the railroad. Beyond Crescent Siding, the Upper Region of the Tunnel District, Tunnels 19-27 and Tunnel 29, lie much closer to South Boulder Creek and even run along the creek itself.
This scene has been similarly captured by Mike Danneman in his layout.
Physically, there is a short separation of single track between Plain siding and Tunnel 2. I wanted to capture that in the plan. Immediately after Tunnel 2, the line sweeps across Bull Gulch on a massive fill. Bull Gulch washed out in October 2013.
After crossing the fill across Bull Gulch, there is a cut through a protruding flatiron slab and then the line enters into Tunnel 3.
Tunnel 3 is often described as a slot through the Flatirons.Tunnel 4 is quite similar, but the west portal emerges from a substantial flatiron formation that leaves much of that portal in shadow. Photos are difficult to come by but some do exist.
So, with all of these iconic images through the Flatirons in mind, I have put together the following track plan that brings the mainline off the second peninsula and along the wall above Leyden Siding.
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| Track Plan for Tunnels 2-5 through the Flatirons. |
So, in this plan, I have a short section of single track between the west end of Plain, and the east portal of Tunnel 2. Tunnel 2 with a length of 31.7", bends around the corner, and the curve continues across the fill of Bull Gulch (over a 33" radius). The mainline cuts through a slab of the flatiron formation, and then the main plunges into Tunnel 3 for another 23.7". These both seem to be long tunnels, but both are proportional to the actual tunnel lengths, as it the spacing between them. Those proportions are continued throughout the Tunnel District. After another brief appearance, the line enters Tunnel 4 for 12.8", appears again along a 21" radius curve (instead of a tangent as in the prototype) before plunging into Tunnel 5 for the next 35.1". Most trains will be continuously playing peek-a-boo during the transit through this part of the layout.
In the plan, I show the tunnel portals, and the width of the tunnel itself. I've hidden the track centerline itself in the plan above. The train continues its climb from Plain (at 26.5") to the west portal of Tunnel 5 (at 29.3"). The entire scene is 17' long, and the resulting grade is about 1.3% which should be enough to be noticeable, but should not be a severe operational impediment. The ruling grade remains out in the open through the Big 10 curves. I think that the scene will be both impressive and immersive in its effect. I am excited about seeing it in reality.
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Cameron Turner
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