Section 12 - Tunnel 1 - Part 1

Its time to layout the Section 12 - Tunnel 1 section. The layout design given and druthers of this section is indentified in Station 12 - Tunnel 1.

Design Elements

Tunnel 1 is the lower reach of the Polson Canyon river valley. The right of way tunnels through the ridge line paralleling the Satsop River and approaches the Olympic Peninsula Logging Company sawmill.

This Section consist of one section and consists of  layout design elements (from geographic north to south):

1. A single track main line from Polson Canyon to Sawmill.
2. A single track tunnel. 
   
3. An abandoned OPLC logging line crossing the WWSL main line.
   
4. A turnout off the WWSL main line to the OPLC main line and industry complex.
5. A 90 foot turntable in support of the Sawmill operations.

Section Construction

This section is a turnback curve portion of the WWSL layout. It is approximately 5 foot wide by 4 foot in depth.  It follows standard section construction, except it has three 1x3 girders The two ends of the section are cut out to permit attachment of the module electrical connectors and section interface bolts. See the WWSL section construction reference page for the construction technique.

ROW Design Considerations 

The most critical design considerations on this section is curvature of the main line. The turnback curve section width is 60 inches. Technical specification is a minimum 4 inches between track and the edge of the fascia. This restricts the turnback curve to 48 inches (24 inch radius).

2. Curved track within a tunnel is generally rare in the prototype. It is more common in railroad modeling layout design. The location of the tunnel and the restrictive view minimizes the suggestion of a curve within the tunnel.

Laying out Right of Way

I am not going to go into great detail about putting down the roadbed lines. See the Right of Way Reference Page  for the details if you haven't had the fun to do it before. 

Essentially you're going to follow this process: 

1. Lay out the main line curves. It is a simple 24 inch turnback curve.
   
2. Lay out the tunnel template.
3. Lay out the north and south tunnel portals. 
4. Layout the northern switch to the OPLC main line and sawmill complex. 
5. Layout the turntable approach track from the sawmill yard and spurs.
6. Generally locate the turntable location. 

Because this section ties into both the Section 11 - Sawmill and the Section 13 - Polson Canyon, some layout of those sections will need to be done at the same time, primarily the main line locator at the southern-most Polson Canyon curve (xx inches from the fascia ) and the WWSL and OPLC main lines at Sawmill  (xx inches from the fascia).

Laying out the Turnout

A turnout is required to connect the WWSL main line with the OPLC main line and sawmill industry complex.

Laying the track.  Tunnel 1 Roadway is WWSL Medium Profile Roadway. See 4.2.11.2  Modeling Technique for Medium Profile Roadway for details. See 4.2.3 Straight Track and 4.2.4 Curves for construction details.

Laying out the Structures 

North Portal

North Portal

The North Portal will be a re-creation of the Homestake Pass MT, west portal, NP Tunnel #5. I will represent the latter with a timber portal and a rock shed that extends from the portal. See 4.1.10c for construction details. 

 

 

 

 

Tunnel Bore

The tunnel itself will be a rock tunnel lining upgraded with gunnite coating.Dark gray paint will complete the illusion.The fascia will be removable to allow viewing of the interior. See 4.1.10b for construction details.

Southern Portal  

South Portal

The south tunnel entrance will be a re-creation of the April 2002 Mainline Modeler cover photo.  

The rock wall will be constructed with vertical 2 inch styrofoam insulation with a rock casting overlay.

I will represent the latter with a concrete portal. See 4.1.10a for construction details.

 

 

 

In the next blog (Section 12 - Tunnel 1 - Part 2) I will discuss the Landform Design Considerations.