Tuesday, November 28, 2017

TUNNEL PREPARATION – 3 -- MORE PARTS

Preparing for the scenic effect of tunnels on my SP Cascade Line involves many steps.  The previous pair of posts described major pieces needed for each tunnel—tunnel portals and the initial tunnel liners.  https://espeecascades.blogspot.com/2017/11/tunnel-preparation.html

As I went into production casting tunnel liners (forty halves needed!), I continued creating additional casting masters needed for the tunnel entrances.  Specifically, I needed wing walls—triangular retaining walls alongside the portals—and another portal for the rock shed galleries that lead into a number of the tunnels on the Cascade Line. 


Tunnel wing wall masters.  The rear (left) wall needs to have the form board strips trimmed.


Wing wall mold box.  I intended mounting the two wing walls in a more compact mold box with the two triangles nearly forming a square.  Convention overcame me when I placed the walls on the mold base plate.  I mounted them as mirror images.  That led to the diagonal mold box walls at the top.

I used the same technique for representing form boards on the wing walls as I used on the two main portals previously described.  Various thin thicknesses of Evergreen styrene strip overlaid scribed sheeting which provided a horizontal line reference.  As with the wide wall portal, the wing walls can be cut down to whatever size or angle is needed for a specific installation.

The Cascade Line had a number of open gallery rock and snow sheds leading to the tunnel portals at higher elevations.  See Tunnel Nine’s East Portal: http://spcascades.railfan.net/TUNNEL9.html
And the photo below:


Rock and snow shed at RR-West portal of Tunnel 5.  A. de Gues photo.

The sheds were cast in concrete.  I will build my gallery sheds using styrene tubing for the pillars and hardboard sheet for the roofs and back walls.  The tall and relatively thin pillars do not lend themselves to easy plaster casting.  The gallery shed portals need to be a common design with the “1926” date casting.  I built a portal master using the same 5/16 inch tubing that I will use for the pillars.  I will hope for the best when pulling these out of their molds, though a break can be repaired with glue. 


Rock and snow shed portal master.


I just got a new bag of US Gypsum Ultracal 30, so I can cast these parts plus the regular tunnel portals and tunnel liner halves in quantity.

1 comment:

  1. Bill,

    I've read through all of the recent posts on building the tunnel portals and liners, along with the molds. Great stuff! The idea of using Evergreen styrene strip to get the cast lines in the concrete is brilliant! And the finished products really turned out well. Having the prototype portals and liners on the railroad will certainly add a level of realism that is not often seen. Nice work!

    Tom Patterson

    ReplyDelete