Saturday, December 9, 2017

TUNNEL PREPARATION – 4 -- FITTING THE PIECES TOGETHER

“Boring” along on my tunnel project, I have begun fitting the cast pieces together.  As I cast the final tunnel liner half segments, I can see the light at the end of the proverbial tunnel.  Time to assemble the pieces and test.  Previous posts on creating the parts for my tunnels can be found at:

A number of the castings needed to be trimmed to fit the individual tunnel installation.  Most liners needed to be trimmed top to bottom so the portals can stand vertical. The liners are on the 1.8% mountain grade.  I used a hacksaw for the primary cut, followed by sanding with 60-grit sandpaper.

The second liner trimming has been side-to-side to keep the portal square to the track while allowing the liner to angle somewhat.  This was needed for tunnels on curves.  My HO scale 50 feet long liners (about 7 inches actual) are as long as I care to go for a straight segment around my 42-inch radius.  Combined with the generous tunnel width I built into my portal and liner design (about a scale foot extra clearance around an NMRA gauge), my test of long rolling stock through the tunnel liners was successful.


Test of long freight cars through Tunnel 22 leading into Oakridge.  Autoracks on 89 ft. flat cars have the greatest overhang on curves of any of my rolling stock.  Note the offsets between cars for the pair of cars between liners in the middle.

I assembled the liners, portals and wing walls (when needed) using Liquid Nails for Projects.  The assemblies are just placed on the layout as there are several more steps to go.  A critical test will be to have the portals and liners in place for my regular January operating session. 

Herewith a sampling of the tunnel portal installations:



East face of Tunnel 22 joining Westfir to Oakridge.  The M-Tech resin portals have been installed, but the wing walls await a flattening procedure.  Tunnel 22 was built during the true Harriman era on the SP.  Oakridge served as the end of track for over a dozen years while the SP fought a break-up effort by the US Government.


West portal of Tunnel 21 at the entrance to McCredie Springs.  This is the first of the standard tunnel portals from the 1926 construction of the Natron Cutoff—the Cascade Line.


East portal for Tunnel 20.


Tunnel 12.


Tunnel 9 leading into Cruzatte (to the left).


Tunnel 3, the summit tunnel.

This has been a long project to create the tunnel portals and liners and assemble them.  I still need to paint these pieces, but I want to let the casting plaster cure a bit more.  I also need to paint the track and ballast before installing these tunnel ends more permanently. One more operating session will reveal whether adjustments to tunnels or track are needed.


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.