Sunday, November 5, 2017

TUNNEL PREPARATION

One of my goals over the past summer and now into fall, has been to move toward scenery rough-in.  As I started down this path, I quickly realized I needed to prepare for the tunnels on my railroad.  My layout features ten of the prototype’s twenty tunnels from Oakridge up to Cascade Summit.  Even down at Oakridge, there is an important tunnel through the ridge separating Westfir and Oakridge.  As seen in the past several posts, I have been working actively in the Westfir area.  I would like to flesh this out a bit more with Tunnel 22 and the ridge.  After that, there is a steady progression of tunnels up the mountain grade.

Key elements needed to be in place for the tunnels include supports at roadbed level around the portals and initial tunnel liner, tunnel portals, and the initial tunnel liner.  This past summer, I installed the roadbed supports (bracketing the spline roadbed) and placed mock-up tunnel portals.  The portals were cut from plywood and placed to check geometry.  The mock-ups have been in place for a number of operating sessions and have not caused any issues with the most demanding rolling stock on my railroad—long wheel-base locomotives and autoracks.


Tunnel 22 site between Oakridge and Westfir.

Tunnel 22 did not require roadbed extensions, as it already had such a plywood base.  I already had portals for Tunnel 22.  This is the one tunnel on my railroad built during the Harriman era.  As such, I am able to use commercial tunnel portals offered some years ago by M-Tech, a Sacramento-area supplier of various useful models for SP modelers.  These portals are shown in the photo above propped up against the backdrop.  Quite by happen-stance, their geometry matches the portal geometry I designed for the rest of the portals.  I did not investigate these portals until after I had made the initial wave of plywood mock-ups.  They overlay nicely. 


Tunnel 21 site, just RR-East of McCredie Springs on my layout.  I had to place plywood roadbed extensions to provide support for the tunnel portal and liner.

The remaining key item for Tunnel 22 will be the tunnel liner.  In common with the rest of the tunnels on the Cascade Line, the initial bit of tunnel is lined with a cast concrete liner for about the first fifty feet.  The remainder of the tunnel interior is lined with timber that eventually had gunnite (concrete) sprayed on.  I will represent the latter with removable foam-core panels with strip-wood vertical braces representing the original timber construction.  Dark gray paint will complete the illusion.

The cast concrete tunnel liners need a more formal modeling approach.  I have been building plastic masters for molds to make plaster castings for the tunnel liners and a couple of tunnel portal designs.  Additional casting masters are planned for the rock shed portals, portal wing walls and trestle piers.  I chose to cast the tunnel liner as two halves.  This saves mold material and should permit easier removal of the mold from the cast liner.


Tunnel liner master under construction.  The liner is upside down here.


Tunnel liner master inside the mold box.  The liner surface was formed with 0.020-inch thick V-groove siding with 0.080 inch spacing.  Random “boards had 0.010-inch thick “planks” attached to help represent the original concrete formers used for the tunnel.  The trapezoidal box fits onto mold wall shelves to occupy much of the open space above the liner side.

I am using a silicone RTV (Room Temperature Vulcanizing) product from Tap Plastics:
https://www.tapplastics.com/  Tap Plastics website includes instructional videos on the mold making process.  The pair of five minute videos on simple mold making plus mixing the silicone are excellent.  Not noted in the video, though, is just how fast the mixed (two-part) material begins to turn viscous.  It looks like the working time for decent flow of the silicone RTV is about a half hour.  I am watching my initial batch slowly drip from on high (removing air bubbles) and can see I will need to mix a new batch to complete the first mold.  Note to self—make smaller batches. 


Silicone RTV dripping into the tunnel liner mold box.  Tap Plastics recommends dripping the mixed material from a high location to remove bubbles from the silicone.

In my first wave of mold master creation, I built two tunnel portals.  Both represent the cast concrete portals used in the 1926 construction of the SP Cascade Line (Natron Cutoff).  Fortunately, all tunnels on the line were completed in 1926, so those date numerals could be used for all of my concrete portals.  I used  Grandt Line’s “Building Date Plaques and Number Set” (300-5219) for the numerals.  I built the basic shape with various bits of thick styrene sheet and strip.  I bored the hole for the tunnel arch using a 2.5-inch hole saw.  This provides a hole with at least a 1/8-inch margin around the NMRA clearance guage. 


Boring the tunnel arch.  Front and back plates are tack-glued together and clamped.  The 2.5-inch hole saw is chucked into my variable-speed drill run at a low speed to prevent melting the plastic.

The tunnel face used Evergreen V-groove siding, 0.040-inch thick with 0.080-inch spacing, similar to the tunnel liner.  This sized planking is a bit bigger than what I see in photos of the prototype portals, but helps me convey the impression of individual boards used for the concrete forms.  I attached “planks made of 0.010, 0.015, and 0.020-inch thick by 0.080 styrene strip to represent the form planks. 


Basic tunnel portal master under construction.  The thin styrene strips representing concrete form planks will be trimmed.


Tunnel portal mold boxes.  The portal masters are glued to the box base.  Box sides are attached to the base using silicone caulk.  The side walls are also held in by base strips.  The cross-walls are held in place by strips on the ends of the side walls.  

As noted, I have built two tunnel portals.  The first, basic portal will represent about a half dozen of the portals on the line.  The second one has extended walls representing the rest of the portals.  Castings from this master will be trimmed or cut as needed to represent the top-angled walls used in for several of the portals.  I probably could have saved some effort by just making this larger portal master, but I needed to be sure of my construction technique with the basic portal.


Friday, October 20, 2017

WESTERN LUMBER – 2

Continuing development of my version of Western Lumber at Westfir, I added the log chain up from the log pond, the railcar chip loader, and a lumber loading dock.  Each required additional location preparation.   I previously reported construction of several of the major structures for this industry:  https://espeecascades.blogspot.com/2017/08/western-lumber-1.html


Further development of Western Lumber at Westfir shows in this overview.

First up was further work on the main sawmill building. I completed the major roof trusses.  This allowed me to assemble the main roof as a separate unit.  The roof will remain separate so I can add additional details inside the main mill building.  I also completed the extension of the green chain, which lies underneath the open side-shed of the sawmill.  This was a simple splice job, though care had to be taken for splice locations for the mounting pins for both the green chain and tables and the canopy.


Main sawmill building with roof removed.  Major roof trusses provide strength for the walls and the roof assembly.  Note the green chain has been extended out of the side of the mill.

The log chain brings logs up from the log pond, through the de-barker, and into the sawmill.  Using the Walthers kit pieces led to considerable planning, mostly dealing with elevation changes.  The Walthers parts and their support pieces are designed for a relatively flat terrain, with the log pond surface only a ¼ inch lower than the sawmill.  My Westfir scene needed more vertical elevation.  Indeed, my compression of scene elements accentuated the slope down to the main river “plate” under the railroad bridge. 

My solution took a cue from the prototype Westfir scene.  Western Lumber created their log pond by placing a dam across the river.  A major difference for me was my placement of the railroad bridge below the dam rather than the prototype location above the dam.  Still, the river dam provided a way to raise the log pond for both my model and the prototype sawmill.

One more complication was created by my use of plywood as the main sub-base for both the railroad and the industry area.  I needed to create a channel for the log chain to climb from the log pond up to the mill.  I did so with a couple of layers of plywood, creating ¾ inch steps in elevation.  I still needed to create more of a channel, so the pair of stepped plywood “platforms” came out of the layout a couple of times as I refined the scene.  This would have been easier if I used extruded-foam insulation for the scenery elevation change down to the pond.  I intend using the foam for much of my scenery, but I was just not there yet for this scene.  Sigh.  Lots of work with power tools applied to the plywood.


Stepped elevation changes created with plywood for the log chain as it climbs from the log pond to the sawmill.  Visible here is the channel cut out for the log chain and sculpting of the plywood layer edges with a belt sander.

The next item on my installation list was the chip loader for the rail spur.  The chip loader is one of four structures that are part of the Walthers Sawmill Outbuildings (933-3144).   I began by assembling the chip loader pretty much per the Walthers instructions.  That included the orientation of the discharge pipe for chips from the mill and the machinery shed alongside the loader assembly.  I discovered I needed to bring the discharge pipe over the machinery shed, with the shed on the sawmill side of the rail spur.  Out came a second kit (I stock-piled several).  With that orientation corrected, I needed to deal with a serious height issue.  The discharge pipe and hood hung way too low within the overall rack structure in the stock kit.  I found I needed to remove about 2.5 scale feet of the hangers for the hood and trim a similar amount from the bottom of the discharge pipe to allow chip gondolas to roll under the chip loader.  Even with this modification, I needed to place the chip loader assembly onto a thicker mounting pad to provide additional clearance.


Railcar chip loader. The chip hood needed to be raised to clear standard SP chip gondolas.  The assembly has been placed on top of ¼ inch cork, while the track is on 1/8 inch cork roadbed.

The final item added in the current wave of details for Western Lumber was a lumber loading dock to fit under the loading shed.  This was yet another scratch-built loading dock using Evergreen styrene dimensional strip and scribed sheet for the dock.  There are 180 posts under that dock!  Oh yes, the lumber shed was another example of a too-low structure built from a standard Walthers kit.  I needed to mount it on ¼ inch thick cork to raise it above the railcars I need to slip under the canopy.  Eventually, these mounting pads will be blended into the rest of the scene, providing a not-quite-so flat industrial site.


Underside of lumber dock for Western Lumber.

One of my operators asked recently whether I scratch-built anything on my railroad.  The implication of the question dealt with structures.  I responded that I was mostly using kit-bashing to flesh out the railroad right now, but that I reserved my scratch-building efforts for signature structures, such as the (yet to be built) engine shed at Oakridge.  Upon further reflection, I realized that I have been scratch-building all along as I build the layout.  The lumber dock is a good example of the utilitarian structures I have created.  Other examples are the bridge piers and abutments needed for my bridges.  These structures may not be impressive in a conventional building sense, but they are absolutely vital to the railroad.


Western Lumber at Westfir.

Western Lumber and all of the Westfir scene are developing into a photogenic site.  This corner of the layout has been rising on my priority list for scenery treatment.  That awaits future blog posts.