How have you made tunnel liners? - Trains.com Forums

hi Ron

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I made mine from thin foam board and painted with woodland tunnel black. the paints doesn’t reflect light and is very convincing.

pro

cheap and easy to make.

bends around corners

cons

no detail to show cutting, that said with tunnel black most detail would be lost.

chris

My tunnel liners are intended to look like rock. Only the sides are lined and I made them high enough so you can not see the tops of the liners. They are plaster castings I made. The process was to make a wood frame to hold the mold. The mold is crumpled aluminum foil which is pread into the woord frame. Then I filled the molds with plaster of Paris. To go around the curve, I have a series of straight sections. I used watered down acrylic paints with vaious colors. It was not neccessary to go very deep in the tunnel because of darkness.

How elaborate you get depends on what you are doing.

LION builds subways. Lotsa tunnels, and always needs more tunnel walls. Fortunately subway tunnel walls are mostly concrete. LION models most of these with foam or Homasote, but has recently taken to using just plain old corrugated cardboard. Paint it black, apply some latex caulk to the bottom and drop it in place. They do need covers on them!

But what if you use a “Rail-Fan Camera” Your tunnels will need much more work on them.

But what if you want to access the tunnels to get the 0-5-0 switcher in there? Walls and sides get in the way. LION is considering using removable walls. Install them for a photo shoot, take them down so viewers can see what is going on.

Here are two videos of my layout. Let me know what you think of the tunnels.

ROAR:

http://youtu.be/hnr82S3MZ8Q

http://youtu.be/wtxsd_wqv

LION has added much since this last video was taken, mostly because him looked at it and liked not what he saw. More tunnels and stations are in place now, but of course it is no where near finished yet. Maybe him will shoot another video tomorrow so that we may display the progress.

For more information, please visit Tunnell Lliner.

ROAR

A timely thread for me as I’m just now deciding what to use. I’m so far, settling on one wall (only) of black painted tin foil for a hard to reach corner where only that wall can be viewed. It’s on a very short (two-three cars) interchange so no flatcar riding cameras will ever go in there.

I’m using Bragdon Geodesic Foam for my mountains so I will make all fully visible tunnel liners with that material. Just take a fresh/uncured casting and drape it over my forearm and voila! a true rock tunnel liner.

The one walled tin foil liner will also be easy to “bat” aside should I ever derail and need to insert a grabber tool in there to retrieve anything. It will also be easy to replace should it get damaged by putting glue on the bottom and placing it inside the tunnel with the same grabber tool.

Only one short tunnel, about 450’ long, on my layout (they weren’t very common in southern Ontario) and it’s over a mostly-curved section of track on a 2.5% grade

Here’s a train exiting the upper portal:

…and, on another occasion, a train emerging from the lower one:

In the second photo, you can see daylight in the tunnel, visible only because the mountain over it hasn’t yet been completed.
Here’s a behind-the-scenes look, with the lower portal visible in the distance beneath the unfinished scenery:

The tunnel liner, used only immediately inside both portals, is a piece of black construction paper, formed into an upsidedown “U” and stapled to the edges of the 3/4" plywood subroadbed. The entire length of the tunnel track has a low “fence” of 1/8" Masonite fastened to both sides of the subroadbed, in case of derailments, and the track is accessible from below. Once the mountain is closed-in, there should be no light visible inside the tunnel.

Wayne

I made the portal, retaining wall and liner from styrofoam, that were cut to shape and glued together (I used acrylic latex caulk to glue them together). I hand carved the rocks that the portal and retaining wall. I, then glued the portal to the subroadbed. I made sure to check clearance as I shaped the liner. Once, I had the necessary clearance, I covered the inside walls with a layer of plaster, texturing it as I went. I painted the interior using acrylic based paint. Here’s where an airbrush comes in handy, so I could make a gradual transition from dark earth based color to black. The liner is only about 8" deep because, The mountain keeps it dark inside. The top of the mountain is removable and there is access from the backside of it; things DO happen inside mountains! [banghead]

I’ve also built subways. One of my lead cars has a video camera in it, so I wanted to line the tunnel walls so that there would be a tunnel wall to see all through the tunnels.

I took a clue from the textured ceiling of my train room, literally. I made wall sections from styrene, and then mixed up some Hydrocal, quite thin, and rolled it on with a paint roller. Once it was set, I sprayed with gray primer and misted on a bit of black.

The styrene easily curves around the 18-inch radius walls. I used the light gray color to “brighten up” the tunnel for the video camera. You can see a LED on the left (inner curve) wall. I added lighting, too, but placed it on the inside of the curve where the camera couldn’t see it.

Another technique I’ve seen here is to make a loop of heavy wire, #12 I believe, and connect the ends to the business end of a Weller soldering gun. This provides a stiff “hot wire cutter” that will hold its shape. The modeler used this to cut his tunnel through stacked pink foam.

At Boothbay Railway Village, we have been working on a number of tunnels.

We started casting liners in Hydrocal using the WS tunnel liner form. These make a nice “blasted rock” liner, and can be configured to make single track or double track liners. They work great of straight sections, but have to be cut to fit curves. Also, if you have a narrow space with other structure in the way, they are difficult to fit. The liner mold is a thin blow molded plastic and becomes fragile after a few years. Casting is a slow process, if you need a lot of liner pieces, you probably should get multiple molds. We have 6 of them.
http://www.walthers.com/exec/productinfo/785-

Lately, we have been making liners from 1’ extruded foam insluation board (blue or pink foam). We make an opening slightly larger than the tunnel portal, and laminate pieces together to make a liner to the appropriate length. Sawing or cutting the opening leaves a rough surface that looks like blasted rock. For curves, foam board can be offset and glued together to fit the curve, the sawtooth apearance inside a can be smothed using a file or Surform tool. We paint the inside with a flat black paint. If a further view block is needed after 6 or 8 inces, we line the edges of the track with 1/4" black foam board leaving the top open. Styrofoam is messy to work with - lots of small pieces that stick everywhere, static cling, but a lot easier to work with than plaster. The foam liner can be easily mofified to fit tight clearances.

If you are looking for more details, kindly visit Corrugated Steel Culvert Pipe.

I am designing the final lining for construction under a lake. In operation the tunnel will be full of water. My controlling case will be during the construction period the lining will support the hydrostatic load. The head has been determined from the flood level of the lake. The liner should be unreinforced concrete and the tunnel is in rock.
To this point I have used the .55 strength reduction factor (ACI318 9.3.5) and I applied a 1.6 load factor to the hydrostatic pressure. The load factor is 1.6 rather than 1.4 because there is not a control of the flood level. The construction period is over 1 year.

Am I being to conservative?
I am not at all experienced in the design of tunnel liners, so please keep that in mind as you read my post.

Using a strength reduction factor of 0.55 and a load factor of 1.6 equates to a factor of safety of 2.9, which is high for temporary works.

An approach that is used in cofferdam design is to set a design flood elevation and only allow work in the cofferdam when the water surface is below this elevation. If it goes higher, vents (cut-outs) are used to flood the temporary works automatically so as not to fail the cofferdam.

You could design for a 2-year, 5-year, or 10-year storm and cleary note this on the plans. If the water level exceeded this level, the tunnel might have to be flooded until the water level receded.

With this approach you should be able to use the lower load factor as the unknowns would already fe factored into the design.