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Tunnel project
https://bigindoortrains.com/forums/viewtopic.php?f=19&t=324		 Page 1 of 1
Author:  winced36 [ Sun Oct 23, 2022 9:51 am ]
Post subject:  Tunnel project
After building the castle/tunnel project, I started kicking around an idea for a second one. Two years later, I'm finally getting to it. Since it's underpinnings are wood, I decided to put it in the wood structures sub-topic. Cardboard and papier-mâché will comprise the covering.

This one is on a curve designed to accommodate 27-inch diameter track, i.e. O-27 gauge which, coincidentally, is the same radius as the Marklin two-rail clockwork track I have. The dimensions are approximately 20" square.

Assembled the basic structure from scraps found in the shop:

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The base is cut from a couple pieces of 1/4-inch plywood, the tunnel supports from scraps of 1x6 white pine. The plan in my head requires an access hole to the interior, so I cut that in the inside section. The tunnel lining is USPS priority mail packing box corrugated (probably the best corrugated cardboard I've found for strength and dimensions). This time of year I receive a lot of stuff in USPS packing boxes and I save them all. Good stuff.
Author:  winced36 [ Sun Oct 23, 2022 10:20 am ]
Post subject:  Re: Tunnel project
The first pass was assembled exclusively with Titebond glue, but in this next step, I went back and added a few exterior-grade wood screws to tighten everything up. I needed to make a strong column in the center of the base, so I cut that from a bunch of scraps, than stacked them up like a giant sandwich. More Titebond, then clamped for a few hours, we got that installed. Next, I cut a top from a piece of furniture-grade 3/4-inch birch plywood. I cut a couple holes, than mounted it on top of the tunnel supports, the 3" x 3" column, and a small support I cut for the opposite side. Now it's nice and sturdy across the center:

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A few more wood screws and I think I could stand on this. That should be unnecessary, but at least if I should drop it, the interior structure shouldn't come apart.

I tend to be a stream-of-consciousness type builder, i.e. no planning other than a hazy idea in my head, and now came my first problem. The project required access for a power cord, but I hadn't thought too much about that. I had figured on just running it out through the access hole and out from under the base, but of course that would propped the base up slightly and was rather unsightly. The solution was to cut a small slot in the 1/4-inch base and cover it with a small piece of scrap plywood.

Another problem is that when I screwed everything together, the base warped slightly (maybe an 1/8-inch). It won't matter I don't think, but it's not perfect, for sure. We're moving on.
Author:  winced36 [ Sun Oct 23, 2022 10:30 am ]
Post subject:  Re: Tunnel project
This past week I started building the topographic partitions that will form the "mountain" that the tunnel passes through. I used much the same technique I used when building the castle/tunnel project - simple corrugated partitions cut into random profiles. The important thing was to soften/transition the edge of the top so it didn't look like the big flat surface that it was. To do that, I added a bit of hill-top along the edge:

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A problem I ran into with the castle/tunnel project was the ribbing of the partitions in the covering. In some places I found it to be unsatisfactory, so I'm going to put some webbing between the partitions to try to mitigate that. That's the next step.
Author:  winced36 [ Sun Oct 23, 2022 11:00 am ]
Post subject:  Re: Tunnel project
So once all of the partitions were glued in place, the process of adding some webbing could begin. I used a mixture of some light cardstock and a few sheets of plain computer paper, cut into strips that varied from 3/16" wide to 1/4" wide. Basically, I just cut strips and cemented them across the partitions using a mixture of Titebond and some Elmers white-glue:

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The process was to glue one end of each strip in place, than go back ten or fifteen minutes later and glue the opposite end in place. The Titebond works well because it's a bit tacky and the strips would hold in position until you came back and glued in the opposite end.

The transition from the hillside into the tunnel portal is tricky. The portals on the castle/tunnel project was simpler, as they jutted out slightly from the hillside and the papier-mâché could just run up to the edge. Here the portals are recessed slightly into the hillside, so I needed to fashion some webbing that would help support the transition. I glued one end of the webbing directly to the face of the portal, than the other end around the adjacent partition. Hopefully this method works. It's going to be a bit cramped.

Another thing I needed to address was a couple of "terraces" I wanted to include in the hillside to accommodate a pair of structures. This idea came from Lionel's prewar 916 tunnel that featured small buildings on the face of the hillside, the windows of which were illuminated by a single interior light. I wanted to try to replicate that feature here, but with a couple of buildings a bit larger. The question is how to do it. I added a base for each, but I need to think a bit more on the building construction and their placement into the hillside.

More when I get an idea.
Author:  winced36 [ Thu Oct 27, 2022 12:22 pm ]
Post subject:  Re: Tunnel project
After a bit of debate, I went ahead and glued in a couple of glitterhouse-style building shells. I realized that since these would be built into the hillside, I needed to have the basic structure in place before papering:

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Once that was done and a few more bits of webbing added, I could paper it. I spent last night tearing up grocery bags into small bits, then this morning I mixed up the usual two parts white glue/one part water recipe. This tends to be a back-breaking task, but finished in less than two hours:

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So now it needs to cure for a day or two, than a bit of touch-up. I have some painters caulk around here somewhere; I might try that for filling seams and holes. Then we'll start the painting process.
Author:  winced36 [ Sat Oct 29, 2022 11:58 am ]
Post subject:  Re: Tunnel project
There was a bit of unexpected shrinkage of the papier-mâché in a few spots, so some repairs required this AM. Otherwise, things look relatively good and strong. Another day for these spots to dry out, then painting can begin.

Looking it over, the carboard rib structure is still apparent. All that effort at webbing over the structure didn't seem to help much.
Author:  winced36 [ Tue Nov 01, 2022 5:29 am ]
Post subject:  Re: Tunnel project
A bit of work on the tunnel portals over the last couple days:

Image

This is basically a repeat of Howard Lamey's methods as executed on his original castle project (bits of thin corrugated cut, bent, and mounted on rough-cut wooden portal). IMHO, this achieves an excellent "tinplate" appearance that can be finished using any of a number of options.

A bit more patching of the papered shell also completed, so we're getting close to starting the painting process.
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