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Tunnel building for beginners?

13K views 34 replies 10 participants last post by  NIMT 
#1 ·
I'm gonna start forming a tunnel pretty soon that will be on a curve. Both sides will be exposed. I've got 5 tunnel portals to start with, 2 for each end, and 1 for the back where the track will split off to a future expansion. I know that you're not supposed to put switches in a tunnel, but I did. I'm gonna try to make a small section close to there removable for access. That will be close to a wall, so if it's not perfect, that's okay.

The issue I'm looking at is making the forms. I'll cut out facings for the portals from 3/4" MDF, what I'm wondering about is what to make the forms out of. Once they're formed, I'll use plaster cloth.

Any suggestions? I've looked a little for youtube video's, but didn't find anything that really covered what I'm doing. Most mountains or tunnels are close to a wall and are only 1 sided.
 
#4 ·
Several options to build a tunnel:

1. Carve out of wedding-cake layers of "pink stuff" foam sheets.

2. Build a "basket weave" form out of strips of heavy corrugated cardboard, then cover with plaster cloth.

3. Build forms out of aluminum window screen.

Sean (NIMT) offered an excellent tutorial on the latter method ... easy, with great results ...

http://www.modeltrainforum.com/showthread.php?t=6374

TJ
 
#5 ·
That tunnel in the post above was just some pink foam formed around the tracks to hide them. I did another couple of tunnels on other layouts here is what I did.











Those were from my first 2 layouts. I dont have any pics of the tunnel from the 3rd layout but it was all done in a similar fashion. If you notice I the first layout there is even a place where the tracks go over the top of the tunnel.

Massey
 
#14 ·
Excellent info here fellas!

I've been watching Massey's thread, the one I had seen on his was situated in a corner, mine will be out in the open.

I've also seen Sean's thread with the screen. That's a great idea, and I'll probably try that, but where his is also in a corner, that brings the question of how to make a mountain, or the best way to make the peak of the mountain?

I'll take a picture later of the area I'm working with, maybe you guys would have a better suggestion.....
 
#17 ·
The reason I didn't go with the stacked foam method was that I wanted the insides of the mountains to be hollow, making it easier to access my trains and wiring that ran through there.

The cardboard strip method is very easy as well.

I think for my new layout I'm going to do cardboard strip for the structure, then use NIMT's screen/drywall mud method to cover. That plaster cloth got expensive.
 
#19 ·
A serrated steak knife works well also.

Have your vacuum cleaner ready - It will work, but you'll make a serious mess with a dremel.

The best way is to get a hot knife or heated wire cutter. Cuts quick and little to no mess.

Keep in mind that you will be putting a thin layer of drywall mud (or similar) over the top of the foam so you don't have to be exact with the shaping of the foam....just kind of close.
 
#22 ·
when building models, having a dremmel around is almost a must have like model glue. I have 2 of them one for normal use and a 75th anaversary model.

Massey
 
#26 ·
I doubt there is a standard dimension for tunnel bores. I think it is going to depend more on the structure of the rock and how much support is needed for the tunnel liner or reinforcement. Some tunnels are not tall enough to permit the transit of double stacks or extra height cars, others can handle it just fine. Some that could not clear double stacks but were in areas that had high traffic levels had the floor lowered to clear the double stacks and other overheight cars.

Massey
 
#27 · (Edited)
jonyb,
Here is a chart for all the clearances.:cool:
Text Diagram Parallel Design Font

So height in HO is 23' X 12 = 276" / 87 = 3.17" off top of rail so 3 1/2" off of the layout surface is a good height
And width in HO is 9' x 12 = 108" / 87 = 1.24" off of center line to side and 2" center to center on straits and 2 1/4" on curves
So 1 1/4" + 1 1/4" = 2 1/2" for a Single tunnel and 1 1/4" + 2" + 1 1/4" = 4 1/2" for a Double tunnel.
This chart is in real dimensions so just multiply dimension in feet x 12 then divide by your scale dimension HO = 1/87.
Hope this helps!
 
#28 ·
Thanks Sean and Massey! I was actually asking the inside width of the Woodland Scenics tunnels, I didn't word that question right. Ive got the single track portals, but the track is too close together to use singles, and (after searching) a little too far apart to use a double track portal. I'm gonna try to move the tracks closer together to see if I can use the double. The opening on it is 4.5, just like Sean said.
 
#29 ·
Here's the area I have to work with. I moved the track on the left hand side of the pic closer together, and it's 4" wide, so I believe a double tunnel portal will work. On the right hand side, it's far enough away to use 2 separate portals. If they were built, they'd be facing where I took the picture from. I think I'll build a wall in teh background to start with.

 
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