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Hello,

I am constructing a tunnel.  Currently, the opening height is 5.75 inches, which is 1 inch  higher than my tallest engine when sitting on the tracks and bed.

But, to me, the opening looks "too tall."   

Is there a standard opening height in O Gauge for tunnels and for clearance of trains running through underpasses?

By way of example, for O gauge trestle sets, what is the height of the tallest set of trestles?

Thanks for any information.

Mannyrock

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Pictures show the South Portal of the tunnel on my 10'-by-5' O gauge layout. The item is MTH Railking Realtrax O gauge Single Train Tunnel Portal 40-9014. The opening height is 5-11/16 inches (5.6875") and the width is 4-1/4 inches (4.25"). Full 1/48 scale height is 22 feet 9 inches. Full scale width is 17 feet.

MELGAR

MELGAR_2023_1210_77_SOUTH_PORTAL_10X5MELGAR_2023_1210_80_SOUTH_PORTAL_INTERIOR_10X5

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Last edited by MELGAR

Thanks guys for all of this great advice and info!

John, could you please give me the interior width of your tunnel portal, and the overall width of the portal structure?

Melgar, could you please give me the overall width of your portal structure?

Both of these look great, but I am trying to figure out which would fit best against the edge of the layout table.

As with Melgar's portal, mine may have to spill over the edge a bit.

I don't run high cube or similar cars, so I think the height I have is really close to the two you have shown me.

Thanks again,



Mannyrock

@Mannyrock posted:
Melgar, could you please give me the overall width of your portal structure?

As with Melgar's portal, mine may have to spill over the edge a bit.

Mannyrock

@Mannyrock,

The overall width of the MTH portal at the bottom is 7-1/2 inches (7.5"), 30 feet full scale.

My portal is mounted slightly to the outside of the track centerline to provide slightly more clearance for 21-inch Atlas O passenger cars as they come off the curve inside the tunnel. I positioned the portal by testing the actual clearance (outside and inside of the curve) with the car pictured below.

MELGAR

MELGAR_2024_0228_12_CDOT_FAIRFIELD_COUNTY_12X8

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@Mannyrock,

This is the East Portal of my tunnel. The height is 6 inches (24 feet full scale), the opening width is 5 inches (20 feet full scale) and the width at the base is 9 inches (36 feet full scale), The East Portal is larger than the South Portal. I had to use the smaller MTH portal at the south end of the tunnel because the track there is closer to the edge of the table and the larger portal would have overhung the edge by about 3/4 inch - which was too much... I bought this portal from one of the online scenery materials vendors.

MELGAR

MELGAR_2023_1210_79_EAST_PORTAL_INTERIOR_10X5

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Last edited by MELGAR
@MELGAR posted:

@Mannyrock,

This is the East Portal of my tunnel. The height is 6 inches (24 feet full scale), the opening width is 5 inches (20 feet full scale) and the width at the base is 9 inches (36 feet full scale), The East Portal is larger than the South Portal. I had to use the smaller MTH portal at the south end of the tunnel because the track there is closer to the edge of the table and the larger portal would have overhung the edge by about 3/4 inch - which was too much...

MELGAR

MELGAR_2023_1210_79_EAST_PORTAL_INTERIOR_10X5

Like how you have finished the inside!

Ron

For an alternative "cut-rock" inside tunnel effect, do this.

1. Measure the interior wall of the tunnel and cut a piece of heavy-duty aluminum foil to that dimension.

2. Wrap the aluminum foil into a semi-tight ball and then unwrap it so it's flat again.

3. Paint the aluminum foil with a light coat of flat black rattle can paint, so it's 90% covered, but there's still flecks of silver showing through.

4. Glue the foil to the inside of the tunnel wall with your choice of glues (construction adhesive works). You don't have to coat the whole piece - a few dabs of glue in the corners and a few scattered about will do fine.

5. Repeat for the other inside tunnel wall.

When a train with a headlight passes through, it will give the illusion of cut rock inside with specs of silvery minerals shining through. 

Fantastic information from all.

The side walls of the outside of the tunnel are currently vertical walls of exterior grade plywood.  Any ideas about how to make these look like sheer walls of a stone cliff?    I can't make them stick out too much further in thickness, or I will be crowding the side of another track.

I have zero experience with this.  I know about the modeling "cement" I have read about. But, how to make it stick to a vertical plywood surface?   Perhaps nail on a sheet of welded wire with 1/4" x 1/4" squares, and use this as an underlying "lattice" to hold the cement?

Mannyrock

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