Single Track Tunnel Portals and Installation on Curves

I also learned this lesson.

Boy does your experience hit home, Brian!  I put two individual single tunnel portals side by side  -- one set back a little bit on the curve from the other -- on 0-72 curves and was surprised to see how many cars either rubbed the tunnel side or wouldn't fit at all. Inter modals, 60' boxcars, things like that.  A lot of them gave me trouble on my inner loop.  Unfortunately I discovered this only after all the hillside, ground cover and landscaping were in place.  The only way out was to "make room" with one of these!

At least you were smart enough to make a test pass!!   

- Mike

Very good advise Brian. I have a double track portal on my subway line using 036 curves and it is close with my Rail King subways. I dare not try any trains that are longer.

Oh Yeah, that's an issue I've  dealt with with on every display I've built. I don't know how design a track with a portal on a straight section and have no direct experience that would confirm it's even possible.

Something I'm sure you're aware of but others may be interested to know is you should also check (especially with steam Loco's)  reversing back through the portals; the clearance is not the same forward as it is backward.

Make sure to test that your conductor hanging out of the coach doesn't hit the portal.

we like to send engines with sharpened elephant ears around a new line for the first time

I'll second -- third -- uh, fourth that!   Sound advice.

I learned that lesson the hard way too on my first layout. I know better now. Excellent advice! 

We hit that issue early on in the layout build. The way we worked around it was to make 1 1/2 track portals from cut-down 2-track portals. We used the poured concrete style instead of stone as it was easier to re-shape the arch using Bondo. At the same time, we also grafted on height extensions so that they had 7" center clearance to compensate for electrics running with the pans up. When I get back to Los Angeles, I'll check to see if we made a mold of the finished portals.

Similar experience here only it involves a through bridge.  With curves commencing immediately after the bridge, upon entering or exiting longer cars and engines just touch the piers.  Modifying the bridge to fit is too complicated so length restrictions are enforced.

Bruce

I have used a few single portal ones but used a bandsaw with a fine blade to cut the portal wider.  Curves can really mess you up there!

Similar bridge situation happened to me.  I discovered that a single track, O-72 curved truss bridge doesn't necessarily handle large engines rated for O-31.  Lesson learned... Make tunnels and bridges wider on curves!

-Dustin 

been there done that too

Excellent point and advise Brian.  There was an article in one of the train magazines some years ago which explained placing the car or locomotive with the widest overhang on the curve where tunnel portal was going to be located.  Mark the spot of overhang on layout and measure out 1/2" to 3/4" from that mark which indicates inside wall of where portal should be placed.  On my Texas layout I had to cut and glue a double track portal to make it the right size. 

Steve, Lady and Tex

Great point Brian.  I too had the delema and made my own portal out of green foam and the Tippi foam cutting tool.  Looks and worked great.  Keep up the good work!

We have a number of tunnel portals on curves and we made sure the clearances were okay by testing early in the installation process. In fact we would routinely test clearances on all curves with both a Big Boy AND a 21" passenger car.

Then the unexpected happened. Lionel came out with 24" Autoracks!!

The dremel got quite a workout!

I've used the double track version on my layout just for that reason.

Tunnels on curves are the reason my VL BigBoy won't make it around our club layout!

Thanks for all of your replies. When I tell you the engine and cars JUST make it through without rubbing, I am not kidding. Elizabeth was a big help as she did the final fine tuning of the portal locations.

They do look cool, even on the 0-72 curves.

Excellent advice.  IIRC, PTC has a conductor with lantern on the platform of the observation car.

"Make sure to test that your conductor hanging out of the coach doesn't hit the portal."

Never thought of this. I will check it tomorrow for sure.

I had the same issue with a bridge.  I had to modify the bridge so the Big Boy would clear the side coming out of the approach curve.  All is well now.