Kieth,
According to the Rogers Pass Improvement Project the longest tunnel in
Canada and North America has the following dimensions: At the center the
portal
measures 25 feet 10 inches above the tops of the rails and is 17 feet wide.
The drawings showed a curved topped tunnel but the portal is rectangular.
Older tunnels had their tracks lowered. Other portals had notches cut into
the portals to clear double stacks.
I used a file that was 15/16 inch to cut the notches in my N scale tunnels.
I just measured a double stack train height from the rail head and it was a
hair less than 22.25 feet high. No matter what scale you are modeling you
need to check a double stack train height of several cars from the rails and
from the base of the roadbed to make sure you have sufficient clearance.
Curved approaches to tunnels will require at least 2 feet extra height
clearance.
The model portal might have to be taller scale wise than the prototype.
Having had several thousand people visit my layout over the years, no one has
ever noticed that some of my portals were a scale foot higher than prototype
to clear double stacks.
Best Regards,
Rick Spano
_www.scenicedandundecided.net_ (http://www.scenicedandundecided.net)
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