Thursday 13 February 2014


In the previous post I described the adventure of the field work to record the features of the Tunnel Section of my layout.  Today we will look a little closer at the tunnel portals.  In a future post I will describe a few details of their construction.

Mileage 19.7  The West Portal of prototype Tunnel No. 1 is a bit worse for wear but still intact if the CPR would like to reopen the line!  A few scratches but still serviceable? -  maybe not.  They would have to muck out a fair amount of rock and gravel as the interior has completely collapsed.  The rock shed part of the portal extends 45 feet into the mountain as noted on the plans which the  Engineering Department of CPRail graciously allowed me to acquire from their extensive plan room back in the 1990's (now closed).

Evidently, all the portals and rocksheds of the Coquihalla were originally constructed of Wood Timbers but the CPR upgraded them to concrete in the 40's and 50's.  Even so, the interiors of the tunnels were often lined with 12" x 12" timbers called Tunnel Sets.   According to Joe Smuin's Kettle Valley Railway Mileboards, the tunnel itself was 218 feet long when the west portal was built in 1947.  The east portal was rebuilt in concrete in 1951.

Here is the model, the "concrete" looking fairly fresh as it would be only 2 years old in 1949, my target year for the layout.  By the time that I acquired the official CPR drawings, I had already built the portals from field measurements out of Hydrocal plaster. This ideal modeling medium was poured into a wood form to create the replica in 1:87 scale.

From the plans, I learned that the prototype tunnel was constructed on a 200 foot spiral to an eight degree curve but I had guessed wrongly that the track alignment was still fully curving as it left the portal.  I am glad that I proceeded with this engineering "inexactitude" as it turned out, because I think the scene actually looks better with a curve as can be seen in a photo of the previous post.  Besides, as zealous as I am for prototype modeling, it is too much to rebuild for what is a minor discrepancy.

Mileage 19.9  Now a photo of the East Portal of Tunnel No. 2.  The Prototype:

Both portals of Tunnel 2 were built in 1943 and the total length was 280 feet.  There was a 10 degree curve right as the track entered the east portal ending in a 200 foot spiral as it left the west portal.  Interesting colour in the rock.

And the Model:

That foreground gravel and rock is the real deal, collected from the slopes of mile 19.  However, the caboose is not constructed out of wood and steel from a real one.  Looks like we need a little more colour and some greenery to liven things up.  Plans and field notes should appear in a future post as well as a few details on how they were built.

I invite your comments and questions.  Not sure what the procedure is.  If someone knows, clue me in because I am new at this.

Coquihalla Man

1 comment:

  1. Thanks C. Man, nicely presented re. prototype and your model.
    Am building a helix for the Mountain Division of my H.O. layout
    (loosely based on "Western N. America") connecting both decks
    of the layout with 18" vertical separation. Starting with a circle
    as top loop, each successively lower loop juts out five inches
    more than the one above, all to the same side. A mountain will
    be the finish visible scenery. This allows aisle space on two sides
    and high visibility trackage facing room entrance. Five tunnels
    require ten portals, so I'll be able to model a variety of styles of
    portals and liners. Thanks for sharing your work! Tom K