Taming the Troublesome Twins
As regular readers have come to know, I don't give up without a good fight, and if I want something badly enough, I find a way to achieve it. In this case, I really wanted to nail the twin tunnel portals—not so much because I insisted on being super-faithful to John Allen's original, but because he'd already solved a tricky modeling problem that didn't have many solutions.
After countless careful measurements, I determined that I could pull it off, but what I needed in order to succeed was considerable control over the divider between the tunnels. And so, as I had for the stone viaduct, I turned to my faithful friend, styrene. The reason it's all so very tricky is that the divider is made up of nothing but angled lines all twisted into a curve. Consider: one track is ascending, one is descending, there's three quarters of an inch in vertical separation between them at the portal, the cribbing faces one side on the top third and the other side on the bottom third. Plus, just to add to the mess, the two tracks follow non-parallel curves. Quite the little nightmare!
Using scribed sheet styrene and square strip styrene, I assembled the tunnel divider (above) one piece at a time, returning to the layout to fit each part as it was cut and bonded to the assembly. Because the curves converge, there reached a point where I could not add any more vertical posts, at which time I considered the task complete.
Almost. After spraying the divider flat black, I temporarily tacked it in place and started running trains past it. This turned out to be a good thing to do, because it highlighted some issues, and I wound up rebuilding the whole thing (much easier than modifying it). Only when the second assembly passed the rolling stock test did I declare victory, and bonded it permanently in place.
Then it was on to the rest of the tunnel construction—which was trivial by comparison—consisting of installing a pair of tunnel liner castings for the walls, followed by black paint and cinder ballast, as per the procedures used for the Daphetid tunnels.
At this point it's all over but the shouting; I have only to make the tunnel portals—such as they are—out of stripwood. When that's done, the last track-related work to complete will be the retaining walls around the branchline switch. And when that's done, watch out—it's time for scenery!