Toy train operating and collecting

So it's been a while since I posted anything on my viaduct project.  For those of you unfamiliar with the history of this, you can read it in these earlier threads:

Anyway, the last I posted was that I had glued the skins on the "problem" curve and on the 40" straight.  I still had the 2 30" straights to do, plus I needed to cut out the arches for the remaining curve.  Here're two shots of one of the 30" platforms being glued:

Since the arches for the remaining curve were going to essentially be one half of an ellipse, I decided to see if I could find a way to trace it properly.  I did, using the method shown at the following link:

Drawing an Ellipse with a Piece of String

I got a length of wood, calculated what the foci should be for the size of the arch I wanted, put in screws at those points, then measured and tied the string to use to draw the arch.  I also had to actually re-learn how to tie the slipknots for the string, so I found this on the web:

Here's a picture of the actual work being done, with the jig that I constructed.  My able assistant Tyler is the one holding the pencil while I snapped these pictures:

You can see where I traced the inside of the curved platform so that I got the positioning right.

Once I was able to trace the arches, I carefully cut them out with my jigsaw.  Well, I traced and cut out the inner skin, then immediately started gluing it to the platform.  After that was done I cut out the outer skin, so, unfortunately I didn't get a picture of both of them together.

Anyway, here's a few pictures of the final step of gluing the inner skin:

With the inner skin glued and trimmed, I took a picture of the preparations for gluing the outer skin:

Here's an image of the next to final step of gluing the skin:

And here are two pictures of the last step:

The next step on this, once I retrieve them from Linda's display, is to cut out and add on the under arches.  That's gonna be a trick.  I'm not sure how to do it, but I'm thinking about adding in support braces glued to each skin, set back from the edge by the thickness of whatever material I use.  As for material, I may try to use the masonite for those under arches that are a true arch, and poster board for those that are not.  Or possibly poster board for all of them.

Oh, here's a picture of them being used in Linda's Halloween display:

Looking Good !

This might seem a bit off-da-wall but what about using expanding foam to fill in the arches ? After it cures rough cut excess with a coping saw then fine tune the cut with a hot knife. A skim coat of plaster or joint compund to fill air bubbles then prime. Believe Krylon puts out a series of paints that when dry look like stone, concrete, etc.

 Really looking great !!  This is really a great thread, it should be saved somewhere, or sent to CTT for publication!

Great looking work.Please keep posting pics of your progress.

Hey, that brings back memories.  Looking good.

Now, take a trip to the floor store.  They ship vinyl rolls in hard cardboard tubes.  This is what I used for my arch linings.  You'll make a cut down the center.  Turn your viaduct over, peel the tube open, rough it across each arch, and mark the interior.  The cardboard tube may "shell" but you are only worried about the interior of the material anyhow.

nice job and thanks for sharing your neat construction techniques

DJ, Dude, that is pretty cool! I like the idea of the expanding foam to fill in the arches. The set up looks great. Excellent thread!
Bob.