Building bridges using mirrors

A highway overpass makes an ideal candidate to disguise a dead-end on your model railway. Adding a few mirrors beneath your bridge however will trick most eyes into thinking that your railway line actually continues through some imaginary portal.

The modern highway overpass supports are made from balsa, and were carved using a sharp hobby knife.

When I first began building my HO scale bookshelf model railway, I took into consideration the need to disguise the sudden end of rails at each end of my layout. In my earlier post adding theatre stage effects, I explained how I added the mirrors to my layout ends for less than six dollars, but now that my layout is progressing further, it was time to actually disguise the mirrors. And to do so, I made a modern highway overpass from balsa wood. The height of the bridge was predetermined by the height of the small mirror panels I had used, in this case, 80 mm high mosaic glass panels that were glued onto my sunken mouse-hole door. The bridge actually stands 67 mm above rail height. I started by cutting 2 pieces 72 mm tall x 15 mm wide at the top and 40 mm wide at the base from 5 mm thick balsa wood, and carved concrete block joins in alternating patterns of 15 mm tall x 10 mm wide blocks.

After test fitting the highway overpass supports, I then built the adjoining terrain from polystyrene foam.

After test fitting the highway supports, I next shaped the adjoining terrain using the same method I explained in my previous post modelling using polystyrene foam. Finally, I measured the width across the book-end of my layout and made the concrete highway structure again using 5 mm thick balsa wood for the base, and glued a 12 mm strip of 3 mm balsa for the side safety barriers. Using a thin strip to simulate the highway creates a 3-D effect for what is essentially a fake road overpass glued against a blue backdrop.

I then stained the concrete join lines on the highway overpass supports...

Next I stained the carved join lines of the overpass supports using nothing but the dirty black water I had my paint brushes soaking in, although using India ink would probably give a better end result.

...and then painted each individual square in different shades of grey, along with the narrow lip of the highway overpass.

I painted the highway overpass support pylons using water based artists acrylic while leaving the darker join lines showing. Each square was given several thinned-down coats in different shades of grey to try and replicate the same pattern effect I see on most modern Australian highway overpasses. The shallow highway relief was painted in a dark black-grey and the safety barrier edging in a light buff grey to provide a simple yet effective contrast.

The end result is a shallow relief highway overpass that doesn't take up too much room on my layout.

Finally I glued the sections of the highway overpass into place using a water based PVA wood glue. As I explained in my modelling using polystyrene foam article, any solvent based glue will simply dissolve the foam right before your eyes.

To conceal the space between the mouse hole door of my layout, I added the extra strip of detail as shown.

Those who remember the early stages of Philden's construction will no doubt be making the association at this point with my mouse-hole door. The beauty of this highway overpass is that it also conceals the only entry and exit point on my bookshelf layout, via a hidden mouse hole, that will later lead to a removable staging yard. When the door is closed, viewers only see the mirrors beneath the bridge. When the door is open however, the space beneath the bridge becomes a portal to the rest of the New South Wales Railway system.

No, its not 2 wagons but 1. Its a cheap trick to fool viewers into thinking the line continues beneath the bridge.

While this was a simple enough project, its execution is critical given that the mirrors will reflect everything that is hard up against it, including any mistakes. While pleased with the end result, the one thing that did not occur to me until taking the photographs was that the alternating pattern of concrete blocks on the highway supports are repeated on the last strip that ends hard against the mirror. And I still can't figure out how I could have avoided this! Anyway, maybe once the scenery is in place along with some overhanging trees, maybe no-one will notice but me. But as usual, that's a story for another day.

See also; Detailing a Highway Overpass and Adding theatre stage effects