In this video lesson, modeler Martin Tarnrot demonstrates how he scratch builds tunnel portals for model railroad layouts. Martin uses two inch thick styrofoam to create his portals. Thin styrofoam sheets are also a good alternative if you don’t want to cut the foam yourself. To cut the foam, he uses a styrofoam cutter he made himself to slice quarter inch thick pieces. To remove the fibers from the cut foam, he sands them off using a sanding block with a very light hand.
For the prototype, Martin has found a picture of a tunnel portal. He prints it to scale and cuts it out, ensuring the portal is symmetrical. He then traces the guide on the styrofoam and cuts it using a scalpel and sanding away the burs. Making indents for the stones on the arch with a scalpel following the photo is the next step. Removing the arch will make engraving the surrounding stones easier and will allow Martin to make the arch stand out farther than the surrounding wall.
For the surrounding wall, Martin first engraves all the horizontal rows with a thicker blade and then uses a tool of his own design to make the vertical notches for the individual stones. He cuts out the lower row of stones to be glued back slightly elevated like the arch. To elevate the parts he needs to, Martin uses thin pieces of wood. He goes on to demonstrate how to assemble the walls with SikaBond 530 glue. For more on creating realistic stone walls on your layout or building model railroad tunnels with Allen Keller, visit the Model Railroad Academy archives.