Model train bridges add greatly to the look of a model railroad setup. The bridge gives height to your model, creating an additional layer to your railroad build that aids in immersion and realism. Because of the small size of an HO scale layout, you can build bridges that seemingly stretch across wide chasms, over deep gorges, or crossing over busy city streets in an urban setting. The variety possible with HO scale brides is largely unlimited, but regardless of the design, the basic parts and procedures for building an HO scale model train bridge remain the same.
Measure the distance that you're covering with the bridge and purchase an HO scaled bridge of the appropriate length. Measure the distance from where the bridge will lie to the bottom of the bridged area. Purchase HO scale piers that are long enough to reach to the bottom of the bridged area when evenly spaced along the length of the bridge. Each bridge manufacturer has a recommended number of bridge piers.
Cut the board edges along the bridge route bordering the area you're bridging over. Cut the sides so that the bridge abutment fits snugly against it. The abutment is the concrete or stone model wall piece that sits at the edge of the chasm and supports the ends of the bridge. Sand the edges level with the sandpaper so that you can place the abutment securely against the opening to the covered area.
Glue the abutments in place against the sides of the area to be covered using epoxy glue. Make sure that you place the abutments parallel to one another and that the tops form a level plane to one another. You can check that they are level using a carpenter's level placed across the abutment pieces.
Place the bridge piers evenly spaced along the bottom of the bridged area in line with the abutments. Test the placement of the piers by laying the bridge over them, adjustment pier placement as needed. Glue the bridge pieces in place using epoxy glue. Allow the glue to set for 15 minutes.
Glue the bridge into place, covering the abutments and piers. Place a dab of glue along each pier and along the abutment and then hold the bridge in place for 30 seconds to begin the glue setting. Allow a further 15 minutes for the glue to set.
Run the flex track over the placed bridge. Glue the cork roadbed for your track onto the surface of the bridge with epoxy glue, waiting 15 minutes for the glue to set. Place the track over the roadbed, and then connect the bridge track to the track on either side of the bridge to complete the installation. Glue the track to the roadbed by diluting white glue to a 25 percent solution. Brush the railroad ties of the track to the roadbed and allow the glue to set overnight.