Installing Caboose Ground Throws on MTH Scaletrax Switches
This weekend, I completed the installation of Caboose Industries ground throws on my Scaletrax switches. For those of you who use Scaletrax (despite its periodic fickleness and scarcity), I thought a description of my installation process might be helpful and encourage some to try it. I continue to be a fan of Scaletrax, as I've found it relatively easy to work with and it remains the most realistic 3-rail track out there.
First, however, I must mention the great debt I owe to the Scaletrax master, Dave Hikel, whose OGR forum posts from several years ago inspired me to try this method. I corresponded with Dave via email several times immediately prior to starting this project, and he was unfailingly kind, helpful and timely in his responses. I have included a few steps and techniques that were not in Dave’s original instructions, but which worked well for me and my modest skills. Feel free to modify the installation steps described below to suit your own needs—and have fun with ground throws!
Begin by removing the original throw bar by cutting the tabs with a Dremel tool and cutoff disc [Photo 1].
Cut a piece of .080 x .156 styrene strip 3” long for new throw bar. Make a mark on the throw bar 9/16” from the far end (opposite the ground throw side).
Cut two pieces of .040 x .156 styrene strip 3/16” long; these pieces serve to build up the sections on the throw bar where the switch points will be attached.
Glue the first piece of 3/16” styrene to the top side of the throw bar so that it aligns with the mark on the throw bar. Before gluing the second 3/16” piece, measure 13/16” from the approximate center of the attached first 3/16” piece; mark the side of the throw bar accordingly. This is an important step. When I made my first attempt, I didn’t mark the second piece carefully and found the eventual track gauge too wide and had to make a whole new throw bar assembly. Glue the second 3/16” piece on top of the throw bar so that the approximate center of the piece aligns with the mark on the side [Photo 2].
Cut a piece of .040 x .156 styrene strip 3/4” long and glue it to the underside of the throw bar flush with the ground throw end of the throw bar. This is optional, but I found it was helpful in keeping the installed throw bar level throughout the range of motion.
Using a pin vise and #52 drill bit, drill a hole in the center of the 3/16” piece that is furthest from the ground throw end [Photo 3]. It’s ok if the hole goes all the way through the throw bar. Measure 13/16” from the center of the just-drilled hole to the second 3/16” piece on top of the throw bar and mark it. Drill a similar hole using the mark. The main thing is to make sure the centers of the two holes are 13/16” apart; it’s not that critical if the holes are not in the exact centers of the 3/16” pieces. Try to align the holes horizontally as well when you’re drilling, but as long as the holes are reasonably well-aligned, the ground throw mechanism will work fine [Photo 4].
To accommodate the Caboose ground throw, the ties of the Scaletrax switch need to be extended. Cut four pieces of .080 x .156 styrene strip 2” long. Glue two pieces together in order to make one piece .160 x .156 x 2”. Glue the other two pieces together in the same way [Photo 5]. You can also use O scale wood ties for the extensions instead.
Paint the assembled throw bar and the two tie extensions. Raw umber is almost an exact match for the brown plastic of the switch ties. I used Liquitex brand raw umber, but any acrylic paint will do. I painted each piece twice to ensure decent coverage of the white styrene.
If you can find them, use 1-72 x 3/8” flat head miniature brass screws. I couldn’t find any 3/8” long, so used two 1-72 x 1/4” and ground the ends so that they were close to 3/8” long. I used the Dremel with a grinding wheel to do this [Photo 6].
Screw the miniature screws into their proper holes in the throw bar [Photo 7]. The screws will cut their own threads in the plastic, but it’s much easier to do the final assembly of the throw bar if the threads have already been cut. Unscrew the screws from the throw bar and set them aside.
Since I use cork roadbed as a base for my track, I needed to create a base for the ground throw at the same height as the track roadbed. I cut two pieces of Midwest cork roadbed each 1-1/2” wide. Using Woodland Scenics foam-tack glue (any white glue will work), I glued the first cork piece upside down on the tabletop so that the beveled edges of the base piece and the existing roadbed aligned to form a solid joint. I then glued the second piece cork piece right side up and aligned the straight edge of that piece with the straight edge of the previously-installed piece [Photo 8].
Once the base has been built and the glue has dried, glue the two tie extensions in place on top of the base. Place each tie extension flush with the ties of the switch on either side of the eventual throw bar location. The tie extensions should be parallel, with a 3/8” gap between their inside edges. I attached the tie extensions to the cork base using the foam-tack glue [Photo 9].
Using the pin vise and #54 bit, drill a hole in the center of the throw bar 1/4” from the end opposite the two previously-drilled holes. This new hole will accommodate the pin on the Caboose ground throw.
Take the throw bar assembly and insert it under the rails into the same place where the original throw bar was located. Align the throw bar so that the inside rail switch point hole is over the corresponding hole in the throw bar. I then slid a spare piece of .080 x .156 styrene strip under the throw bar to create a firm base against which to insert the miniature screws. Attach the points to the throw bar using the screws. Don’t over-tighten the screws, as a bit of play is necessary for proper operation [Photo 10].
Once the two tie extensions have been installed and the glue has dried, take the 208S Caboose ground throw and insert the pin into the hole in the throw bar. Ensure that the switch points are in the center of the rails (i.e., not touching either outside rail) and ensure that the ground throw is centered (i.e., the lever is straight up). Then align the ground throw on top of the tie extensions so that moving the ground throw lever to each side aligns the points with the stock rails. Once you’ve made sure the mechanism works properly, mark the top of each tie extension using the pre-made holes in the ground throw. Drill a hole through each tie using the #54 bit and attach the ground throw using 1/2” x 19 wire nails [Photo 11]. Paint the nail heads black—and you’re done! [Photo 12]
Test the installed ground throw mechanism with your trickiest piece of rolling stock and your most temperamental locomotive to ensure proper operation.
