Making switch locks from phono plugs and jacks
Thicker, lumber-backed fascias required a router to create a 2″׳₄″ depression in them about ³₈″ deep (above left). Holes were drilled to attach the chassis mounting board with a pair of screws, and some clearance holes were needed to provide space for the soldering lugs. To dress up the appearance of the switch lock, the author made a cover plate from K&S Engineer- ing .032″ aluminum sheet (above right). Adding a location name helps identify which turnout will be thrown. This is especially
useful when several turnouts are in the same vicinity. Here (be- low left) is the hardware club members use to attach the dual chassis in thin tempered hardboard fascias: 4-40׳₄″ screws, lock washers and nuts, along with a scrap piece of hardboard which is used for a spacer. This view (below right) shows how the installation looks in the fascia. Accurate drilling of the small mounting holes and larger RCA jack holes is essential for a neat appearance. A label to identify the turnout is optional.
about ³₈″ deep. A couple of holes need to be drilled
to attach the chassis
mounting board with screws; a few oth- ers will be needed to provide clearance for the soldering lugs and wiring. A cover plate was fabricated from some K&S Engineering .032″ alu- minum sheet to dress up the appear- ance of the hole created by the router. The final touch is a label with a loca- tion name to help identify which turnout will be thrown. This is espe- cially useful when several turnouts are grouped together in the same vicinity. Our newer modules are made of lightweight construction and the fascia consists of nothing but a thin layer of tempered hardboard. Thus, an alter- nate method of mounting the jacks needed to be found. It turned out to be a simple matter of drilling a few holes to allow the RCA jacks and chassis to be mounted from behind the fascia. However, note that it is critical to drill accurate holes in order to mount the
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jacks in this fashion, and you might want to make yourself a template. A simple template can be made from the dual RCA chassis itself by simply rip- ping out the metal connectors. This will leave only the plastic chassis with the proper-sized holes in it, which be- comes a handy drill guide.
One word of caution is in order here. The dimension between the jacks mounted on the chassis may vary. I have seen two variations in the dual chassis that I have bought. As a pre- caution, check the spacing of the jacks on the chassis to make sure they are all consistent before pre-drilling a bunch of holes in the layout fascia. In any case, two ¹¹₃₂″ holes are need- ed for the RCA jacks themselves, as well as two ¹₈″ mounting holes. If pos- sible, use brad point drill bits to pre- vent the bit from skating on the hard- board surface. The chassis is attached with 4-40×¾″ flathead screws, nuts and lock washers. A spacer should also
be added between the chassis and the hardboard so the jacks will end up be- ing flush mounted with the outside surface of the fascia. A scrap piece of hardboard will do the job. No routing is necessary with this method and the installation is very neat and clean. The need for a cover plate is also elim- inated since only the two jacks are ex- posed through the fascia material. This has become our preferred method for installing the switch locks. I hope you have found this article to be useful. The RCA switch locks have proven very effective and our crews like them a lot. They are not only easy, cheap, and do the job but they also help simulate the prototype chore of using a key to unlock a track switch that needs to be thrown. Most importantly, the crowds at train shows can’t accidentally throw turnouts and cause unintentional derailments, and nobody will snag a shirt sleeve on them because they are mounted flush with the fascia.
JULY 2012
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