C-TRACK CENTRE STUD DETECTION TRACK
BY STEPHEN COOK
WELLINGTON - NEW ZEALAND
Written for members of The Märklin Mailing List (MML) as per the thread 3 Sept. 2000.
These steps below show how I made a detection track using a piece of C-Track. In this instance I have used a half-straight number 24094 but the technique can be applied to almost any piece of C-Track.
The detection method utilises the ability to sense the potential of the Märklin center-rail. A short section of the center rail is isolated and as the pickup shoe travels across the isolated section, the shoe completes the circuit, placing the center-rail potential onto the isolated section.
It should be noted that my original intention for this project was for use with the S88 (or equivalent) digital detection module. However it can also be used in conventional operation but should be used via a relay and you must pay close attention to your wiring. If you are not sure what you are doing... Don't!!
For those wondering about feeding the "hot" rail into an S88, it is actually a similar technique as used for indexing the Märklin Digital Turntable. As always this is a "home-brew" project and I am not liable for any problems you may encounter.
For this article I have chosen to make the detection section 3 studs in length, but further experiments indicate two studs are better. Whatever length you choose, keep the following points in mind…
For an immediate visual indicator of how this works, simply connect a lamp (or LED & Resistor) to your new detect section and watch it operate as the shoe passes over.
TIP *** M & K TRACK - This technique can also be used without any track modification using M & K track. You will need the very short make-up pieces (M-5208, 5210, 5211) or (K-2204). Simply isolate the centre rail from the track on both sides and attach a wire to the isolated centre rail to detect from. You will probably find the shorter sections best.
I would appreciate the feedback of others who have tried these suggestions, what your own experiences were, and any suggestions for improvement. My apologies for some of the image quality.
STEP 1 - Start to remove the center stud rail from one end by pressing down firmly on the first stud with a small screwdriver.
STEP 2 - Place a small screwdriver between the end of the center rail and the underside of the track-bed. Using a second screwdriver, press down on the silver connector plate (the stud is pressed through this plate at this point).
While holding the silver plate, lever the other screwdriver upward to release the center rail from the connecting plate.
Repeat this process at the other end, then turn the track over. Continue pressing each stud down through the track-bed until all are free and the center rail can then be completely removed.
Picture of Track with the center rail removed
The removed center-stud rail. Note the shape of the stud "heads". This is what actually holds the rail securely within the plastic track-bed.
STEP 3 - Cut the center rail to isolate the desired section. The rail is made of soft metal and side-cutters work just fine. You may need to snip off a small further amount to ensure there can be no adjacent contact when reassembled. File the ends for a smoother finish.
STEP 4 - Fit the two center rail end pieces back into the track-bed and press firmly into place.
STEP 5 - File the bottom of the removed center rail section to expose a clean shiny surface and tin with solder. A feeder wire can now be soldered to the section. I have used BLUE colour wire to maintain consistency with Märklin accessories.
STEP 6 - Fit and press the section back into the track-bed and check that there is no connection on either side. You may prefer to secure the short section more firmly, I have used a small amount of hot-glue and it's perfect (not shown here).
THE FINISHED TRACK PIECE J