An Automatic Reverse Loop for D.C.C.

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A simple alternative to electronic auto-reverser circuits. The diagram below is one way to automatically reverse the DCC polarity** for a simple loop. Please note that this approach works best with a simple loop which has only one way in and out. This includes the third leg on a simple wye. The toggle switch is shown mechanically linked to the throw bar as in the Saskatoon Railroad Modellers' hand laid gauge 1 switches. But Double Pole Double Throw contacts tied to a switch machine could also be used. Or Atlas makes a "Snap Relay" that can be wired in parallel with twin solenoid switch machines to give D.P.D.T. contacts. In fact, any fast acting D.P.D.T. contacts that throw with the track switch are suitable. Slow acting contacts, for example Tortoise switch machines are not suitable as they have a relatively long open time between contacts which leads to hesitation of the engine. The diagram shows wiring for non route selective track switches. For route selective switches which route power to either one route or the other (this includes the Saskatoon Railroad Modellers' hand laid switches) you can eliminate the inner gaps so that the toggle switch also switches the frog, backing up the contact of the points to the stock rails. When you wire the toggle switch or contacts, there is a chance that the toggle switch will be out of sync with the track switch and will cause a short circuit. If this happens, simply reverse either the feed wires from the main line or the feed wires to the loop (but not both.)   ** strictly speaking, we should speak of the phase of the d.c.c. power as it is a.c., but it has so often been refered to as polarity in analogy to d.c. circuits that the term is also used here. If you liked this article, let us know.  If you didn't, let us know why.  Your feedback helps us improve our site.