Live Frog turnouts are generally recognised as the most reliable type of turnout because their common crossing is solid metal and therefore, maintains electrical continuity and prevent trains from stopping, however, as supplied, there are a number of traps for novices; namely dirt giving bad contact between the stock rails and the switch rails and shorts between the stock rail and switch rail due to oversized wheels or wheel overhang due to slack in the bearings, particularly with locomotives with three driving wheels pairs as all three wheels sets can't be in contact with the stock rails on a curve. This problem is often overcome on 'Train Sets' by using 'Insulfrog' turnouts.
The wiring of live frog turnouts is a topic which frequently arises in most model railway groups but is unfortunately, not well explained.
In this article, we cover the correct wiring method for live frog turnouts. The technique will be applied here to a Peco Code 75 turnout, but apply equally to Peco Code 100 turnouts manufactured later than the turn of 2010/11. The technique can be applied to earlier versions with a few modifications.
Let's start with a picture:
Peco code 75 and current code 100 turnouts are actually manufactured to make the process of wiring them correctly extremely easy but they do require a few minor modifications.
The main objective of the modifications which follow is to divide the turnout up into 3 electrically separate areas: the two stock rails (which remain powered at all times) and the crossing V which is fed via a switch, the polarity of which is determined by the setting of the turnout.
The first modification is to break the wire jumper on the underside of the turnout marked with yellow lines.
On the top side, there is already an insulated break in the rails.
Earlier Code 100 turnouts did not have this insulated break, therefore it was necessary to use a cutting disc to cut the rails.
The next modification is to electrically bond (connect) the switch rails to the stock rails, marked by red lines. There is a gap in the sleeper webbing to enable this. On older Peco products such as code 100, it is quite easy to cut the same gap using a knife.
The purpose of this modification is to remove the reliance on the switch blades making electrical contact with the stock rails. It also ensures that the switch rails are always at the polarity of their neighbouring stock rail and therefore stops any shorting or sparking occuring between them due to out-of-gauge or course scale wheels.
In the picture we have shown a Peco switch as these are often used because they fit easily to Peco motors. Any switch will be suitable so long as it is at least a SPDT two-way switch.
The wiring should be connected to the switch as shown by the red and blue lines.
Finally, insulated fishplates should be fitted to both of the crossing V rails, marked with green lines. This ensures that the entire crossing V area is a single electrically isolated unit with its own feed. This prevents the turnout causing shorts due to a feed from the back-end instead of the toe end.
The turnout is now ready for installation on your layout.
While we have demonstrated the wiring method as applied to a Peco product, the technique is exactly the same as that used for hand-made turnouts, whether they are copper clad, spiked, Peco Individulay, C&L or P4 Track Company. The technique applies equally to all model scales, although is more difficult to implement in the smaller scales such as 2mm and 'N'.
The technique above is often referred to as 'DCC Friendly'. This term is incorrect because it implies that there is a special way to wire turnouts for DCC when in fact, this is not the case. The technique above is simply the correct way to wire live frog turnouts, regardless of scale or traction control method (DC or DCC).
Graham Plowman (Updated 26/05/2019)