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Electro-frog points made easier

Imagine a scene where a train is entering a yard through several sets of points. It has sound and lights and is moving at prototypical yard speed. Behind the engine are three lighted passenger carriages and a brake van.

The guard has the inside light on and the red marker lamps lit. The train moves slowly through each point, all the lights remain on and the sound continues without a hiccup.

You note that the rail is weathered, fine-scale Peco Code 75, making the whole yard scene very realistic. What you are seeing are electro-frog points in action!


Then why do many modellers shy away from them in droves or believe that they are far too difficult to connect up? Or is the electro-frog point just a secret for only those few?


What are electro-frog points?

As the name suggests electro-frog or live frog points have the frog or V section rails electrically powered. Like the prototype, these rails are all metal. Every metal wheel that runs over the frog picks up track power.



Why insul-frog points?

If you look at the picture you can see that as the locomotive moves straight through the point, the inner rail is the red rail and the outer is the blue rail. No problems here.

Now change the point. As the locomotive moves into the other siding, the wheels are moving from the blue rail to red rail at the frog and then back to blue rail. This will cause a momentary short circuit as the metal wheels contact the frog. There would already be a short circuit anyway because of the red and blue rails being joined.


So the manufacturers decided to make the frog or the V section insulated to stop the short circuit. They did this by making the frog from plastic. They also decided to power each closure rail from the contact point to stop the wide metal wheels shorting between the rails.

This makes them very easy to connect and was great for our first train-set when we ran trains at full speed through the points. The down side is the power goes dead in the siding when the point is switched. Small tank locos and shunt locos and those with few pickups stumble and stall on the dead or insulated frog if they go too slow. Sound locos can have the sound stop and then restart, lights in coaches and locos flicker on and off, all not very prototypical.

With the advent of DCC, loco decoders need full power in every piece of track, so having a dead spot at each point doesn’t help. Sure larger locos and those with all-wheel pickup don’t have a problem, and if you run your smaller locos at slot car speeds, they will get through most times.


How do electro-frog points work?

Two things are needed in the electro-frog point to make them work. And if you add a third you will make them work perfectly.

  • The first is a way of isolating the frog from both joining rails and the closure rails.
  • Second is a way of changing the polarity of the frog (from red to blue, blue to red) each time the point is changed. This is to make the polarity of the through rails the same.
  • Thirdly by powering both closure rails full time, you no longer need rely on the contact point at the stock rail to provide the power.


Most manufacturers of track include insulated rail joiners as part of their track-ware. Insulating both rails at the end of the frog solves the first concern. Regardless of the frog polarity (red or blue) a short circuit will not occur with the mainline or siding rail. Not too difficult so far?

If we wire the frog to a simple switch, we can now change the polarity as we change the point. With the frog isolated from both the running rails we will not short circuit.

Go one step further. Power the point with a motor and we can get the motor to operate the switch. Not too difficult so far?

Peco and Southline each make switches that you can add to a Peco solenoid point motor. Cobalt and Tortoise are slow motion point motors that have switches built into their circuits. Cobalt include a simple wire connection that does not require soldering. The one in the picture moves nice and slow using a surplus power supply giving 9volts DC. You can see the orange switch connections at the bottom of the motor.


electrofrog points cobalt

To make electro-frog points 100% reliable you can power them full time by adding a short jumper wire between the stock and closing rails. This is done for these rails on the red side and on the blue side. This makes certain that power is always at these rails rather than just rely on the electrical contact between the closure blade and each stock rail. Yellow arrows point out these contacts below. Stock and closure rails for red and blue are also shown.



To do this, remove 40-50mm of insulation from some thin copper hook-up wire and tin with a hot soldering iron. From underneath the point, tin both sets of rails and solder a jumper wire across each pair. Trim to length so it won’t be seen. The picture shows the details.

You can see the underneath of this Peco electro-frog point. The frog wire shown in green will join to the common terminal of the switch, with insulated joiners needed at both frog rails.

Yellow arrows show where you cut the thin wires as per Pecos instructions. A simple twist of a small blade screwdriver does it.

Red and blue represent the two short jumper wires across each set of closure and stock rails. If your point does not have this gap you will need to remove plastic to gain access to the bottom of the rails on both the red and blue sides.

For a very small amount of effort you now have a point system that will work every time.

Copyright © February 2013

Rodney Beauchamp   End of the Line Hobbies