Monday, December 1, 2014

How to Electrify a Frog

Some of you may remember that since May I've been slowly documenting my attempts at point control (here, here, and here). All the posts so far have dealt with the mechanical side of changing the points and have completely ignored what happens to the power running through the rails.

In theory the PECO points can be used straight from the packet, but from prior experience I won't be doing that ever again. The problem is that, as manufactured, the points rely on the contact between the switch and stock rails to provide power. While this works well with a new point as soon as you try and paint, weather, or ballast the track it is exceedingly likely that the point of contact will be obscured and the power flow will either stop entirely or be very temperamental. On Jerusalem, I had no end of problems with the one scenic point and no amount of careful cleaning would give me a reliable point. The solution to this is to perform a small amount of surgery on the point so that we no longer rely on the contact between the rails to transfer the power.

Before we start altering the point we need to ensure some consistent terminology so that the instructions are clear. So here we have an annotated photo of a right hand PECO crazy track OO9 point.

Now that we are all on the same page here are four simple steps to upgrade the point.

Step 1
Counting from the vee end of the point, use a small razor saw to remove the webbing from under the inner vee rails between the first and second sleepers and also the webbing from under all four rails between sleepers six and seven (helpfully these are the sleepers with writing on the bottom). Be careful not to cut into the rails and try and make sure the sleepers don't slide along the rails.

Step 2
Add a small amount of superglue (the runny kind not a gel) at each point indicated in the photo. Capillary action will help draw the glue into the gap between the rails and sleepers and will help to hold the point together. Once the glue has dried use a small file or fibreglass pen to clean the newly exposed rail surfaces.

Step 3
Solder three wires to the rails as shown. Do not rush this stage as it easy to destroy the point by getting it too hot. My approach was to wrap as much of the point as I could in wet kitchen paper and to allow the rail to cool completely between soldering each joint. The three wires give you access to the track power (red and black) and the vee (white) and can be wired directly into most accessory switches found on point motors. If you don't need access to the track power (i.e. you are feeding the accessory switch from a power bus) then you can remove the left over black and red wires just leaving the bridges between the switch and stock rails.

Step 4
The final step is to electrically isolate the frog and vee from the switch rails. Use a small piercing saw to cut the rails just to the right (when viewed from below) of the sixth sleeper. If you can avoid cutting the webbing then the point will be stronger but I found this impossible with the saw I used. The point can now be connected to the rest of the track not forgetting that you will need to use isolated rail joiners on at least the two vee rails to avoid a short circuit.

When viewed from the top the changes appear minor and the wires can easily be dropped through holes in the baseboard out of sight. The main advantage, as discussed earlier, is that the point can now be painted and ballasted without worrying about retaining a clean contact surface for the switch rails as they are always at the same polarity as the accompanying stock rail.

I'm not going to go into the issue of wiring the point up as this has been covered elsewhere (a quick search for DCC friendly point wiring will set you on the right track) and can be done in a number of different ways depending on the switches etc. you want to use. At some point I'll wire these up to the Cobalt-S lever and have the power switched over at the same time as the servo moving the point, but I know some people will prefer using a micro-switch activated by the moving tie bar etc. Whichever option you choose if you've followed these steps, and not destroyed the point (I killed at least three before I got this worked out) then you should never have an electrical contact issue ever again!


  1. Mark

    There is still a long term electrical failure location with the PECO points (most gauges) and that is the switch rail pivot. If you have a good look underneath you will see that the switch rail is held in the metal pivot by two flat tabs of the folded switch rail that have been opened up to retain the switch rail. Now this means that the electrical connection is relying on the four edges of these tabs touching the circular metal pivot.

    Unfortunately the connection can begin to fail after a lot of use, I have had it happen.

    To eliminate this issue I have soldered a very fine wire (DCC decoder wire from ESU) around each pivot. You can solder a wire to each of the wires that you added (red and black) and the other end of each wire to each switch rail.

    I used a motor tool and a cutting disc to carefully carve a groove underneath the centre of the sleepers to run the wires in, holding them in place with some tape.

    This will make the points failure proof.

    Ray P

    1. That's interesting, thanks Ray. I had wondered about the hinge before, mostly as I was worried that glue from ballasting might cause a problem but I'd not thought about them failing separately. Will have to have another look at the points to try and protect against this.