Wednesday, March 17, 2021


During construction of a model railroad one occasionally (hopefully only that!) encounters a project that refuses to advance in a straight-forward manner in spite of seemingly sound construction practices.  Such has been my winter project--wiring the new track including four double slip switches at RR-East Eugene.  My previous post--now two and a half months ago--described the mechanical aspects of laying track and installing switch machines.  That post gave a hint of some of the frustrations I have experienced with this project:  tight working quarters, a shift of eyesight (cataract surgery) since original construction, and selecting and obtaining the required double slip switches.  Since then, I have experienced a model railroad "do-loop" (endless repetition of tasks with no progress).  


The earlier blog post on track laying described the addition of a second main track extending from the RR-East end of the Eugene depot trackage to the departure side of the arrival-departure yard--the reverse loop staging tracks in the "back" room.  Anticipating that I might want to add signals someday to this complex track plan, I decided I need to create two additional electrical blocks for the OS-block and new main track.  I decided not to run the full block wiring back to the Eugene electrical connection panel.  The new block bus wires extend only over the immediate area of the new track for feeder connections and then connect, for now, to the original block bus wires for these two detection block functions.


Track feeders were dropped and connected to the appropriate bus wires.  Similarly, connections were made to the switch machine terminal blocks to provide for electrically hot frogs (switching polarity).  All of this was relatively straight-forward in spite of the tight working conditions under the layout.  


I was often challenged to find the right optical help for my post-cataract surgery eyes.  Original construction of my railroad often found me removing my glasses for close work under the layout.  Presbyopia had been kind to my extreme near-sightedness, rendering good vision focus inside my arm-length without glasses.  Post-cataract surgery, with my distant vision now corrected to nearly 20/20, I now found this same viewing range required reading glasses or other magnifying lenses.  This has been a big shift for me and the source of much frustration as I need to change to the right range readers for work under the layout.  I continue to wrestle with this as old habits must be un-learned and new ones developed.


Pressing on, I finally got to the stage where I put a test loco on the track, fired up the DCC system, and tried running through the new track work.  No joy.  I had a dead short.  It took me quite a while to work through trouble shooting to locate the source of the short.  All of the wiring underneath looked good, but the short remained.  I finally isolated the new track electrically from the rest of the RR--disconnecting multiple bus wires back at the Eugene connection panel. 


I eventually identified the short as being within one of the new double slip switches.  Further investigation pointed to one of the two frogs shorting to one of the rails running through that frog.  I thought I might clear this by cutting new rail gaps.  No Joy.  I finally took the drastic step of removing the offending switch.  


Double-slip switch with frog short removed.  DAP adhesive caulk softens and releases when soaked with a pool of rubbing alcohol for 15-20 minutes.


Close examination of the underside of the frog revealed the source of the problem.  I am using Peco SL-U8363 code 83 double slip switches.  These feature a good mechanical design.  Peco makes these with their "unifrog" design which features a modest length frog that the user can decide to use as either a "dead" frog (no electrical connection) or a hot frog with a polarity-switching connection.  I use the latter feature.  Peco has done a very good job designing the switch so that it needs only four electrical connections:  the two stock rails and the two frogs.


Peco unifrog underside showing pass-through rail connection wires flanking the frog wire.  I have added a small bit of wire insulation to the frog wire as it passes between the other pair of bare wires.  This is a critical user installation requirement!


The photo of the underside of the Peco frog illustrates the problem and the solution.  Three bare wires are in close proximity, each potentially having an opposite polarity.  With contact between the frog wire and one of the two run-through rail connection wires, a short will develop when the frog is set to the opposite polarity.  It is very difficult to assure keeping the frog wire clear of the two run-through wires during installation, even if one knows this is a potential problem.  The solution is to add insulation on the frog wire.  I used a 1/4-inch section of insulation removed from a strand of Cat5 cable wire.  I threaded it onto the frog wire, pressed it down to the frog and then added CA glue to affix it.  


My earlier work trying to isolate the frog with additional rail gaps led to a loose rail on one end.  While I could fix this with solder and spiking the rail into position, I chose to order yet another new switch.  Once again, Yankee Dabbler ( came to my rescue by having it in stock and promptly shipping it.  Thank you!  When the new switch arrived, I added insulation on the frog wire and removed the throw-bar springs--unneeded with my use of Tortoise switch machines.


The new switch with appropriate modifications cleared that first short.  Unfortunately, as I began testing the new track-work again, I found yet another short on a previously untested routing.  This was in the double-slip switch at the other end of the group of four switches.  With experience, I quickly identified which frog was causing the problem.  Out came a second switch. I dinged up the cork roadbed quite a bit with this removal.  That prompted more delay as I had to let the alcohol-laden area dry out and then add spackle, paint and then gluing the switch to the roadbed with adhesive caulk.   Each step took frustratingly more time.  During the course of this removal, I ended up breaking solder joints for two of the feeder wires (one stock rail and one frog), so I had to repair those.  Somehow, I STILL managed to cause a frog short with the installation, so out it came--again!  


While I have been frustrated by the Peco electrical design that almost guarantees a short between the frog wire and one of the run-through rail wires, I remain satisfied with the modified product.  It has a sound mechanical design.


Just when I thought I had all faults corrected, I found I now had a dead frog for one routing.  Chasing my way back through the wiring underneath, I found I had a cold solder joint for one of the feeder connections to one of the bus wires.  Out came the resistance solder unit to fix that problem and to finally fully connect a couple of additional track feeders needed for short track sections used to connect the relatively short Peco switches in places formerly occupied by long number eight switches.  


I still need to create a new control panel for the new track arrangement.  The first panel will use toggle switches to control the switch machines backed up by LED route indicators.  Eventually, a second panel will be created that will use two-button entrance-exit (NX) control.  


Time to test the track and demonstrate that I now have two main lines in and now out of the arrival-departure yard!


A RR-East meets a RR-West, passing on the pair of tracks now connecting the Eugene depot to the arrival-departure yard.


The form of future Eugene operations.  A RR-West train departs the A-D Yard via the connection to the WP Siding in front of the depot while a RR-East enters the A-D yard from the main track at the depot and then curves left to take the arrival side of the A-D Yard.


This has been a long, frustrating, and challenging effort to provide a new traffic arrangement into and out of the Eugene Arrival-Departure Yard, aka staging.  It will be interesting to see how this plays out when we finally return to full operations with a full crew.  The track-wiring battle has been won, but the war continues.


  1. Outstanding Bill. Can't wait to mess it up, er' exercise this in it's success.

  2. Working under the layout is difficult for me too due to presbyopia and progressive lenses. That is one reason I opt for designs that have minimal under table work.

  3. Yoga guys. After I started yoga, soon after I found it easy to pretzle myself under a layout or the sink. Made the plumber snicker.
    Bill, why the excess distance between the yard tracks? That looks much beyond the standard 14 feet.
    D.A.Waggoner, SPinGalt.