Re: Reality Check Needed - See File and/or Read Description

Vollrath, Don <dvollrath@...>


You have done well to draw out the track plan using different colors to identify rail polarity. Note that one must traverse both the A and B double crossovers in order to reverse the direction of a train. It looks easier to me to isolate the polarity reversing issue at crossover B.


1.       At crossover B Provide isolating joiners at both frog rails on both of the lower turnouts leading to the diamond. The upper turnouts and the diamond of B remain fixed at the polarity of the outer loop.

2.       Determine the maximum length of a train. Follow the inner loop tracks of the figure 8 from crossover B about that same distance in both directions from B. This is where you need to place additional isolating joiners or gaps on both rails for the minimum practical length of auto-reversing track.

3.       Going CW from B, I would put insulating joiners at the point end of the siding turnout at the 6 o’clock position of the loop. If that is not far enough from B, put them at the point end of the three-way turnout, keeping the lower turnout and siding as part of the isolated loop.

4.       Going CCW from B, I would place isolating gaps past the overpass, maybe near the 5 or 6 o’clock position of the left loop of the figure 8… or even at the turnout near the 10 o’clock position.

5.       That isolated track segment, including the two lower turnouts at B, form the polarity reversing section. Wire those tracks to the AR-1 auto-reverser.

6.       All other tracks on the layout including crossover C are constant polarity. Be sure to provide plenty of track droppers for adequate DCC connections.


You could interlock the double crossovers of A and B, but it is probably not worth the effort. That would also prevent the opportunity of a long continuous single train run overall of the mainline tracks in both directions.

For simplicity I recommend providing a single PB or toggle switch to select ‘straight’ or X-over for all 4 motor controlled turnouts at each of the double crossovers. Then there is no need to fiddle with multiple switches.  


If you plan on multiple operators. It might pay in the long run to further isolate the figure 8 loop into two pieces by adding insulating joiners at B on the straight track between the two lower turnouts. For now wire those tracks up to the single AR-1. But in the future you may want to add a 2nd AR-1 for independent multiple train operations at the industry tracks while another train uses the overpass. You may also want to isolate the yard under the overpass from the A crossover, and feed it via an electronic CB protected district.




From: WiringForDCC@... [mailto:WiringForDCC@...] On Behalf Of Rick Allison
Sent: Tuesday, February 04, 2014 9:43 PM
To: WiringForDCC@...
Subject: [WiringForDCC] Reality Check Needed - See File and/or Read Description


I'm putting together my first layout in 40+ years-and I have a couple of wiring questions. I've read through Alan's website but have not found an example that matches my situation, so before I build it I thought it best to come here for a reality check.


The layout is a fairly simple 5x9 consisting of two concentric loops surrounding a figure 8. There is a Walthers/Shinohara "DCC-Friendly" double-crossover connecting the concentric loops at the 6 o'clock position, but wiring that should be pretty straightforward. Where it gets tricky is this:


There is also a double crossover between the inner loop and the left-hand lobe of the figure 8, at about the 11 o'clock position. The top of the right-hand lobe of the 8 is elevated over/above the inner loop, and there is a double-crossover between that right-hand lobe and the outer loop at about the 1 o'clock position.


Both of those double-crossovers each use a Walthers/Shinohara curved turnout plus three Atlas turnouts tied together with a 45-degree crossover. (See file HORRTG Layout Polarity Plan.jpg.)


My main question is: With insulating joiners separating the 45-degree crossovers from their respective inner and outer loops, can I use a single auto-reverser (like a Digitrax AR1) between my booster/bus and the figure 8, thereby reversing polarity on the entire figure 8 when an engine crosses over to or from either the inner or outer loops? Or do I need an auto-reverser near each of those double-crossovers? Or...?


Secondary question--although it's a small layout running 3 engines tops, is it worth setting up those two crossovers in such a way as to prevent two engines hitting the reversing figure 8 at more or less the same time (wiring the switches to ensure only one crossover can diverge at a time, or wiring the crossovers with a sensor so that if one is in use the other is de-powered, for example?).


Sorry for the lengthy description; hopefully I've got the ''HORRTG Layout Polarity Plan' file or Picture uploaded correctly to better explain what I'm trying to do...


Thanks in advance for your guidance,


- Rick


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