Model Railroading > Hack for short reversing sections?

On my planned staging level I have an area where a wye, 2 reverse loops, and staging locations are all intertwined. Unless I make multiple tracks into reversing sections, there's no single section (or even multiple) that is longer than my planned trains. I am running metal wheels, but don't plan on lighted passenger cars or cabeese, nor running detection equipment (steam era, unsignalled). I'll be using Digitrax DCC, so auto-reversers are in the plan but not cheap.

What I'm considering is placing a 1/4 inch section of dead track at one end of a reversing section, such that a set of wheels can only bridge one side of the double gaps at a time. That should eliminate the normal concern of bridging both ends of the section at the same time, which is what causes issues for a/r systems. With traditional DC I don't think it would work, because the polarity of the reversing section is less fluid; a/r systems allow it to switch back and forth on the fly. Has anyone tried such an arrangement, and did it work as I'm envisioning?

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Darren Boes
Lethbridge, AB
Southern Alberta Railfan

Haven't done dcc for awhile ( dead rail), but I can't see that working unless you have one wheel pickup for your loco.  With standard loco pickup. Part will be in one polarity and another part in the other.  The two polarities will meet at your decoder, not good I think. I could be wrong though, I have been in the past.
john
 

SeaboardMan Wrote:
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> Haven't done dcc for awhile ( dead rail), but I
> can't see that working unless you have one wheel
> pickup for your loco.  With standard loco pickup.
> Part will be in one polarity and another part in
> the other.  The two polarities will meet at your
> decoder, not good I think. I could be wrong
> though, I have been in the past.
> john
>  

That's what the auto reversing circuit/system does. It senses that short, and flips the polarity of the reversing section before the command station reacts to the short. It replaces the DPDT switch used in DC, and does it instantaneously, on-the-fly, so the train keeps rolling as if there's no difference.

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Darren Boes
Lethbridge, AB
Southern Alberta Railfan

There are some recommendations about the electrical gap on the Internet, I beleive it would be from the manufacturers of the more complex auto-sensing and reversing circuits. It was something to do with placement of gaps and length of the gaps ( +basically the Circuit Breaker is faster than the Auto-Reverser under some conditions). Have to rely on doing a Google style search to find the exact info though.

Be aware of any of the all in one webpages, it's just more complicated that one summary can handle. The electrical issue has to do with how circuit designs react, mostly the circuit speed and which circuit reacts or shuts down first, some of the designers are slowing circuits and then changing the designs again very quickly. Keeping in mind that many designs can be programmed through JMRI or similar methods.

There are some discussion sites on Groups dot io also on MRH but quite a bit of that info has moved to FB as it's easier to update with new info. Good to get a discussion going though.

+ added the Circuit Breaker is faster than the Auto-Reverser...



Edited 1 time(s). Last edit at 01/01/25 13:00 by TCnR.

Is it possible for you to attach a drawing or picture of your track plan for this section?

-Sean

Track plan and schematic attached. HO scale, 3" centers on the hidden trackage.

Top left goes to phase 2, bottom of the wye goes into single track, then into a double track helix (with crossovers) up to the main level, and the pair of crossovers in the top right provide the reversing loops for both phase 1 and phase 2, allowing loop to loop operation on both. Trains coming from phase 2 will be able to head straight for the main level of phase 1 by going through the single track leg of the wye.

Letters A thru E on the schematic indicate staging locations.

Darren Boes
Lethbridge, AB
Southern Alberta Railfan

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As each individual powered wheel on a locomotive is NOT electrically isolated from the next, the length of the dead section "gap" must be as long as your largest powered truck. For example if you have a 6-axle diesel, one 3-axle truck will be electrically interconnected (as each wheel typically has a brush/contact) and so the length would need to be say 1.5" or so instead.  

JUTower Wrote:
-------------------------------------------------------
> As each individual powered wheel on a locomotive
> is NOT electrically isolated from the next, the
> length of the dead section "gap" must be as long
> as your largest powered truck. For example if you
> have a 6-axle diesel, one 3-axle truck will be
> electrically interconnected (as each wheel
> typically has a brush/contact) and so the length
> would need to be say 1.5" or so instead.  

That would apply to the reversing section as a whole, but I don't see the difference it would make in this scenario. Once the locomotive is bridging the regular track and reversing section, the auto reverse unit is supposed to correct any polarity mismatch. My idea is to prevent it from reading both ends at once if wheels hit both ends at the same time. With a short "double gap" regardless of where the locomotive is at the far end, metal car wheels bridging either set of the double gaps does not generate a short no matter the polarity at that set of gaps. I'm running steam, so a locomotive length gap is impractical.

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Darren Boes
Lethbridge, AB
Southern Alberta Railfan