Author Topic: Is this complex reverse loop possible? (DCC)  (Read 1248 times)

0 Members and 1 Guest are viewing this topic.

peteski

  • Crew
  • *
  • Posts: 28790
  • Gender: Male
  • Honorary Resident Curmudgeon
  • Respect: +3359
    • Coming (not so) soon...
Re: Is this complex reverse loop possible? (DCC)
« Reply #15 on: September 01, 2020, 04:02:27 PM »
0
I always wondered about this, as in, why is an auto-reverser even needed with DCC?  So this is the trick?  It's just a matter of the two sections being out of phase?  And all the auto-reverser does in a DCC system is align the two phases?

It is needed because of the physical rail layout. In a reverse loop the tracks returning back to the start of the loop have their rails crossed to the other side.  This is is just their physical layout, regardless what type of voltages are passed through them.  So, when the train completes the loop, the polarity of either the main line, or the loop has to be flipped for the train to continue running.  That is clearly apparent in when looking at it on DC layouts.  DCC is just a DC voltage that flips multiple times a second. So instead of saying that if polarity is not flipped it will short out, I just said that the DCC signal is (180 degrees) out of phase. Because it is. But physically, it would be the same "short" as in DC.
. . . 42 . . .

CRL

  • Crew
  • *
  • Posts: 2261
  • Needs More Dirt.
  • Respect: +574
Re: Is this complex reverse loop possible? (DCC)
« Reply #16 on: September 01, 2020, 04:29:39 PM »
0
CRL, I don't think so, but it might be that my gap drawing was not clear enough.  Here is a blow-up showing that there are two gaps in the upper section, past the frog of the lead turnout:



I don't see any way for a train to reverse direction in this yard without having to cross one of these gaps.  I am also assuming that two trains will never cross two gaps simultaneously, lest they foul each other.  Strictly speaking you could voilate that if a loco sneaked out beyond one of the paired gaps while a train was crossing the outer gap, but that's always a risk.

I agree that it's nice to have, but it's not a requirement for this situation if, for example, cost is a factor.

You’re correct... you’ve got 2 tracks gapped... not one like it looked on the smaller scaled diagram.

kevlarcat

  • Posts: 16
  • Respect: +5
Re: Is this complex reverse loop possible? (DCC)
« Reply #17 on: September 01, 2020, 04:46:47 PM »
0
Awesome I've learned more about reverse loops out of this than any of the other info I found before, thanks!  I think what was messing me up with locos getting forced to change direction was an old discussion I found about running DPUs on trains through reverse loops, that it wasn't possible or something.  Ive looked at so much lately hard to keep it all straight.

Correct me if I'm wrong, but they look like Peco turnouts. In which case, the derailment rate would be greatly diminished.

Yes its N Peco code 55.   The amount of curved turnouts has made me uneasy as well, especially the double crossover section.  I only have it there because of the prototype, who has that because of frequent failures in either of the coal dumpers, and that could make some interesting operations trying to work with pretending one is out of service on a busy port.  In my research people claim the Peco curved turnouts are very good and no different than their normal switches. There should rarely be pushing through the crossovers, only pulling.  My biggest fear was the wiring so now that that is sorted I may try to lay the track as planned and heavily test.  If it fails ill just remove the crossover section.

As for the yard throat curves, I'm just doing the typical maximize yard track length before the forced 90 because of the wall, thats the best I could come up with. Straight ladders seem to eat up a ton of real estate.  Still new to the program though!


CRL, I don't think so, but it might be that my gap drawing was not clear enough.  Here is a blow-up showing that there are two gaps in the upper section, past the frog of the lead turnout:



I don't see any way for a train to reverse direction in this yard without having to cross one of these gaps.  I am also assuming that two trains will never cross two gaps simultaneously, lest they foul each other.  Strictly speaking you could voilate that if a loco sneaked out beyond one of the paired gaps while a train was crossing the outer gap, but that's always a risk.

I agree that it's nice to have, but it's not a requirement for this situation if, for example, cost is a factor.

I'm glad this was clarified with the zoom in, I would have missed that detail and possibly messed it up.  Thanks

peteski

  • Crew
  • *
  • Posts: 28790
  • Gender: Male
  • Honorary Resident Curmudgeon
  • Respect: +3359
    • Coming (not so) soon...
Re: Is this complex reverse loop possible? (DCC)
« Reply #18 on: September 01, 2020, 05:45:01 PM »
0
I agree that it's just one big reverse loop.  I think you can just put gaps at the red ticks here:



Then feed the entire yard off of any auto-reverse circuit.

Gary, why not jut gap both legs right after the first turnout of the reverse loop?  What does moving the gap further in to the 2nd turnout and then having to gap 2 tracks coming out of it accomplish?

While unrelated to Gary's comment, it is good practice to stagger the gap on each rail.
. . . 42 . . .

ednadolski

  • Crew
  • *
  • Posts: 4319
  • Respect: +1206
Re: Is this complex reverse loop possible? (DCC)
« Reply #19 on: September 01, 2020, 06:37:00 PM »
0
Gary, why not jut gap both legs right after the first turnout of the reverse loop?  What does moving the gap further in to the 2nd turnout and then having to gap 2 tracks coming out of it accomplish?

It's hard to see in the drawing but there actually is a reverse loop there too.  If you picture a train going thru either leg of that 2nd turnout, it can eventually come back thru the other leg in the opposite direction.

When I first looked at it I thought it was two (sort of nested) reverse loops, but if you gap it the way Gary illustrated then all you need is one reverser.


Ed
« Last Edit: September 01, 2020, 06:40:39 PM by ednadolski »

peteski

  • Crew
  • *
  • Posts: 28790
  • Gender: Male
  • Honorary Resident Curmudgeon
  • Respect: +3359
    • Coming (not so) soon...
Re: Is this complex reverse loop possible? (DCC)
« Reply #20 on: September 01, 2020, 06:50:58 PM »
0
It's hard to see in the drawing but there actually is a reverse loop there too.  If you picture a train going thru either leg of that 2nd turnout, it can eventually come back thru the other leg in the opposite direction.

When I first looked at it I thought it was two (sort of nested) reverse loops, but if you gap it the way Gary illustrated then all you need is one reverser.


Ed

Now I see what you mean - thanks!  "Nested reverse loop" is a good description.
. . . 42 . . .