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Discussion Starter · #1 ·
Hi all - first post here and new to model railwaying (well, since I was a kid!)

We've bought a Virgin DCC set for our son for Christmas, plus another second hand DCC engine from his grandparents. Ain't he the lucky one?! Anyway, as is so often the case, space is tight so we've had to be quite creative with the layout.

We decided the best bet was to have a long straight along one wall in his room, which runs into a sort of circular section. The grand plan (or at least part 1 of it) is to be able to run the trains up and back on double track, then go either way round the circle. 6 points in all to allow the train to go around in the circle, or go back and then switch from one straight track on the double track section to the other.

Now, assuming I've managed to describe that coherantly, I'm imagining some of you are already shaking your heads! My initial reading on DCC essentially said "now you can design any layout you like without worry", which is what I did. But it was when I saw a Hornby DCC "reverse loop module" just now that I began to think... hold on, I thought I could do anything?! Why would I need one of those?

So as I can be prepared for the Christmas traumas, I'd love some advice! Will our layout work? Will it need some modifications or extra bits of kit / isolating things? Apologies for being so green!

PS - there looked like a relevent section to cover this in the DCC FAQ, but it was empty?
 

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Discussion Starter · #4 ·
Thanks to you both - Richard, yes I do see what you mean. I've found a helpful (if daunting) website at http://www.wiringfordcc.com/track_2.htm#a39. My proposed layout looks similar to figure 2 under the heading "using double crossovers with balloon tracks", about 3/4 of the way down the page (differences are that there will be 2 straight tracks to the end, and the bulbous bit has a optional circular loop built in). I think I understand his solution, but can I just check it with you fine people?!

The train (say) goes up the RHS from bottom to top. It hits the reverse section. First question - what actually happens at this point? The train is going forwards, and presumably still does, it's just the polarity changes, right? Assuming I have that right, round it goes (round and round with my optional circle til eventually...) it comes back down the LHS. At which point the polarity switches again, so now it is the same as when it started, and the points are set so it switches back the RHS. But that is OK... with DCC the train is clever enough to know which way it is heading, and we've broken a potential short circuit. Positive and negative has no effect on train directions, right? It's just you mustn't inadvertantly directly connect one to the other. Perfectly logical.

I note the author says that the reversing section has to be as long as the train. That's OK in this case - I reckon a 2nd radius semi circle is pretty much the same length. However, I don't fully get why. With the Pendolino, it has lights at the rear of the train. Surely as it crosses over, the front of the train is one polarity, but the rear is another, causing problems? Or does current pass through the train somehow?

So if I have all of this right (and I suspect I don't), why do I need a reversing module at all? Wouldn't simply isolating that top section do the same job? Bear with me... I'm slowly getting this, but not quite there yet! Really appreciate the help...
 

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Discussion Starter · #6 ·
Thanks zmil - I get the isolation, but still a little confused on what happens when a train passes over - won't the front part have one polarity, and the rear another? And could someone explain why the isolated section must be at least a train length long when clearly the train must be in two zones at once to get there in the first place? Thanks for your continued patience!
 
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