DCC reverse loop confussion

[thatmanmongo]

Hi

 

I'm about to start construction of my DCC layout. The layout comprises of a twin track circuit that branches off to a terminus. To get trains back to the station, I would like to fit a reverse loop. I know how to wire a single loop but I'm unsure on how to wire and isolate a twin track reverse loop. I have attached a picture of a rough idea of the main line and the reverse loops. The crossovers that feed into the loops are a double slip at the bottom left and a single slip at the top right. Any help would be much appreciated.

 

Thanks

[Phil S]

The 'first assumption' is likely to be that the reversible section(s)  is(are) part of the diagonal tracks:

As shown, your main problem might be the lack-of-length of a reversible / 2 reversible sections - because the train needs to be wholly contained within the reversible section when the polarity is switched from matching the entry, to matching the exit.

 

IF your trains are restricted to plastic wheeled stock, other than at the loco end, then you might get away with a loco+ length of changeover on the diagonals.

But, even if the stock is not illuminated; metal wheels could be shorting the 'entry' whilst the loco is crossing the 'exit'

 

Therefore, you may need to look at the problem over a wider area .... and perhaps consider the curves to be the reversible track(s), with the diagonal;, and pointwork, as the 'fixed' reference polarity.

 

or run only short trains.

 

This is the sort of puzzle you can overhear being discussed in 'continental' model railway shops when the staff explain to parent's how much easier '3-rail' (actually centre-stud-contact) is to wire than 2-rail ..... even though Marklin only make 3 rail in H0, and not G,1,0, N or Z 8-)

[thatmanmongo]

The reverse sections will be able to hold at least a 7 coach train end to end. That plan is only a rough example of the final layout. I do want to be able to run trains straight through as well though. Not just have to stop them all. 

[thatmanmongo]

So would I just isolate each end of the diagonal?

[thatmanmongo]

Will I need 2 modules as well or could they be wired into the same one?

[Crosland]

If you can guarantee that there will never be a train on both diagonals at the same time causing conflicting polarity requirements (i.e. entering/leaving/running in opposite directions) then you could use a single module.

 

I would use a module for each diagonal.

 

Andrew

[Phil S]

If you wish to avoid the dcc-module option - which detects a momentary short on either rail at the gap (if the polarity is wrong) > causing an immediate changeover to correct the problem; consider the following:

 

On each track, and at each end: a beam break optical/infra-red detectors with 2 beams (easily available as kits from Maplin etc) :  2 beams but only 1 'module' needed at each end - inside and outside of the gap.

As a train approaches 'the gap' from inside or outside - it breaks the 'first' beam break, and this is used to switch the track to its correct polarity for that end.   As it passes the gap, the 2nd beam break is also broken, but has no further effect, as the change has already been made.

Then as it approaches the opposite end, the process is copied by the bean break detector at that end, with its 2 beams

 

if you don't like the idea of optical beam breaks, and still wish to avoid the momentary-short [ particularly in the larger scales such as G - with possibly 10A currents ] the same result can be achieved by 4 small electrically isolated lengths of track - and detecting current flow approaching one end or the other, to PRESET the polarity before the train reaches the either gap.