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DCC Auto Reverse on Loop


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I'm adding a loop to my DCC tramway. I will need to add a revising module.  I am wondering how long to make the section of track that the module will control.  General advice is longer than the longest "train". But tram movements are different to standard train movements. The section could be anything from 20 cm to the full 2 meters of the loop. Has anyone got any experience or thoughts? 

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I'm adding a loop to my DCC tramway. I will need to add a revising module.  I am wondering how long to make the section of track that the module will control.  General advice is longer than the longest "train". But tram movements are different to standard train movements. The section could be anything from 20 cm to the full 2 meters of the loop. Has anyone got any experience or thoughts? 

If your trams collect from the overhead line through the trolley pole, or pantograph if that's what your trams have, AND use BOTH rails as the common return, then you don't need a reversing module.

 

However, if you collect from the track in the conventional 2 rail way, then you do.

 

The main difference that I can think of is that you may have several trams in the loop at once, no problem there. But you may well have problems if you have a tram entering one end of the loop at the same time as you have another tram leaving as both trams would end up bridging opposite ends of the loop simultaneously which would cause a short no matter which polarity the autoreverser was switched to. 

 

So all you need to do is have a short autoreverse section, probably best at the entrance to the loop, that can accommodate only 1 tram at a time, and that you never stop a tram in that section, but let it run through the autoreverse section and then bring it to a halt in the queue to leave the loop itself.

 

A general word of advice on reversing modules, make sure that you get one that works faster than your DCC command station, or your command station may sense the short and shut down its track output before the autoreverse module has had an opportunity to reverse the polarity. So try to avoid the older designs that use electromagnetic relay to do the switching and use one that use solid state electronics instead. Look in the DCC section of the forum for advice on which autoreverse modules work best with which DCC command stations, or ask one of the moderators to move this topic to the DCC question section of the forum.

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Thanks for the reply Keith.

 

I'm not using live overhead, thus the loop being an issue.  You've identified the issues that have been concerning me with regard to tram multiple trams on the loop.  I like your reasoning for a shot section, I think that should be safer. I will have to place it carefully. I plan to have a tram stop on the loop, if I place a short auto-reversing section after the stop I shouldn't have a problem with trams entering and leaving at the same time.

 

I'll look into the compatibility issue you mentioned. Thanks for the tip.

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  • 2 years later...

I attached the DCC reversing module to short length of track alnd it worked well.

 

Then a friend bought his Blackpool Flexity round and it is about three times the length of the section with the module, so we couldn't run it. I rewired, adding DPDT switch to the feed to the next section of track so it can be fed from the normal track supply of the from the reversing module. I can now have a short or a long section connected to the Auto Reversing Module. It's a good solution.

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  • 3 weeks later...

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