Model Railway Forum banner
1 - 3 of 3 Posts

·
Just another modeller
Joined
·
9,983 Posts
You will need a reverse loop module if any track doubhles back on itself - the simplest form of that is a single track teardrop shaped loop that the loco enters one way and leaves over the same point in the opposite directon on the single track. A diagonal across a loop has the same sort of problem. If you have any form of reverse loop it creates a short circuit in the track so the special device is needed.

If you draw both rails in a teardrop loop and trace each rail you will see what I mean....

Richard
 

·
Just another modeller
Joined
·
9,983 Posts
*** Edwin has explained it well I think.

When you buy an autoreverser, avoid ANY which use a relay - that includes lenz, Digitrax and MRC or Gaugemaster... - they are simply too slow to react in some circumstances, often "chattering" as relay based products can and eventually, the relay always fails.

You need one that is totally solid state/electronic to get best reliability and these are readily available, often for less money too. The OG-AR from DCCspecialties in USA is a very good choice as it also has inbuilt overload protection.

I think John at bromsgrove models stocks these in the UK

Regards

Richard
 

·
Just another modeller
Joined
·
9,983 Posts
QUOTE (noiseboy @ 15 Dec 2008, 18:00) <{POST_SNAPBACK}>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!

*** A specific answer to part of this (athough Edwin covered most of it well).

But... its important to really understand the basics, and each explaination helps many others who haven't yet asked the question - so....

What happens and why does the section need to be at the very least full train long?

As the wheels touch the gap, the circuitry will change the polarity of the reversing loop section the train is in and leaving to match the section of track it is entering. It will do this in about 1/10,000th of a second with an electronic reverser, so you see no reaction... it just happens.

If the section is short and the train spans entry section, rev loop section and exit section, then its clearly impossible for all 3 to be at the same polarity.

The conflict will very likely cause a short which may be repeated every time metal wheels at each end of the loop pass the gaps... clearly not something desirable!

Richard
 
1 - 3 of 3 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top