Reverse Loop

[JamesP]

Thanks for the details!  My understanding (and I confess, it is very limited with AF) is that the 695 is supposed to reverse the polarity automatically when wired into a turnout.  I believe the turnout supplies the proper polarity to the inside rails of the loop, while the 695 supplies the proper polarity to the outside rail of the loop.  Throwing the turnout is supposed to activate the 695, causing it to connect the outside rail to the proper rail of the mainline... a very slick way to do it!  So, it sounds like the 695 isn't operating when the turnout is thrown.  The first step - as always - is to go over the wiring with a fine tooth comb.  This is a link to the 695 instructions:  http://www.tuveson.com/965reverseLooprelay/965instructions.htm

If the wiring is correct, then the 695 may be malfunctioning... however, I'll have to leave that up to the Flyer experts... never had one apart.  It is also possible that the turnout also has an internal problem, and isn't activating the 695.  At any rate, double check the wiring, and hopefully some guys with more AF experience can give us some tips!

 - James

[flyer newbie]

I'm using the American Flyer 695 Reverse Relay Loop to wire a simple reverse loop.  When the train approaches the switch, it stops at the fiber pin.  When I flip the switch on the 695 Relay, the train will continue.  When it approches the switch again at the end of the loop, I have to throw the switch again on the 695 Relay.  The relay is supposed to change the polarity automatically but it doesn't seem to be working correctly and I cannot figure out the problem.  In short, the train stops at the fiber pins at both portions of the reverse loop until I manually flip a lever on the bottom of the 695 Relay. 

Thanks for your assistance.

[JamesP]

2 rail reverse loops are wired the same regardless of AC or DC power...what kind of problem are you having?  A classic, simple reverse loop is set up so that the two rails of the loop (ar at least a good portion of it) are isolated from the turnout and mainline.  The transformer is wired directly to the isolated track, and the mainline is fed from the transformer through a double-throw, double-pole (DPDT) switch that is wired as a polarity reversing switch.  When the train passes from the mainline through the turnout into the isolated reverse loop section, the DPDT polarity reversing switch is flipped so that the mainline polarity is reversed, matching the mainline to the other end of the reverse loop.  By reversing the mainline polarity instead of the loop, you can run the train without stopping it in the loop itself.

For a simple diagram, take a look at this picture from about.com :

http://0.tqn.com/d/modeltrains/1/0/h/6/-/-/reverse-loop-wiring-schematic.JPG

(EDIT: This picture shows the DPDT switch going to the reverse loop.  I would wire it to the mainline instead, so trains don't have to stop in the reverse loop)

And this is a drawing from NMRA.org of the reversing DPDT switch:

http://www.nmra.org/beginner/images/reverse.gif

Of course, there are more than one way to skin a cat; so there are other methods using a bridge rectifier instead, but that wouldn't work right with AC.  For DCC there are reversing modules that do the work of the DPDT switch automatically. 

Give us more details of the problem, and one of us can hopefully help you out!

 - James

[flyer newbie]

Nope.  Talking about American Flyer 2 rail.

[gunrunnerjohn]

Well, for O-gauge it's just lay the track.  Are you talking about HO?

[flyer newbie]

Any reverse loop experts out there?