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Model Railway Double Reverse Loop Wiring
How to wire two reverse loops on your two-rail layout for automatic operation
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Here we show you how to wire the reverse loops and track switches on a double-loop layout with a single connecting main line. Wiring a reversing loop (or turn-around track) may seem complicated, but if you take one step at a time and check your work, you will have a fully automated reverse loop and worry-free train operation.
[Click here to review reverse loop fundamentals]
This plan is for a 'dog bone' type layout with a single track main line: It is completely automated, with automatic control of the track polarity and the track switches (or 'turnouts').
This system is an economical choice for:
- DCC layouts
- DC or AC layouts with single cab control (one train power pack or transformer)
Double reverse loop control for DC, DCC or AC layouts.
This system, shown above, uses a DPDT relay to control polarity of the main line.
The switch machines operate simultaneously, controlled by
the D2T-2W or D2T-3W dual IR train detector.
When the track switches are lined for the tracks marked 'M' the relay is 'off.' The main line polarity
will match the loop polarity at points marked 'M', allowing trains to cross at those locations.
• Click here to learn how a relay works. [pdf]
When the track switches are lined for the tracks marked 'X' the relay is 'on.'
The main line polarity will match the loop polarity at points 'X', allowing trains to cross there.
Wire the switch machines so the switch points are lined with the 'M' junctions
when sensor 1 is triggered. If the points line the wrong way, swap the connections to the switch machine.
How it works: Assume a train is moving left-to-right on the main track, approaching the
east loop, and the turnout is lined with 'M'.
The train enters the east loop and travels counter-clockwise. When it triggers sensor 2,
the D2T-2W (or -3W) will throw both switches to line with 'X' and will turn on the relay.
The main line and loop track polarities will now match at the two 'X' locations.
The train returns to the main line.
Now the train approaches the west loop, moving right-to-left. The switch points are still lined
to the 'X' junctions and the track polarities still match there.
The train travels counter-clockwise around the west loop and triggers sensor 1.
The D2T-2W (or -3W) throws both switches to line with the 'M' junctions
and turns off the relay. Mainline and loop track polarities now match at points 'M'
and the train returns to the main line.
Manual control of the switches is possible, as shown in the
D2T-2W installation guide and the D2T-3W installation guide.
For AC single cab and DCC powered layouts, this is all you need.
On DC layouts, manually changing the turnout positions will cause a train on the
main track to change direction. If you choose to manually control the turnouts, first stop the train if it is on the main track!
D2T-2W turnout control for 2-wire switch machines
Two-wire switch machines include single-coil 'snap' switches such as Kato™, LGB™ and Aristocraft™
as well as slow motion switch machines such as
Tortoise™, Cobalt Classic™ and SwitchMaster™
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D2T-3W turnout control for 3-wire switch machines
Three-wire switch machines, also known as twin-coil or dual-solenoid switch machines, include Atlas™, Bachmann™, Kemtron™, Peco™ and American Flyer™.
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MRAPR-12v DPDT relay
coil voltage 10 - 17v AC or DC
contacts rated for up to 8 amps
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[ Choose a different type of reversing track ]
© copyright 2009-2022 Azatrax LLC, Longmont, Colorado
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