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Author Topic: Reverse loop  (Read 435 times)

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Offline barneyadi

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Reverse loop
« on: March 13, 2018, 05:51:58 PM »
Hi

Currently working on a track plan which has a reverse loop and wondering how to deal with this in DCC. If it helps after the point where the track starts and comes back too there will be points to make a fiddle yard if that helps or changes things.

Online njee20

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Re: Reverse loop
« Reply #1 on: March 13, 2018, 05:54:18 PM »
Cheapest is a manual switch to throw. Easiest is an auto reversing module.

Don’t get Digitrax AR1s, I was disappointed with mine. Plenty of other options.

Offline barneyadi

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Re: Reverse loop
« Reply #2 on: March 13, 2018, 08:10:22 PM »
Any auto reversing modules you would recommend? How easy are they to wire and use?

Offline colpatben

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Re: Reverse loop
« Reply #3 on: March 13, 2018, 09:08:17 PM »
Any auto reversing modules you would recommend? How easy are they to wire and use?
Tam Valley dual frog juicer, two wires in from DCC bus and two wires out to fully isolated reversing loop. Fit and forget.
Only for DCC, you cannot use on DC.
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Online njee20

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Re: Reverse loop
« Reply #4 on: March 13, 2018, 09:56:44 PM »
Yes, the Tam Valley sprung to mind. I actually now use Hornby ones which were mega cheap on clearance from Hattons. They're fine, not sure they still do them, hence not recommending them.

Offline colpatben

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Re: Reverse loop
« Reply #5 on: March 14, 2018, 05:50:12 AM »
Yes, the Tam Valley sprung to mind. I actually now use Hornby ones which were mega cheap on clearance from Hattons. They're fine, not sure they still do them, hence not recommending them.
Hornby R8239 but you can only find the odd one but not at a good price so overkill in this case.

I generally say that a Tam Valley frog juicer is approx £12.50 per output.
Mono for single Turnout frog @ £12.30
Dual (2 outputs) for facing Turnouts or in the OPs case a reversing loop @ £26.45. Need to set a jumper on the board.
Hex (6 outputs) for multipule Turnouts or three reversing loops @ £69.60.

All from Digitrains at todays prices.

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Online njee20

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Re: Reverse loop
« Reply #6 on: March 14, 2018, 09:20:59 AM »
No, it was the Hornby R8328, 8329 is the booster. They appear to still be available but are £40 each, I bought them at £12 each, definitely wouldn't pay £40.

The Dual Frog juicer has the advantage of being solid state (I believe) rather than using relays. Relay based controllers, like the AR1 or R8328 are a bit blunt force and rely on beating the cut out from the DCC system. I had two AR1s, one was faulty out of the box, the other suddenly stopped working after about a year.

Offline Steven B

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Re: Reverse loop
« Reply #7 on: March 14, 2018, 09:26:50 AM »
A pair of SPDT microswitches connected to the tie-bar of the point will cost less than a fiver.



Steven B.

Offline Dalek

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Re: Reverse loop
« Reply #8 on: March 14, 2018, 01:06:13 PM »
How does a reverse loop operate in practise ?

Can you run the loco in, change the point while keeping it running all the way round or do you need to stop, flick a switch or use one of the above devices to take care or the polarity switch ?

Offline ntpntpntp

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Re: Reverse loop
« Reply #9 on: March 14, 2018, 01:40:10 PM »
How does a reverse loop operate in practise ?

Can you run the loco in, change the point while keeping it running all the way round or do you need to stop, flick a switch or use one of the above devices to take care or the polarity switch ?

Basically the polarity of the loop section has to match as the loco enters the loop, so that's either by flicking a manual switch (which can be tied to the point direction) or letting a reverse loop module detect the mismatch and rapidly flip the polarity.  Then the polarity of the loop then has to flip again before (or as) the loco exits the loop, again by use of the manual switch or the reverse loop module.

The great thing with DCC is you can flip the polarity and the loco will continue in the same direction (unlike DC).  If you use one of the rapidly acting electronic units then the loco doesn't notice the momentary loss of power - although preferably you need some sort of "keep-alive" in the decoder to be absolutely sure of this.

Personally I have a bit of a "thing" against reverse loop modules and frog juicers which work by detecting the short circuit:  I would much rather the trigger to swap polarity be something external to the process such as a train sensor, and frogs changed by a switch. This is because my DCC experience is mostly from the garden railway world where we can have several amps available!
« Last Edit: March 14, 2018, 01:49:20 PM by ntpntpntp »
Nick.   2016 celebrating the 20th anniversary of "Königshafen" exhibition layout!

Offline barneyadi

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Re: Reverse loop
« Reply #10 on: March 14, 2018, 03:06:34 PM »
So this is a picture of my reverse loop. How would i set up the wiring for solutions already mentioned?



Any help much appreciated.

Offline ntpntpntp

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Re: Reverse loop
« Reply #11 on: March 14, 2018, 04:22:44 PM »
Double insulate (both rails) on both routes out of the rightmost point which is forming the neck of the reverse loop. so that's 4 isolating joiners.  All those passing loops are within the reverse loop section. 



Alternatively you could move two isolating joiners up beyond the toe of the left hand point of your passing loops. The effect is the same, but if perhaps you'll be shunting a loco at either end of the passing loops then it might be better to keep those loops and a short length of plain track at the left end of the passing loops outside of the reverse loop section.



The important thing is to keep the reverse loop section long enough to hold a complete train - what you can't have is the loco exiting one end of the switched section while wagons with metal wheels are still entering, as this will drive any reversing module nuts!

The power feed from your system (the "to main" trackwork to the right of the loop) goes into the reversing unit or DPDT switch, the switched output of the reversing module or DPDT switch feeds the trackwork within the loop.  Simples.


« Last Edit: March 14, 2018, 11:50:23 PM by ntpntpntp »
Nick.   2016 celebrating the 20th anniversary of "Königshafen" exhibition layout!

 

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