Reverse loop question - is this possible?

[TomJ]

Not sure if what I am trying to achieve is actually possible!! On my double track oval I have a reverse loop to get trains back to the terminus. Hopefully this picture demonstrate this 

 

 

So I was planning to wire it up like this - using a double frog juicer which I’m pretty sure would work 

 

 

But then I wondered if I could use the empty space top left for a bit of a yard or engine shed. And if so how would I wire it - and indeed could it be done?

 

 

Do I need another juicer below the point? How do I wire the yard to keep all the tracks live and stop my sound fitted locos going quiet? 

 

Am I asking too much of DCC??

 

Many thanks 

[F-UnitMad]

Looks to me like you actually have TWO reverse loops in fact.

No idea how to wire them though, sorry.

[jpendle]

Two frog juicers will work without issue for a reverse loop, that's what I did on my previous layout.

I would recommend a solid state juicer, such as the one's from Tam Valley, rather than a relay based one, such as the Gaugemaster Autofrog. Solid state juicers are much faster.

 

As regards the yard, it depends. Remember that the reverse section with the juicers has to be as long as your longest train, so that rolling stock with pickups don't cause problems.

 

So IF your longest train will fit in either section from the point to the main layout then you just need one juicer in that section, if you trains won't fit then you'll need to have a re-think about how the yard is arranged.

 

Regards,

 

John P

[jpendle]

4 minutes ago, F-UnitMad said:

Looks to me like you actually have TWO reverse loops in fact.

No idea how to wire them though, sorry.

The top diagram just has one reverse loop. If you remove the track crossing from bottom left tp top right you are left with a double track line running through two station areas, plus what looks like lower level storage sidings.

 

Regards,

 

John P

[Grovenor]

You don't want a frog juicer for this, you want a reverse loop module. You only need the one reverse loop module, any sidings connected to the reversing section will just reverse along with it, which is not a concern.

But equally you could connect the sidings to the top section of the main oval.

[TomJ]

I must confess to not really understanding the difference between using a frog juicer or a reverse module! What is the difference and which one do I want?? The main criteria is I don’t want to have to stop trains but allow them too run through

 

Would either of these work?

 

[jpendle]

2 hours ago, Grovenor said:

You don't want a frog juicer for this, you want a reverse loop module. You only need the one reverse loop module, any sidings connected to the reversing section will just reverse along with it, which is not a concern.

But equally you could connect the sidings to the top section of the main oval.

They are effectively the same thing, 2 frog juicers = 1 reverse loop module.

Both detect short circuits as the loco enters either the reverse lop or the frog and then switch the track polarity as needed.

Because a reverse loop module changes the polarity on 2 tracks at a time you wouldn't want to use it as a frog juicer, but because frog juicers only deal with one track there's nothing stopping you using 2 of them for a reverse loop module.

 

I used a Tam Valley 6 way Frog Juicer on my last layout to switch polarity on the 4 frogs of 2 crossovers, I used the last 2 outputs to deal with the reverse loop.

 

1 hour ago, TomJ said:

Would either of these work?

Yes the first one with the point NOT in the reverse loop.

 

Regards,

 

John P

[TomJ]

Thanks so much. Really appreciated 

[RobinofLoxley]

3 hours ago, jpendle said:

The top diagram just has one reverse loop. If you remove the track crossing from bottom left tp top right you are left with a double track line running through two station areas, plus what looks like lower level storage sidings.

 

Regards,

 

John P

There are surely two reverse loops, but the line that crosses the centre of the layout is common to both, so provided the polarity of that track section is changed at the right time, and that will depend on the position of the turnouts at each end of that section, there won't be any issue.

 

If you are happy that you understand the electrics well enough to use frog juicers then do; personally if I wanted to change track polarity I would use the device dedicated for the purpose, namely a reversing module.

[franciswilliamwebb]

2 minutes ago, RobinofLoxley said:

If you are happy that you understand the electrics well enough to use frog juicers then do; personally if I wanted to change track polarity I would use the device dedicated for the purpose, namely a reversing module.

 

A frog juicer IS a device to change track polarity, simple.  Certainly my go-to device for reverse loops.

[F-UnitMad]

2 hours ago, RobinofLoxley said:

There are surely two reverse loops, but the line that crosses the centre of the layout is common to both

Thankyou, that's what I meant. It might only be intended for use in one direction, but there are two routes for potential use as reverse loops.

[jpendle]

2 hours ago, RobinofLoxley said:

There are surely two reverse loops, but the line that crosses the centre of the layout is common to both

Perhaps a better term would be a reversing section. There's only one, but it can be used in either direction.

 

Regards,

 

John P

[jpendle]

2 hours ago, RobinofLoxley said:

 so provided the polarity of that track section is changed at the right time, and that will depend on the position of the turnouts at each end of that section, there won't be any issue.

The polarity of the track in the reversing section has nothing to do with the position of the points at either end. The reversing section must be electrically  isolated from the rest of the layout, its polarity is controlled by the frog juicers/reverse loop module and nothing else.

The polarity of the reverse section will change when a loco either enters or leaves the reversing section.

 

Regards,

 

John P

[RobinofLoxley]

Of course you are right i had a complete brain fade moment there

 

[Grovenor]

19 hours ago, franciswilliamwebb said:

 

A frog juicer IS a device to change track polarity, simple.  Certainly my go-to device for reverse loops.

A frog juicer IS a device to change frog polarity.  You should make it clear that "A frog juicer" will not do a reversing section, you need to use two of them. Reverse loop modules are designed for the job. Unless you already have spare frog juicers then might as well buy the right thing.

[franciswilliamwebb]

17 minutes ago, Grovenor said:

You should make it clear that "A frog juicer" will not do a reversing section, you need to use two of them. Reverse loop modules are designed for the job. Unless you already have spare frog juicers then might as well buy the right thing.

 

No.  There is a range of frog juicers.  For example a Hex Frog Juicer will do 3 reverse loops and is designed and documented for this.  The original poster specified a double Frog Juicer, so presumably is well up to speed.

 

I'm not going to replace my Hex unit with three reverse loop modules, I'll stick with the right thing thanks.  I didn't have spare reverse loop modules when I bought it😉

[Grovenor]

Why say "No" and then carry on to agree with me? It seems we agree that a reverse loop needs two frog juicers, and you had spares so used them. Granted the OP did say two frog juicers in his opening post but its not clear that he already has them.

No one has suggested you should change what you have, this topic was about answering the OP's question.

[TomJ]

Sorry - I should have been clearer! I did indeed mean a dual frog juicer - one output for each rail. I went with juicers because I’ve used them before for point frogs so stuck with what I knew!

 

What I wasn’t so sure was where to put it or even whether I need two dual juicers

 

Thanks to everyone for the advice. I’ll try to wire it up this evening and I’ll let you know how I get on. You may hear the swearing on here!! 

[5BarVT]

1 hour ago, TomJ said:

Sorry - I should have been clearer! I did indeed mean a dual frog juicer - one output for each rail. I went with juicers because I’ve used them before for point frogs so stuck with what I knew!

 

What I wasn’t so sure was where to put it or even whether I need two dual juicers

 

Thanks to everyone for the advice. I’ll try to wire it up this evening and I’ll let you know how I get on. You may hear the swearing on here!! 

If you have the extra sidings within the reversing section, you need to make sure that you never (even inadvertently) have a train coming into the section from both ends at the same time.  (Also applies without points in there but much less likely to happen as it’s “obvious” there is nowhere to go.)

If you shorten the section to keep the points out of it then train length becomes an issue.  If your only vehicles with power connections to the wheels are locos then you might get away with it, but metal wheels running through joints could still touch both together.  If you have coach lighting etc you could end up with the loco at the front bridging one gap and a lighting compatible coach (even if not fitted with lights) bridging the other.

My inclination would be to go for the longer section and manage the two trains issue.

Paul.

[Steven B]

On 10/03/2024 at 17:20, TomJ said:

Would either of these work?

 

 

Both will work - I'd opt for the second one (i.e. power the yard via the dual-juicer/auto-reverser. Remember the reversing section needs to be big enough to fit a complete train in.

 

Steven B

[F-UnitMad]

9 hours ago, 5BarVT said:

If you have coach lighting etc you could end up with the loco at the front bridging one gap and a lighting compatible coach (even if not fitted with lights) bridging the other.

Indeed, metal wheels will trigger a frog juicer, regardless of if they're on a loco or rolling stock.

[Andymsa]

Sorry to be nit picky but with dcc there is no such thing as polarity. The correct term should be phase as each rail is opposite in phase to each other.