Reversing Loop

[LGB-Sid]

Probably been asked a few times, After running outside decided I don't like the look of the long double lines in the middle of my layout, so am thinking of replacing them with a single line and a Massoth reversing loop module 8157001 as originally intended, also uses a lot less track to travel the distance needed to get the left hand loop into it's final place

I assume this can be done with one module where the two end's are powered the same polarity and the center single line polarity is switched ?

If a train was parked in the siding in the middle of the long straight I assume this would have no effect on it as other train enters the main single line and the polarity switches ?

Center line is 9m Long so long enough for any train I will ever run, I assume the track breaks would go after the points at each end in the actual loops ?

The siding in the middle is a station with a building so a good place to hide / protect the reversing module and then the wiring is about the same distance to each loop

Center single line and siding on image below is not to scale.

Out of curiosity if a train enters the long straight from the left and you forget about it and set one off that enters from the Right what happens when the second train enters ? I know what would happen if they meet head on

Track is DCC powered

 

[LGB-Sid]

Think I just worked out this doesn't work, I need to reverse the loops not the line that joins them together. Can one module reverse two loops or does it need two ?

 

[Gizzy]

If you are using one train in any loop at any one time, then a reversing module will work fine for both loops....

 

[dunnyrail]

So long as Trains are not attempting to change the revercing section simultaniously then no problems will occur. Indeed if one is already on the section and another attempts to join it I think there may not be problems but I am not sure of this. However it would be sloppy Operation to attempt that and Signals could be arranged to reflect the situation with some clever wiring. However what I believe happens is that the reverce Module changes the Polarity (not quite the right term with DCC) while a Train is running over the joint so that a Short does not occur. Once a Train is on the section with DCC it does not care what way round the power is picked up from as the Chip just wants DCC and the Motor is getting its DC to tell it which way to run from the Chip.

So if the section is long enough any amount of Trains could be running on it, what you do not want to be attempting is to try to be changing things at both ends of the section with a very long metal wheeled or more than one train.
JonD

 

[Gavin Sowry]

I could wire those reverse loops for less than ten quid.

 

[Deleted member 1986]

The first diagram shows a train (green arrow) entering a two-rail reverse loop. The insulated rail joints are necessary because without them, electricity would flow from one side of the power pack, around the loop and directly back to the other side of the power pack. This would be a short circuit and would prevent the train from getting power. It would also pop the circuit breaker in the power pack.

The reason for two sets of insulated rail joints and the two sets of electrical connections to the power pack will be shown in the next two figures.



The train travels around the loop and is approaching the exit, ready to rejoin the main line.

But there will be a problem when the train attempts to cross the insulated rail joints where the loop meets the main line.

The metal wheels of the locomotive will bridge the insulated joints, creating short circuits. Electricity from one side of the power pack will be able to return directly to the other side of the power pack. The train will not receive power, and the circuit breaker in the power pack will trip.


The solution is to swap the power pack connections at the main track before the train leaves the loop. This is done with a DPDT (double pole, double throw) toggle switch or relay as shown in the third figure.

For layouts that are powered by DCC power supplies, you have the option of swapping the power connections to the loop instead of the main line. All that matters is that the power connections match at the insulated joints where the train is ready to cross.

On layouts with DC power, the track power connections must be swapped on the track that is not occupied by the train. On DC layouts, the track polarity (which rail is positive or negative) determines the direction of train travel. If we changed the polarity of the loop power while the train is in the loop, the train would suddenly change direction. Therefore we must change the main track polarity while the train is on the loop track.
As you can see, every time a train travels around the reversing loop, the track polarity must be changed and the track switch must be set. If left to manual control, these are two opportunities for error.





8175001
DiMAX Reverse Loop Module

No Short Circuits!

The DiMAX Reverse Loop Module is a high performance unit which is able to handle digital track currents up to 15 AMPS without causing a short circuit.
Conventional units cause short term, short circuits when the train enters the loop to trigger a change in the polarity of the track voltage.
The new DiMAX Reverse Loop Module avoids just that. The deliberate overload of the Digital Central Station by this method does not exist anymore. The DiMAX Reverse Loop Module extends the lifespan of all components involved considerably.

The DiMAX Reverse Loop Module works with all NMRA/DCC compatible digital systems and depending on the voltage used, handles up to 15 Amps. Current consumption like this can easily be reached with multiple motored G-Scale locomotives or consists of multiple locomotives.
The DiMAX Reverse Loop Module may be used in the regular short circuit mode as well.

The set includes 8 insulated track connectors and 4 sensing track units.

 

[Gavin Sowry]

The set includes 8 insulated track connectors and 4 sensing track units.

How much of Her Majesty's coin will it cost me?

I actually have two loops wired as you have explained. In order to overcome the perceived 'problems' that you mentioned, I have introduced an operating discipline.... the DPDT switch is close by the hand operated turnout, my rule.... the switch must always lay the same way as the points are set. Yes, you do have to stop the train, and reverse the polarity, and switch. But just like in real life these days, (in a back to the future sense) the train has to stop so the crew can get out and set the road.

 

[Deleted member 1986]

I actually have two loops wired as you have explained. In order to overcome the perceived 'problems' that you mentioned, I have introduced an operating discipline.... the DPDT switch is close by the hand operated turnout, my rule.... the switch must always lay the same way as the points are set. Yes, you do have to stop the train, and reverse the polarity, and switch. But just like in real life these days, (in a back to the future sense) the train has to stop so the crew can get out and set the road.

As mentioned above that was exactly the same principle that was used on my two loops, from time to time "Murphy's Law" kicked in when visitors were operating the line!

Plus in my own mind seemed somewhat an archaic method when operating under DCC, having to use a manual switch, and deliberately inducing a short circuit hence the change over to the Massoth Modules.......

How much of Her Majesty's coin will it cost me? Around £70.00 see advert for GRO, small price to pay to prevent wheel and track pitting, avoiding excessive tripping of the CS, also being able to lower the trip time from the factory set 4.5ms to 1ms, as ever you pays your coin, takes your choice..........................

 

[LGB-Sid]

Thanks for the reply's, so in theory One Massoth reversing loop module would do both loops...but only one train in one loop at any one time, if you run two trains they both can not enter the individual loops at the same time ? if that's the case Sod's law says use too modules then I assume, as I am bound to end up with one train in one loop and another enters the second loop. I know it might seem odd to remove a double line and add reversing loops but two 9m long dead straight lines in a narrow area look very boring and very main lineish to me rather than a narrow / heritage line look.

 

[stockers]

Can you change the elevation of one of the long straights Sid, or add a bit of curvature.

 

[LGB-Sid]

Can you change the elevation of one of the long straights Sid, or add a bit of curvature.

The two lines are heading to an area behind a shed where they join in a loop out of that loop comes a third line that climbs and runs parallel to the original two for a short while until it's high enough to cross over them heading to my proposed land grab so will struggle to elevate one of them. hence the idea of getting rid of one of them the border they run in is only about 600mm deep not really deep enough to move one too the back and hide it with plants which was the other idea I had. considering the size of my garden I started building my line in the wrong place, but you live and learn

 

[LGB-Sid]

DiMAX Reverse Loop Module came today in the packet is 4 diodes ? what are they for,. The instructions say cable size for the Main track and Return loop should be 1.2 / 2mm sq not a problem but I assume I don't need cables that size for the sensor rails as I have a roll of twin .5mm sq that I could use for them. Final question anybody in the UK installed one of these in a waterproof junction box outside ? are they happy in a small enclosed plastic box all year round ? the Garden shed is too far away for it, and SWMBO won't be happy with more holes in he house walls with wires poking through them with my trains electrical bits attached on the end of them

 

[stockers]

I don't have the reversing loop unit Sid but my digital point controllers live out all year. been out since 2009 with no problems. I place them on a block of wood to lift them out of any water and cover them with a resin building - a line side shed. Plenty of air to let them vent - I don't even fill in the windows.

 

[Paul M]

DiMAX Reverse Loop Module came today in the packet is 4 diodes ? what are they for,. The instructions say cable size for the Main track and Return loop should be 1.2 / 2mm sq not a problem but I assume I don't need cables that size for the sensor rails as I have a roll of twin .5mm sq that I could use for them. Final question anybody in the UK installed one of these in a waterproof junction box outside ? are they happy in a small enclosed plastic box all year round ? the Garden shed is too far away for it, and SWMBO won't be happy with more holes in he house walls with wires poking through them with my trains electrical bits attached on the end of them

Sid, the idea of putting the wires etc in a plastic box is sound. All you need to do is check the IP rating (ingress protection) the first figure is solids & the second is liquid. Anything over 4 on the second figure is fine.

 

[stockers]

The problem with a waterproof box is that they rarely actually are. A small hole drilled to let any water drain out the base is a good idea. A totally secure box would probably sweat and create condensation anyway - not good for electronics. Interesting that many IPXX boxes now have a provision for drilling said hole.

 

[Rhinochugger]

The problem with a waterproof box is that they rarely actually are. A small hole drilled to let any water drain out the base is a good idea. A totally secure box would probably sweat and create condensation anyway - not good for electronics. Interesting that many IPXX boxes now have a provision for drilling said hole.

The alternative is to use IP65 boxes, and ensure that they are totally sealed i.e. use the eternal clip fixing bracket and don't drill holes in the back of the box if it starts dry, there's nothing there to sweat - the minuscule quantity of air is unlikely to cause that much moisture.

You have also got to make sure that the cable glands are the correct size.

Surprising, in a way, that it has taken this long to get totally sealed boxes

(Or I see that Screwfix now sell one with external fixing lugs)

The switch box under the water tower is a sealed box which I bought with the switches ready installed on evilbay when I first built the WWSR about 10 years ago. When I moved up here, and was ready to re-install it, I opened up the box to check inside - perfick, as new

 

[LGB-Sid]

Thanks for the reply's, I was going to put it in a water tower but I still haven't made one yet Was just curious about so called IP waterproof boxes I do have a couple that have pond bits connected to them but when you look inside it is obvious that moisture does get in to them as the terminals are corroded.

 

[Paul M]

Thanks for the repy's, I was going to put it in a water tower but I still haven't made one yet Was just curious about so called IP waterproof boxes I do have a couple that have pond bits connected to them but when you look inside it is obvious that moisture does get in to them as the terminals are corroded.

Putting any water proof box in a water tower is asking for trouble! Wouldn't it be better to put it underneath?

 

[Rhinochugger]

Thanks for the reply's, I was going to put it in a water tower but I still haven't made one yet Was just curious about so called IP waterproof boxes I do have a couple that have pond bits connected to them but when you look inside it is obvious that moisture does get in to them as the terminals are corroded.

I suspect the cable gland may not be the correct size - get it right, as did the bloke who built my switch box, and it'll last cables exit from the box straight down into the ground (but of course are properly sealed with glands - none of this silicone rubbish)

 

[LGB-Sid]

Putting any water proof box in a water tower is asking for trouble! Wouldn't it be better to put it underneath?

It's not a real water tower , doesn't contain any water it's just a model of a water tower to fill up steam engines