Metal Wheels & Reversing Loops / Wye junctions

Ralphmp

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Doing some more layout expansion with a "wye" junction (see attached logical diagram - not to scale!).

RevLoopandWye.jpg

I plan to use Massoth reverse loop modules and, whilst I'm ok with the wiring, I just want to check my understanding of the impact of using metal wheels on rolling stock. This is -
  • If I have a loco pulling coaches and/or wagons that have metal wheels but are not electrically connected to either each other or the loco, then as long as the legs of the Wye and the reversing loop itself are long enough to can accommodate the loco, then no issue. This is true for both single motor (e.g. Stainz) and double motor (e.g. Mallet) locos.
  • If the metal-wheeled wagons / coaches are electrically connected to the loco - e.g. for lighting purposes - or I have an interconnected set - e.g. an RhB 3-coach Allegra set - then the legs of the Wye and the reversing loop must be large enough to contain all of the interconnected loco/wagons/coaches.
Hopefully the above is correct as it seems logical.

However, if I have wagons/coaches with metal wheels drawing power from the track (e.g. lighting purposes) but which aren't connected to each other or to a loco, am I also right in thinking that the legs of the Wye and the reversing loop itself only need to be long enough to hold either the loco or the longest coach?

Sorry for what probably seems a dumb question but I don't want to lay track & wire in the reversing loop modules only to find I've created something which can't be used by some of my locos / rolling stock.

Thanks in advance
 
Hi Phil,

You can get away using one reversing loop module if your longest train will fin in the track between the section breaks. The module will only need to switch the single track section between the wye and the loop. The loop keeps the same polarity as the main layout.
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RevLoopandWye.jpg
 
A thought regarding the question of metal wheeled stock. Even if metal wheels aren't electrically connected to each other they can cause a brief short when traversing a rail gap with opposite polarities each side of the gap. One way to avoid this is to arrange two rail breaks within a few millimeters of each other. The short length of rail between the two gaps isn't connected to the power at all.
 
Mark

I was planning to use single channel decoders for the points controlling the reversing loop and the points on the right hand side of the "Wye" (the point closest to the reversing loop in the diagram).

To avoid any issues, I'm planning to take the power for these from track inside the main layout - i.e. somewhere before the bottom Wye point and above the top Wye point in the diagram.

My thinking is that this would avoid any issues with the feed to the decoders swapping polarity from +ve to -ve, as might be the case if I located the decoders next to their respective points. Does this sound OK?

Thanks
Phil
 
A thought regarding the question of metal wheeled stock. Even if metal wheels aren't electrically connected to each other they can cause a brief short when traversing a rail gap with opposite polarities each side of the gap. One way to avoid this is to arrange two rail breaks within a few millimeters of each other. The short length of rail between the two gaps isn't connected to the power at all.

I've seen this double-gapping idea suggested before. Quite tricky to do this with LGB type rail I'd have thought? How do you support the tiny isolated piece of rail and keep it from drifting and closing the gap? Some sort of elongated insulated rail joiner perhaps, with the short piece epoxied into the middle?

I wouldn't have thought it mattered as long as the reversable section is long enough for the entire train (this seems to be the general recommendation for reverse loops etc.). The first metal wheel hits the single gap and the polarity is reversed due to the short detection, then no more shorts as the rest of the wheels run over the gap. If the reversing module works via external detection (reed switches or whatever) then no problem as the reversable section is pre-set to match polarity with the incoming track, and you don't switch polarity until the entire train is within the reversable section.
 
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To avoid any issues, I'm planning to take the power for [point decoders] from track inside the main layout - i.e. somewhere before the bottom Wye point and above the top Wye point in the diagram.

My thinking is that this would avoid any issues with the feed to the decoders swapping polarity from +ve to -ve, as might be the case if I located the decoders next to their respective points. Does this sound OK?

It's DCC, the point decoder doesn't care about the track polarity.

Personally though, I'd wire the point decoders to a separate DCC bus rather than directly to the track. That way you can run the track on DC (or turn off track power altogether) and still keep DCC control of the points.
 
As Nick says, it should not matter if the feed to the switch decoder is in or out of the section controlled by the reversing loop module.
 
What are members' DCC experiences with the Massoth reverse loop module? I've been considering them for use myself and would like to know if others are satisfied with the way they operate.
 
I have 2 of them - one for a "Wye" and one for a reversing loop. Both have worked fine for several months.
I liked the fact they came as a complete kit - reversing unit, isolating rails, insulated joiners, diodes and track connector tags. In the end I installed them such that power to each unit comes from outside of the Wye and the reversing loop as this was easier for me.
My only issue has been forgetting that when I run through the arm of the Wye controlled by the reversing unit, I need to make sure that any train with metal-wheeled rolling stock fit's entirely within the controlled track. The times I forgot has triggered a short circuit!
Hope this is useful info.
 
I have a 'dog bone' as one of my layout lines.
As the two 'reverse loops' are a distance from each other and connected by a twisting and winding single track, I have used two of the Massoth modules under 'sensor' mode (one in each loop),
The modules come with all of the 'double gap' track bits and the diodes for the sensor operation.
The module 'sensor' detects the presence of the metal wheel (using occupancy system) and switches the polarity so no 'shorting' happens.
Works very well indeed but do make sure that all connections are tight and greased for protection from corrosion.
My modules sit inside little huts on a raised platform to protect from wet and damp.
 
I have just bought said module Massoth 8157001 and despite repeated attempts I cannot get it to work.
I have it set up as shown in the diagram below.
This is with a single short wheelbase loco which is much shorter than the isolated section.
I have tried it with and without capacitors on the sensors, and with and without short circuit detection, and with and without sensor sections.
In all cases it works at left hand end but not the right, the command station detects a short and stops the loco.
If I reverse the "out" connection it works at the right hand end but not the left.
This suggests to me that the unit is not switching the polarity of the DCC signal, or perhaps it is not switching it fast enough before the command station detects the short. My command station is a Lenz LZV100.
Does anyone have any suggestions or do you think the module is faulty?
Thanks for any info, and if anyone has one of these with Lenz command station perhaps they could PM me?
wiring.jpg
 
A bit late but can I suggest the Lenz LK200 reversing loop module may be a better bet in your circumstances.
 
Yes it sounds like the command station is too sensitive for the very quick short circuit.
BUT... if you were using the 'sensor' wiring, then there should be no 'short' to be detected by the command station.
You may have a defective module.... but there again.....
I had a problem when I first wired up one of my two modules that did not seem to have a reason for existing (the loco would 'pause' when going into the loop and sometimes not move or sometimes carry on. I thought it was the module and tried the other one in its place but the problem persisted.
I had checked the wiring etc quite a few times already but when I found that the second module was displaying the same behaviour I decided to really very closely examine the wiring....
I had transposed two of the 'sensor' cables and one of them was also making intermittent contact due to a pice of grit stopping the screw from fully clamping the cable to the rail.

Once that was sorted...no pauses and perfect running.
 
Yes it sounds like the command station is too sensitive for the very quick short circuit.
BUT... if you were using the 'sensor' wiring, then there should be no 'short' to be detected by the command station.
You may have a defective module.... but there again.....
I had a problem when I first wired up one of my two modules that did not seem to have a reason for existing (the loco would 'pause' when going into the loop and sometimes not move or sometimes carry on. I thought it was the module and tried the other one in its place but the problem persisted.
I had checked the wiring etc quite a few times already but when I found that the second module was displaying the same behaviour I decided to really very closely examine the wiring....
I had transposed two of the 'sensor' cables and one of them was also making intermittent contact due to a pice of grit stopping the screw from fully clamping the cable to the rail.

Once that was sorted...no pauses and perfect running.
Thanks for the feedback Mike. I have checked all the connections with a meter and I have tried swapping just about every combination of cable, but I'll give it another go based on your experience. I've also asked Massoth to comment on my wiring diagram.
 
Your schematic differs from the way I've wired up my Massoth RL modules in one aspect - the Input (IN+ and IN-) leads are attached to the same side as the Output leads (Out+ and Out-).

In my case I wired the module up so that IN and OUT are on opposite sides (this is how I interpreted the diagram in the manual) and the modules have worked just fine. (I use mine in sensor detection mode with supplied diodes fitted, so can't comment on short circuit detection mode.)

Also. I have a Massoth 1200Z central station with mostly default settings (only change is max amps before it trips which I lowered).

Hope this helps.
 
Your schematic differs from the way I've wired up my Massoth RL modules in one aspect - the Input (IN+ and IN-) leads are attached to the same side as the Output leads (Out+ and Out-).

In my case I wired the module up so that IN and OUT are on opposite sides (this is how I interpreted the diagram in the manual) and the modules have worked just fine. (I use mine in sensor detection mode with supplied diodes fitted, so can't comment on short circuit detection mode.)

Also. I have a Massoth 1200Z central station with mostly default settings (only change is max amps before it trips which I lowered).

Hope this helps.
Thanks Phil. I have tried swapping in and out polarity but still doesn't work both ways. I think it might be one of the sensor circuits as if I swap sensors the other direction works. Unless Massoth tell me otherwise I think it is either broken or alternatively it doesn't work with Lenz CS and I will end up going with Alan's suggestion of buying a Lenz LK200 (which @ £55 is cheaper than Massoth).
 
I got a Lenz LK200 this morning, it took 5 minutes to wire up and worked first time. Much simpler to set up and as far as I can see no mechanical relays inside.

Thanks to Alan (stockers) for the suggestion. I never consider Lenz for this as I thought they wouldn't be able to handle the current, but this device is rated at 5A which is more than enough for my layout.

Also full marks to DCC Train Automation http://www.dcctrainautomation.co.uk for extremely quick service. I ordered it online about 3pm yesterday and it arrived this morning.

I will let you know when I hear back from Massoth.

Picture of connections - simples
2017-05-06 11.47.10.jpg
Picture of box
2017-05-06 11.47.21.jpg
Innards of box
2017-05-06 11.58.30.jpg
 
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