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Britmod-OO Challenge entry - Return to Sender


cromptonnut

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For planning purposes:  module and operator are located in Horley, Surrey.

 

I've only just started work on this, much of it is still "bits of wood needing screwing together" so I hope it qualifies as a new build.

 

My module is big, and has an overall footprint of around 11ft x 7ft.  It is designed to be a 'return loop', to reduce handling of trains once they get to the "end of the world".

 

The module consists of ten boards, two for the "junction" and 8 forming a circle, the tops of which were laser-cut for me by Tim Horn.

 

The module is twin track on the entrance side, with a junction splitting into two single track branches which can both be approached in either direction.  The trains then enter the loop and come back, crossing over to the appropriate line for return if required.

 

There are four three key features worth mentioning.

 

1) The use of Minx Microdrive point motors (I have previously used these on my O gauge project but not with OO so it's experimental for me).

2) Short tunnels to provide a "scenic break" with backscene so the lines going opposite ways at the junction can't be seen from each other.

3) A small single track station, so that short local trains can stop and long expresses simply pass through.

 

Oh, and the biggest challenge?  I drive a Fiesta...

 

So.  Still with me?  Here's the track plan.

 

post-8328-0-87503100-1426617347_thumb.jpg

 

Updates will be posted as the boards and legs get built.

 

The name of the layout is a tribute to my late father-in-law who spent years working for the post office, on the basis that trains sent onto the module are soon returned back to the layout in the other direction.  There will most likely be a post box and several other relevant cameos somewhere on the circle.

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It has some potential for that - but until I get further on in the track I can't tell if it will actually work in that way.  Watch this space...

 

However I don't have room easily at home to put the whole thing up indoors and 36" radius is much larger than I need, as just about all of my stock is "off the shelf" a circle of radius 2 on the kitchen table is adequate should I need running in abilities, and in that case I should probably just get on and buy a rolling road.

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I guess a little background could be useful.

 

When "modular" was first being bandied around I studied a lot of Youtube videos to see how things were being done using other standards around the world.  Many of the US arrangements had huge round modules at the end which provided an opportunity to turn trains without handling, often having 5 or 6 "staging roads" so multiple trains could be held there. 

 

My budget, and space available, didn't allow me to build a mega module like that but there was an opportunity to fit in a single line circle, with a junction to fit a double track input, so Tim Horn was commissioned to make some 1/8 of a circle boards to my design (tops only - the thought of cutting 16 x 22.5 degree board ends and 6ft/7ft radius circles accurately would never have worked but to a laser cutter it's a doddle.  As the other parts required were just rectangles I simply went to B&Q with a cutting list rather than wasting Tim's time.

 

In hindsight I should probably have made the boards larger to allow a passing loop at the station, or even a double track loop all round, but that then may not have made it possible to put the thing together inside at home which would have made the exercise rather futile on my part to spend all that money on something that may only be used 2 or 3 times a year.

 

Interestingly I got a 'freebie' 9th top from Tim as it fitted out of one board so that can be used to replace the board where the 2 lines join to the left of "straight on", allowing me to operate in a roundy-roundy configuration as SHMD suggested a couple of posts back - but that is something that will come later as my priority has to be getting the basic arrangement ready hopefully for our SECAG test modular meeting which may be at the end of June, purely to test that random strangers can follow instructions and our boards can fit together and work properly in some sort of functional layout.

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Quick update... whilst board construction continues, I had a go at "snow" on an offcut of wood.

 

Just as much of a failure as last time, so I'm not going to bother.  Yellow snow I can live with (in small doses) but blue snow?  Naaah.

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Now you have added a 2-rail return loop, you will probably have to add a DCC decision to the "standards" as to whether you want to run the double track you just included as "East-West", or all one direction or the other. I suspect you are going to need some "auto reversers" in your system for that and for those having crossovers in any other double track modules. I'm sure the existing modular groups can offer some excellent advice on the technicalities.

 

Andy

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Already incorporated an auto-reversing module into the plan, spent half an hour working out where and when left and right become inner and outer, and at what point left meets right so I know where to put the insulating breaks.

 

In many respects, normal DCC operating rules (ie the need to auto-reverse on a loop) are covered outside of the rules as they are a 'given' when incorporating these sort of modules - which will of course be fairly rare I expect anyway.

 

Here's my scribblings so I know what to wire, using 4 pole Molex connectors (PC power exenders) across the 4 boards affected; beyond the isolating fishplates left and right simply become inner and outer.

 

post-8328-0-88876700-1427144738_thumb.jpg

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Already incorporated an auto-reversing module into the plan, spent half an hour working out where and when left and right become inner and outer, and at what point left meets right so I know where to put the insulating breaks.

 

In many respects, normal DCC operating rules (ie the need to auto-reverse on a loop) are covered outside of the rules as they are a 'given' when incorporating these sort of modules - which will of course be fairly rare I expect anyway.

 

Here's my scribblings so I know what to wire, using 4 pole Molex connectors (PC power exenders) across the 4 boards affected; beyond the isolating fishplates left and right simply become inner and outer.

 

attachicon.gif20150323_210452.jpg

 

I was thinking of the requirements for auto-reversers (or not) on the other peoples modules.

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Unless I've missed something blindingly obvious, it shouldn't make a difference - a standard twin track feed comes into the module via two banana sockets as per the standard.

 

The junction section is treated as one section of the module and wired up in the normal way with frog polarity changed where necessary by the point motors.

 

Then after all the pointwork there are isolating fishplates on both rails, which is treated as the reverse loop and wired as appropriate through the Lenz auto reverser which I have.

 

The very basic plan in post #1 is "the module" in its entirety that I am constructing, so as far as modular goes all that is critical are getting the feeds the right way round, then hopefully on the assumption that I have wired everything up properly (!!!) as I build it, the point motors and auto reverse module should deal with all the fancy electrickery.

 

The only complexity would be if the main power feed to the layout from the DCC box was somewhere within the loop and the auto-reverse module then powering the rest of the layout, which is partly why I chose to interconnect my module's boards with a different connector to prevent it happening.

 

I hope that makes sense - it does in my head at least!

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Unless I've missed something blindingly obvious, it shouldn't make a difference - a standard twin track feed comes into the module via two banana sockets as per the standard.

 

The junction section is treated as one section of the module and wired up in the normal way with frog polarity changed where necessary by the point motors.

 

Then after all the pointwork there are isolating fishplates on both rails, which is treated as the reverse loop and wired as appropriate through the Lenz auto reverser which I have.

 

The very basic plan in post #1 is "the module" in its entirety that I am constructing, so as far as modular goes all that is critical are getting the feeds the right way round, then hopefully on the assumption that I have wired everything up properly (!!!) as I build it, the point motors and auto reverse module should deal with all the fancy electrickery.

 

The only complexity would be if the main power feed to the layout from the DCC box was somewhere within the loop and the auto-reverse module then powering the rest of the layout, which is partly why I chose to interconnect my module's boards with a different connector to prevent it happening.

 

I hope that makes sense - it does in my head at least!

 

If you have double track, are there two banana sockets or four?

 

Andy

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  • 2 weeks later...

Two. It's DCC

 

It's all still 2-rail.

 

A double track set up with two of those reverse loops - one at each end - would have no auto reverser capacity or timing issues if the East and West routes on each module had the option of their own isolated set of plugs. A shorting cable to join them if needed would only cost peanuts.

 

I have no idea how the current modular groups handle double tracking with reverse loops somewhere, but I would imagine that once you have auto-reversers dynamically operating on one module, you may then need them on others too.

 

Just trying to think ahead.

 

Andy

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I was working on the basis that as this is going to be "the end of the line" in whatever configuration it happens to be used in, the two tracks in are fed in the normal manner, the junction is wired in the normal manner with frog polarity changing as required, then the loop itself is fed from a reversing module, which changes polarity appropriately as a train enters or leaves the loop on the loop only, leaving the rest of the setup unaffected.

 

The key of course is making sure that the loop section is longer than your longest train - and it's about 18ft if my maths is right, so that should be more than enough.

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I was working on the basis that as this is going to be "the end of the line" in whatever configuration it happens to be used in, the two tracks in are fed in the normal manner, the junction is wired in the normal manner with frog polarity changing as required, then the loop itself is fed from a reversing module, which changes polarity appropriately as a train enters or leaves the loop on the loop only, leaving the rest of the setup unaffected.

 

The key of course is making sure that the loop section is longer than your longest train - and it's about 18ft if my maths is right, so that should be more than enough.

 

And no-one tries to send a second train onto it as the first is leaving via double track. Which is highly likely with multiple operators and 18 ft of room.

 

Andy

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I was thinking of the requirements for auto-reversers (or not) on the other peoples modules.

I can see the potential of problems (and a possible spec requirement) if more than one module has an auto-reverser.

 

I believe that in the early days this is going to be highly unlikely. The issue right now is getting sufficient number of modules together to make a single track gathering possible, let alone double track.

 

As for single track, or even single into double/multiple junctions, it just isn't going to make any difference - the whole point of DCC being that the locos are driven not the track.

 

One area that does concern me though is the potential local-mail DCC configuration. As I currently understand it: the whole track is on a single 2 wire bus. So what happens when the yard-master on module X plugs in his DCC controller to manage some local shunting? Is that "local" yard isolated and the local controller powers the local yard, or are we just assuming that the DCC controller plugged in to the main bus locally is fully compatible? (or potentially dialling up the wrong loco in some other yard)?

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And no-one tries to send a second train onto it as the first is leaving via double track. Which is highly likely with multiple operators and 18 ft of room.

 

Andy

 

On a double-track return, yes.  My module is a single track reverse loop.  All the point polarity switching is done outside of the reverse loop by other independent means.

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One area that does concern me though is the potential local-mail DCC configuration. As I currently understand it: the whole track is on a single 2 wire bus. So what happens when the yard-master on module X plugs in his DCC controller to manage some local shunting? Is that "local" yard isolated and the local controller powers the local yard, or are we just assuming that the DCC controller plugged in to the main bus locally is fully compatible? (or potentially dialling up the wrong loco in some other yard)?

 

I believe that there is one main bus for the whole layout.  The potential for 'taking control of the wrong loco' exists in every modular system unless it's "one train in steam" principle which rather defeats the object of the multi operator modular system!

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On a double-track return, yes.  My module is a single track reverse loop.  All the point polarity switching is done outside of the reverse loop by other independent means.

 

Not according to your diagram in post #1. That's why I was concerned. If you are using the double track, then the entering train wheels short to the main line inbound to the loop and the leaving train wheels short to the same polarity main line outbound.  There's a lot of opportunity for both shorts to occur simultaneously and confuse the reverser.

 

If you are using single track, then I agree with your reasoning. Obviously you cannot physically have two trains entering and leaving on the same single track. So the reverser will handle that OK.

 

Andy

 

Andy

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The "isolating section" is on the single loop - nowhere near the points :)  I probably haven't explained it that well but it does work in my head...

 

I'm surmising a 2-rail problem, not a points issue.  But. . . . .

 

Actually, I was forgetting that most UK stock has plastic centred wheels. If your isolation gaps are wide enough and filled level with insulation, then the metal rims won't short across the section gaps as they pass over. But locos, lit coaches, etc.,  with pick-ups on multiple wheels will short the gaps regardless.

 

Andy

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I believe that there is one main bus for the whole layout.  The potential for 'taking control of the wrong loco' exists in every modular system unless it's "one train in steam" principle which rather defeats the object of the multi operator modular system!

Then with no local control isolation there is a real possibility of my DCC controller being incompatible with the main system. Although (as I understand it) All DCC signals are in theory the same, the hand-held units are not all compatible. So for example someone turning up with a NCE cab for their local yard will be incompatible with the Dynamis Lenz system being used for the main? It also means that the power output of the main and boosters needs to be adequate for all the yards.

Not to mention the reconfiguration of all those slow yard shunters that were never intended to venture on the main. (I have one that at max speed will take minutes to cover Kenton's Curve so is going to hold everything up!)

 

I was under the (seemingly mistaken) assumption that local would truly remain local.

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Unless I am misunderstanding things, in most "modular meets", a 'control system' is specified at the beginning of the planning, and those with compatible controllers bring them along.  I'm also hoping to have a WiThrottle setup via JMRI so anyone with a compatible phone, tablet or laptop that can run a suitable enginedriver app can "join in the fun".

 

In the future, we will probably need some power boosters - but I think for the first few meets we should survive.  Of course, when someone else organises a meeting, they may decide to use a standard that isn't compatible with the Lenz stuff I have, so I may have to either hope that they have a wifi control option, or I just watch the trains go by, or don't come.

 

If you have a large module, then I guess there's no reason why you can't have an isolating gap on both rails, with your own controller for the yard, with some kind of safety interlocking to prevent running from main to yard, or vice versa, and a switch to flip between the two systems so that you can bring your NCE system along to operate (for example) your large loco depot, and then have a 'feed section' that can be switched from the main controller to your controller, and perhaps some banana plug jumpers so it can all be operated from the main bus if it all happens to be compatible with your system.

 

Definitely something to think about in the early planning stages - I'd certainly be interested to find out how other standards get round this issue.

 

Free-mo simply states

 

S5.1 LocoNet compliant DCC and accessories are standard for interoperability within and between Free-mo groups. For more information about LocoNet Technical specifications consult the Digitrax website.

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I'm also hoping to have a WiThrottle setup via JMRI so anyone with a compatible phone, tablet or laptop that can run a suitable enginedriver app can "join in the fun".

 

Though I don't have a "compatible device"/permited to load the App - this is something I really would like to see in operation in June (especially as an old one apparently can be picked up ca £25.

 

As for the

S5.1 LocoNet compliant DCC and accessories are standard for interoperability within and between Free-mo groups. For more information about LocoNet Technical specifications consult the Digitrax website.

My feelings on Free-mo (or should that be now named DigitraxMo?) standards. Forcing everyone to purchase and use Digitrax at the expense of a better popular system! Excluding them, use Digitrax or forget joining in.
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As there are so many different controller options, you'll probably never really find one "best for everyone" system and it's really down to the meet organiser to provide or organise enough items - I have two Lenz controllers, you can use the laptop for at least one further throttle, and then the withrottle/engine driver wireless options does give some choices.  If at another meet someone chooses another system then if they have the wireless option I can join in using my phone or old laptop, or just be happy to wait my turn for someone else's controller. 

 

One of the downsides of DCC, of course, is that there are a variety of controllers out there whereas if "bog standard" 2 rail DC was chosen then you'd just have local control on each board and "pass over" to the next - which could create more problems than trying to settle on a DCC system!

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