Reverse "loop" query - all help appreciated!

[srt11]

Hi All,

 

Another question on this perennial problem...

 

System: OO gauge; DDC - Gaugemaster Prodigy Advanced2, fed through a DCC concepts Alpha Box.

 

The attached image is a simplification. Essentially, the layout is a single loop doubled up on itself, creating a helix from the lower level to the upper level (I hope that makes sense!). The blue arrows show the direction of travel (top arrow, pointing to the right as you're looking at it, is the up line (to London, for those who care...). Because the track is in essence a single track, I (stupidly, it turns out) wired it so that on the Up line has +ve on the top rail and -ve on the bottom rail  [yes, yes, it's DCC, but you know what I mean!], whilst for the Down line, the +ve is on the bottom rail and the -ve is on the top rail.

 

In terms of the attached diagram, the bottom loop (marked 2)  is the lower level including the helix-ed track. The upper level is the top half. As per the Anyrail system's reverse loop identification, there are potentially two positions where a train can reverse (in this diagram, only the second reverse loop is highlighted, but it should be clear enough). First is at the crossing on the right (marked with a green arrow), creating a balloon loop (marked 1). Second is if the train goes off the main through the double slip (marked with a red arrow), through the sidings (there are many, which I've left out of the diagram), and then up through the diamond (marked with a yellow arrow) on the left.

 

My feeling is simply that if I put a Reverse Loop Module (RLM) at the midpoint of the balloon loop (marked with a green cross), and then rewire so that +ve and -ve flip over at the RLM point in the balloon loop. I think this will solve most of the issues, but I am unsure whether I need another RLM at the left hand end of the station (after the points) (marked with a purple cross - I'm not sure whether I would need it on the up or down line). This, I think, would be the simplest option (there is no need to do anything then with the lower level), because instead of treating the problem as one of a reverse loop, it is really a problem simply of mismatched "polarity". (FWIW the loop marked 2 is approximately 8m of track in total so more than enough for two whole trains either side of the RLM, assuming it is placed at the apex of the curve)

 

The reason for this is that (a) I'm not actually aiming to create a reverse loop, but it's merely a consequence of the overall trackplan being a folded loop, with crossovers, and (b) I obviously actually do want the capacity to use the crossovers and slips and whatnot in a (pseudo)realistic way, without shorting.

 

Finally, for what it's worth, the top level is a (simplified, obviously: I don't own a 50m long shed...!) version of Neath General (in a non-Beeching world).

 

Thanks!

 

Sean.

[Michael Hodgson]

I would reverse the polarity of one ot the tracks in the station area (whichever one is easier to do) so that the station crossovers do not cause a polarity clash and the  whole of the station is of just the one polarisation.

 

I would then treat both 1 and 2 as reversing loops each with their own module.

Section breaks immediately to the right of the right hand crossover for loop 1 and at your purple crosses for loop 2.

 

[5BarVT]

Not quite sure how much you are intending to rewire, if any, and that affects what is best to do.

IF you are leaving the polarities as they are, then the place to put the RLM is feeding all the track between the yellow diamond and the point to the left of three green arrow and any other sidings connected.  You then have to make sure that only one train crosses the boundaries at any one time: i.e. you couldn’t run through the diamond towards the red slip at the same time as running from the green cross towards the yellow diamond.  The retiring involved in that is just separating all those tracks from the remainder of the layout.

Alternatively, if you use two RLM one for the ‘green’ loop and one for the ‘purple’ loop you would need to alter the polarity throughout yellow diamond to green point area.  The purple RLM would be better with a shorter length (doesn’t have to be the ballon bit) so that you reduce the risk of two trains fighting over polarity.

The RLM section must be longer than your longest train with connected wheelsets (e.g loco at front and coach with pickups at rear) or it will fight with itself over polarity!

Paul.

[srt11]

Thanks both.

 

First, I've just noticed that in the diagram the bottom set of blue directional arrows are wrong! [It must be a subconscious attempt at the BR double arrow.....!] Obviously they need to be the other way around. But that doesn't change the substantive problem.

 

Second, I think Michael Hodgson's suggestion is the one I will go with ie just isolate the whole station area and then just put RLMs in either side. The rewiring is not a problem really as most of the track has droppers but theyve not yet been permanently attached (so straights will just be flipped over). Also, given my usual hasty approach to such things I'm used to having to recolour-code wires as it were (I use quite a bit of red and black insulation tape ...), so that's not too problematic either.

 

Unfortunately given time etc it may be a while before I get round to doing this (as the trains happily go round and round, even over my hilariously bad removable sections and terrible track work, improvements naturally take second place over running the trains) but I will try to see how it works ASAP.

 

[I really do wish I was even vaguely competent at drawing. I've got this great image in my mind but I'm so "dysgraphic", if that's a word, I can't even draw a straight line with a ruler.]

[RobinofLoxley]

Have you had trains operating on this layout?

[Michael Hodgson]

1 hour ago, RobinofLoxley said:

Have you had trains operating on this layout?

Yes, a good idea to test as you go, as it makes wiring errors easier to find.  If there's a short circuit somewhere it will be in the bit you've just done,

[srt11]

3 hours ago, Michael Hodgson said:

Yes, a good idea to test as you go, as it makes wiring errors easier to find.  If there's a short circuit somewhere it will be in the bit you've just done,

Trains go around perfectly well. There's no short circuits, other than those caused by the noted reverse loops. Hopefully I'll get a little video of it soon.

[RobinofLoxley]

Pardon me for asking @srt11 but as it sounded quite a complex layout I could foresee trouble. There have been posters asking for help having laid a lot of track without any testing. 

 

Still from what you have said the first thing I would do is correct this error with the polarity connections. Even if you find a work around imagine what could happen if you wanted to install a booster for example. 

[srt11]

HI @RobinofLoxley. I will admit the plan give the impression of complexity, but that's just it. The plan is actually very simple: a single oval, looped over itself (imagine a slinky - one of those things that's just a simply bit of wire curved to create a cylinder, that can go down stairs - that is in essence what I have done). And it does work perfectly fine all around (electrically speaking: the less said about my track laying the better...). The sole issue is simply that by a function of the geometry that there will be polarity issues at crossovers (of which, there are only two, on the upper level at the station as noted), and I think the solution is as simple. But simple solutions to simple problems are often the most difficult things to get right....

 

By some wonder, I have an hour or two free today: I will need to tidy up the track (I am not a tidy worker), so that it's visible as such, and I will get some photos up, and I'll try and get a (small due to upload limit) vid of trains going round.

[Harlequin]

1 hour ago, srt11 said:

By some wonder, I have an hour or two free today: I will need to tidy up the track (I am not a tidy worker), so that it's visible as such, and I will get some photos up, and I'll try and get a (small due to upload limit) vid of trains going round.

To save you some time and annoyance, note that RMWeb doesn't host videos itself. The recommended way of posting video content is by uploading to YouTube and then embedding a link to that.

 

Looking forward to seeing your folded layout.

 

[srt11]

Hi @Harlequin.  Thanks - I had noted that. I may have to actually do a youtube it seems (I've no idea how; should be fun). 

 

I tried to do some filming today but it's really hard running around a train holding a phone, whilst realising (more than once...) that there are obstructions on the line (as I said, I'm not a tidy worker), and the track had come apart at one point....

 

Nevertheless, here are some photos - the Western is blurry because it is moving!

 

The "overhead" shot (which involved me nearly burning my hair on the light) shows on the left (as you look at it) part of loop 1 from the diagram, along with the Up and Down lines (UP is the line on the furthest left, and furthest right). The curve on the top right is the entrance to the station (which if you know Neath, is prototypical - eventually if I have the time and develop the skill, that entire section will be done up as if going over the river).

 

The photo with the cl37 is coming into the station. You'll notice, on the rhs of the autocoach, the lines going down into the helix effect.

 

I can put up more photos, but I will set up another thread elsewhere and link thereto.

[5BarVT]

Hi Sean,

Thanks for the photos: guess what, they generate more questions!  I now understand your helix and reversing loops.  Looks like about 1 1/2 times round the room.

First question is the diamond crossing: I see some of what I think are code 75 labels - is your crossing SL-194 dead frog or SL-E194 electrofrog?  It might make a difference to the solution.

Second is the extra sidings (and a quick look I’ve had at Neath General East and West box layouts.  Inside the top ‘reverse loop’ there are some sidings - do they connect to both sides of the loop so as you can run in from the Up Line but run out onto the Down Line once you have an engine on the other end?  If so, that changes the options on RLMs.  Likewise at the bottom of the helix, there seem to be sidings off one side of (what I think is) the reverse loop going round to the other side of the room - I’d like to know more about how they connect to see if that impacts on RLMs.  And finally (for now?!!!), in the station, how does the middle siding connect at the end we can’t see (the real thing connects to the Up Line)?

Paul.

[DCB]

On 03/02/2023 at 19:34, srt11 said:

Hi All,

 

Another question on this perennial problem...

The two Reverse modules sound very sensible,  It sounds like, and I hope I'm wrong, that up and down lines are wired to the same bus.  That is a pretty bad idea.  Ideally a layout that size should have several sections or power areas which can be isolated for fault finding.  I reckon 6 yards of track and a dozen points as the maximum chunk for one feed.  That way you can flip every thing off and reset the switches one by one until the fault is discovered or the gremlins get bored and wander off to annoy someone else  From the photos you will need boosters and I would suggest 1 amp polyfuses to protect the droppers, so a re wire is probably easiest to do now before the scenery.  Bus wires beside the tracks are easier to move than under baseboard if tracks need realignment and are easily hidden by ballast.    Keeping lights, points, any other accessories on different circuits to traction is also a big help for fault finding.

Your track layout looks a bit odd with the diamond marked orange.  Is that prototypical?   The junction is almost always beyond the platforms not before it,  platforms are usually paired up and up   plus down and down.

Its probably not worth bothering with live frog diamonds on DCC with modern post 2000 locos.   They made a massive difference with Hornby Dublo Castles and the like with at most 2 wheels picking up per side but times have moved on,

Don't forget to run trains.  You can spend 20 years working on a layout and suddenly realise you have never had a single proper operating session,    You could always say "Stuff the electrics" and go Radio Control.

[5BarVT]

3 hours ago, DCB said:

Your track layout looks a bit odd with the diamond marked orange.  Is that prototypical?   The junction is almost always beyond the platforms not before it,  platforms are usually paired up and up   plus down and down.

Yes, prototypical, straight out of the Neath General West playbook upon which the layout is based.

Pairing of platforms: depends whether you are talking about 2 track or 4 track areas and goods lines or passenger lines.  Most GWR 4 track areas were Up/Down/Up/Down (Paddington to Didcot, Lapworth to Moor St, Filton Bank, Severn Tunnel to Cardiff) though others were Up/Up/Down/Down (Banbury, Cogload to Norton Fitzwarren, Challow to Wantage Rd).  Agreed that multi platform stations on 2 track lines are more likely to be Up/Up and Down/Down but Goods avoiding lines at such stations are often a separate pair e.g Taunton, Exeter, Wolverhampton LL, Reading.

Paul.

 

[srt11]

Hi @DCB,

 

Some useful points (for want of a better word...) there - thanks.

 

I'll note that at the moment, track power is run through a booster for all levels. When I get to the point where I'm happy with it running around the main (almost there; it's basically the reverse loop issue), then I will add in another booster (so it will be booster 1 for top level, booster 2 for bottom level and helix, booster 3 for accessory bus, which is more than sufficient).

 

As for faults: the gremlins appear to be solely concerned with my carpentry, track laying, and whenever I open a pot of glue - for some reason my electrics are gremlin-free (famous last words...).

 

Live frogs - I get what you mean, and for most of my locos there's no real need for them. However, I do have a few lovely little locos (Pecketts, the Rocket, etc), which do get trapped by the smallest dead frog (adding stay alives will probably eventually happen, but I feel that is a secondary response to the underlying problem ie better to have a live frog (easily done with Cobalt IP digital points, which is what I use).

 

Forgive my ignorance, but would you be able to explain '1 amp polyfuses to protect the droppers' - I'm really not sure what this means!

 

And yes - I do run trains, probably more than I should relative to actually doing/improving things -- that's why things have taken me so long to get even to this stage!

 

As for prototype, @5BarVT has got there before me. Neath only ever had two platforms, with the Up line to London being platform 2 (never understood that as a child, and still don't know). The thing to realise about Neath is that it is old, very old - it goes back to at least the mid1860s and has never been altered (other than rebuilding the station, and the post-Beeching rationalisation, the location and geography has remained the same since it was first there. [So, eg, the siding in the middle of tracks at the station is actually a consequence of the track having been originally Brunel's broad gauge: when they moved to standard gauge there was sufficient space to shove in a siding, so they did.] Important to note that the Down platform is only a platform for the main line (ie the lines on the other side were the sidings (in particular, there were two lines squeezed between platform and goods shed (with the third line being a run through the goods shed). I've drawn my version of Neath-as-it-might-have-been from the RA Cook (?) trackplans, along with the (rather quite limited) photos of the station area.

 

Thanks all for the help so far - I will try and update this thread re the reverse loop issue when I get that done, but for now I think I will shift the general exposition/photos etc to the the Layout Topics forum, under the title "Rimmer Junction (Neath, as it might have been....)".

[5BarVT]

1 hour ago, srt11 said:

And yes - I do run trains, probably more than I should relative to actually doing/improving things -- that's why things have taken me so long to get even to this stage!

Isn’t that what it’s all about?  Mind you I’m a scenery light, operation heavy, person so I’m rather biased!

Paul.

[Michael Hodgson]

3 hours ago, srt11 said:

Neath only ever had two platforms, with the Up line to London being platform 2 (never understood that as a child, and still don't know).

 

When the railways were first built, many of them considered London to be their most important station and even had names like the London & Somewhere Railway, and there weren't very many passenger trains a day.  So the way timetables were advertised was a column of station names down the middle of the page, with departures from London in columns to the left and trains back in columns to the right.  So you read down the page for the times of trains from London. and up the page for trains back.

 

The Welsh valleys were an exception to this practice, and their up & down directions were literal bacsed on the geography.

 

Platform numbering is another oddity.  Often the platform with the main building was platform 1 but there wasn't any real consistency, and numbering isn't always the same following layout changes.  Here at Hitchin they swapped the numbers of our two platforms a few years ago; I think the reason was to standardise numbering along the route to make it easier when station announcers who covered the whole suburban route from Kings Cross.  And Kings Cross itself of course has a Platform Zero as well 9 3/4!