Hornby DCC Power And Accessories

[Fishmanoz]

Excellent analysis and solution Chris, I’m almost certain you’ve done it.

 

I’ve been reading through this thread sequentially so was trying to get my head around your first design before I came to the second.  Let me emphasize for a start the general rule of isolated sections in reversing loop layouts - you cannot have more than one train entering or leaving any isolated section at any one time.  You did point this out as part of your first design but you didn’t fully follow it through.  For me, the consequence of this design limitation for this layout is that, if you want to run more than one train at a time with freedom of where the trains go, the inner and outer loops must be isolated from each other, and each end must be isolated from the other on each loop.  That will mean 4 isolated sections will be needed run by 4 RLMs.  Then there is an issue in that there is another place at which the isolated sections could interact and that is at the Y point to the TT and I’m pretty sure you would end up with RLM1 and RLM2 working against each other when a loco enters the TT from the upper leg of the Y point, but let’s not worry about this given the 2nd design.

 

So let’s now look at design 2 and does it meet the practical limitations I gave above (inner and outer loops isolated, each end of each loop isolated)?  The answer is yes it does, it has the 4 isolated sections needed.  In addition, the blue/brown analysis of all the inner workings just proves that for phase management (what RLMs do), it is no more than 2 Y sections, one on the inner loop and one on the outer, and they are fully isolated by the districts in the design.

 

Just one final issue for ease of analysis of designs similar to this - I think it is conceptually easier to think of this layout as needing power districts and boosters rather then isolated sections and RLMs.  And that tells us something else too - as far as phase management is concerned, RLMs and boosters are exactly the same.  The difference between them only relates to the booster increasing the power available to the layout, something the RLM doesn’t do.

[Fishmanoz]

Dan, you posted while I was writing mine.  Chris has already suggested you need to run a DCC power bus for this layout (in fact 4 independent buses) given the complexity of the number of points power passes through and the likelihood that DCC point clips won’t be able to cope.  As an absolute minimum you have power connections at each end of each RLM.  One end of each RLM is then also connected back to your single DCC controller and the other end goes to each of the 4 isolated sections or power districts.  Does that make sense?  If not, Chris will be along soon I’m sure with the more complete (read long) answer.

[Bigmandanc]

Ah ok, I see now. One controller with 4 power connectors. That makes sense. So as long as the lead of the loco passes on to the next section before the dummy comes in, they shouldn't short circuit anything. I'm beginning to think I might build this layout them have someone from one of my local train groups come out and explain it all to me in person, the connecting up the points etc, so everything is powered properly. Chris has been a godsend, I was so lost before, but it's all starting to click now! Thanks for simplifying it for me fish!

Kind regards

Dan

[Fishmanoz]

Yes, you could build it without knowing just how to wire it, as long as you include all the IRJs in the right places.  Miss just one of them and you are in trouble.  Then you have 2 choices:

 

1.  You could try it using 4 DCC power connectors, then more of these at the ends of the RLMs, plus DCC point clips on every point, or, far better

 

2.  Run 4 independent power buses around under the layout, one for each RLM, with heavy bus wiring for each and dropper wires soldered to the rails and down to the buses, and no point clips.  Droppers would be at every few track pieces and all points.

 

I’m sure Chris will give you links to previous posts on such bus designs.  The wiring will be quite complex and you will have to ensure that there is no interconnection between the 4 buses formed for each of the RLMs at the end remote from the RLM connections to your controller.

[Bigmandanc]

It's option 2 for me. I'm going to be controlling it from my laptop, and I have up to 2 feet of room under my layout, I won't be doing any scenery etc til it's 100 % done, so I have plenty of time to figure out how that works.  I had already thought of dropping wires from under the tracks, and solder them on, that I can do lol. Will definitely need help getting the wiring to click in my head, but once it's clicked, I'll be fine.  Glad I came here for this!

[Chrissaf]

I would try and keep with the metal wheels if you can, they collect less dirt and grime compared to metal ones, and the dirt and grime deposited on the rails causes problems for low level DCC digital signals. You need to clean DCC track and wheels far more often than you would on a DC layout.

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With regard to power track placement, in principle it really doesn't matter as the whole track is live in DCC (even if parts of the layout are powered via the RLMs). Assuming that you are sitting on the side of the layout where the RLMs are shown, then anywhere to the left of the platform on either of the two loop tracks will do.

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But a word of caution. In Hornby world (not so in Peco world), ALL the points would normally be fitted with R8232 DCC point clips to make the whole track and all the sidings live. You have got an awful lot of points in your design and the DCC power has to pass through many clips to reach all parts of the layout. The DCC clips just rely on spring pressure for conductivity, they can work loose, they can tarnish and / or corrode. Over time you might start to experience areas of intermittent power transfer. When this happens the electrical resistance in the clip connections can cause the clips to heat up. We have had reports on the forum of DCC point clips glowing red hot and melting the plastic sleepers of the point, but that is rare.

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With complicated layouts like the one you are proposing and with so many points, I think it would be really prudent to implement a DCC power Bus under the baseboard to distribute the power into multiple areas, so that less reliance is needed on the point clips. I would still keep the clips as well, the reason being, that without the clip the electrical power transfer on the point between the fixed and moving rails would be totally reliant upon the contact pressure of CLEAN rails. The clips, electrically bond the fixed and moving rails together, meaning less reliance is required for the rails staying clean.

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How far you go with a DCC Power Bus is your choice.

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For info: On my own layout (Peco by the way....so no DCC point clips are fitted). I have a power connection on every single track piece and individual point. Albeit I use 3ft lengths of flexi-track so that reduces the number of individual connections and I use 'Electrofrog' switched frog power points. I have in some forum members eyes gone completely over-board, but that was my choice. I do not have to rely on a single track joiner for the transfer of DCC power. The track joiners are just relegated to the task of physically aligning and connecting the individual track rails.

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I, as do many others on here, recommend doing away with Hornby power tracks and Hornby power clips. Instead soldering the DCC controller wires directly to the track rails. Either on the underside of the rail, if connecting the wires as you lay track, or on the outside edge of the rail if connecting after the track is laid. This concept of soldering wires directly to the rails can be extended to a Bus power distribution system. This was the main reason I included my Brown / Blue diagram in my previous reply. I felt that would help explain why it was important to ensure that a Bus implementation was consistently wired for correct rail polarity (DCC phase) right across the whole layout.

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The wires soldered to the rails are called droppers and can be relatively thin wires (I use, as do others, 7/0.2mm wire [this is 7 strands of 0.2mm diameter wire in a common insulated sheath]). The droppers are usually short about 300mm long at most. They in turn, connect to thicker wire [the DCC Bus] that follows an efficient route under the baseboard to cover locations where track is laid. The Bus wires are typically 24/0.2mm or 32/0.2mm wires. It is best to colour code the wires so that you don't get them crossed over and also so that you can distinguish them from other wired circuits such as point operating, signals and layout lighting circuits for example.

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Droppers can be fitted to track pieces at strategic locations on your layout, that in turn connect to the Bus that runs under the board, the Bus in turn connects to your DCC controller. Remember not to connect the Bus to the RLM protected loop ends. This way, your DCC signal is best placed to have the least resistance in its path to all parts of the layouts. How many droppers you install is your choice. I would suggest one on each individual siding, plus the two top loops and the two bottom loops to the left of the Station platform ends (to the left of the IRJs of course). The placement of droppers on the TT and general TT power connectivity is documented in the TT DCC modification link I provided earlier.

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Connecting the droppers to the Bus wires can be done in many ways. The insulation of the thicker Bus wire can be cut back (sliced off with a scalpel knife) to allow the dropper to be soldered to it. You could use solder tag strips to perform a similar function. Or you could use electrical 3 amp screw down terminal strips to make the wire joins. or you could use ScotchLok clamp on Insulation Displacement Connectors (not particularly favoured by many on here, but I don't have any issues using them, which I have done for the last 3 years).

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PS - I cannot stress enough how flat Hornby points need to be laid to be reliable. Many on here reporting loss of power and derailment on points issues have been advised by members to put an additional track pin in the centre of the point (pilot hole needs to be drilled first) to flatten it down close to the baseboard, with the original poster reporting back that their issues have either been resolved or improved. Your layout, with so many Hornby points so close together, may potentially suffer from a combination of these issues.

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PPS - If you haven't bought the track yet. Then I would certainly consider Peco. It does seem to have less issues than Hornby track. Can't really say more than that, as this is a Hornby forum. 😉

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Want to know a bit more about Peco track....check out this link to one of my earlier posts:

https://www.hornby.com/uk-en/forum/another-b2b-question/?p=1/#post-202055

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So in conclusion, I think I have given you enough to think about for the time being. Good luck with it.

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EDIT: I should have put in a holding post and edited it to maintain an earlier posting position. I see that during the hour or so of preparing this reply, many others have got in and posted a reply head of me. Not to worry though, they say the best comes last. 😆

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[Bigmandanc]

Wow, ok. Got a lot to digest. I'm going to go peco with electrofrog I think. I'm going to redo my scarm design in peco on Monday and reread this thread a few times haha. I can't thank you enough Chris. You and fish have been very very patient with me lol. I'm sure I'll have more questions later on.

Edit : As to the track, I only have 2 loops just now, mixture of Lima, triang and hornby so no worries there

Kind regards

Dan

[Bigmandanc]

One quick question, do you recommend the 75 or the 100 peco?

[Chrissaf]

If you were only going to use modern rolling stock with finescale wheels, then yes I would go with Code 75. If you need to support older DC Analogue locos (updated to DCC) and older rolling stock, then their wheel flanges may bottom out on Code 75. I'm using Code 100 Peco SL-E (Electrofrogs), Code 100 is more forgiving for older rolling stock. There is one thing that is available in Peco SL Code 75 that is not available in Peco Code 100. That is scissor cross-overs with Electrofrogs (of which your layout design has a few scissors).

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Since my layout is Peco Code 100, my scissor cross-overs are only available using insulfrogs. I had issues due to the geometry of the frog rails on these cross-overs of rolling stock wheels shorting across the opposing polarities. Since there was no Code 100 Electrofrog version I could replace them with [the Electrofrog would have eliminated the short circuit issue]. I ended up modifying my scissor cross-overs by isolating the frog area rails (cutting them with a Dremel), bonding the two opposing polarity rails electrically togther to emulate a psuedo Electrofrog and using a RLM (TamValley) to eliminate the short circuit issue. For information; the scissor cross-overs with the issue I had were Peco part number SL-94 (Long Crossover).

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If you are going to go with Electrofrogs, then I highly recommend that you go with an Accessory Decoder brand that includes frog switching contacts on the decoder. The Peco mechanical frog switches [PL-13] that you attach to the point motor (solenoid) are not the best [PL-15 switches are better but I find the plastic brittle and breaks too easily]. Also, you don't HAVE to use frog power switching on Peco Electrofrogs, but in my opinion it doesn't make sense to have access to an excellent reliability feature and not use it.

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Strewth ......only three paragraphs in this reply. EDIT: five if I include the PS's.

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PS - The geometry of the Peco SL track (only SL track have Electrofrog options) is completely different from Hornby track [Peco ST insulfrog track copies Hornby's geometry but ST track doesn't have any Electrofrog options]. The Points on Peco SL track are a lot longer than Hornby. You may find it impossible to 100% replicate your current design using Electrofrogs unless you increase the size of the baseboard by some considerable amount. The increased length of the SL points is further compounded by the fact that they produce track spacing of 50mm [this is too close for a small layout and could cause collisions where long carriages pass each other with their overhang on the curves]. To get the situation where two Peco SL points in a cross-over maintain Hornby 67mm track spacing for a smaller layout, you have to fit ST-202 straight Code 100 track pieces between the opposing points. The extra track length of the ST-202 extends the space needed for a cross-over even more. With SL track, there are only points, cross-overs and flexi-track. So if you go for Code 75, you can't use the Code 100 ST-202 track piece. This would need to be substituted with a short custom length of SL Code 75 flexi-track.

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PPS - If you didn't notice it before, follow the link to the Peco information in my last reply. This explains all the Peco track stock code numbering.

 

[Bigmandanc]

Awesome thanks. Even more to think about. I do have a lot of older rolling stock (40+ trucks so not cheap to replace, I have 3 old hst125 as well to convert haha) so I will go 100, and figure it all out once I've built it. I'll post a pic Monday with what I come up with and go from there. 

I'm forever saying thanks to you Chris lol.

Kind regards

Dan

[Chrissaf]

I think there may be a few edits in my last reply made after your last visit. Just posting this to bring possible edits to your attention.

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Taking the opportunity to add this drawing below, that might help you to visualise a simple DCC Bus connectivity solution:

/media/tinymce_upload/f5e718c6a8741d366122ffc2944ee20f.jpg

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[Bigmandanc]

Wow, that simplified it. I can see it in my mind now. Yet again, thanks Chris.

Dan

[Fishmanoz]

I think you should frame that one Dan and put it on the wall!

[Chrissaf]

Fishy, I think Dan should print out all the replies for framing....some of my best work....well at least after coming up with Plan B anyway......looking back at Plan A makes me think whatever was I thinking off when I came up with that one.

[Fishmanoz]

Good idea Chris. And no self flagellation necessary, reversing loops are tricky and your Plan A works after all, just not in practice with more than one train on the layout.

 

Advice on length of isolated sections should be a guideline of at least as long as your longest train, and not one inch longer.  We know this can be got around depending, like an HST with plastic wheels in the middle, but start with the guideline.  And a separate power district and booster for the part of the layout in your 2nd car space is just a reversing loop without the one inch longer guideline, and maybe without the RL.

 

That last statement about differences between districts and RLs needs some more thinking done about it too.  But another time.

[Chrissaf]

With regard Plan A, the outer loops would have been fine in the design, the track phase on both loops North and South would have all been the same all round the loops allowing multiple trains running round the loops in both directions without issue. The problem would have arisen when a train was traversing the North / South divide in the central area. That would have been when the RLM clashes would have occured, as I did document as the weak link in the plan.

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Once I did my Blue rail / Brown rail analysis of the central area. The Plan B solution became instantly obvious. I couldn't see it before, because of the sheer amount of track and route paths in the central area. It was definitely a case where for once "I couldn't see the wood for the trees" as my signature indicates I can, although I did in the end.

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[Bigmandanc]

Hi guys, due to a bout of sudden ill health, not been able to redo my display. When I am fit, I'll be back. Watch this space

 

Kind regards

 

Dan

[Chrissaf]

Sorry to hear that, I hope it is nothing too serious....get well soon.