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chaz

DCC bus - is this a good idea?

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I wonder if anyone can suggest any reason why I shouldn't do my DCC bus like this...

 

P1050278-2%20800%20x%20440_zpspppebarw.j

 

  • the bus wires are tinned copper wire (uninsulated) fixed to the support legs at the back of the layout
  • they are separated vertically and are kept apart with light timber spreaders
  • bus wires are wound around round-headed wood screws
  • bus wires can be terminated at intervals with solder tags
  • The droppers from the rails (each piece of rail will have its own dropper) are insulated multistrand
  • the droppers are soldered to the bus wires

I would welcome suggestions about what gauge wire to use for the bus

 

I should say that the layout is fixed - not portable - and track will be laid across baseboard joints. I am keen to avoid the need to work on the underside of the baseboards to do the wiring.

 

Chaz

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Possibility of accidental shorts from miscellaneous metal things that get placed adjacent to the bus under the layout? - Unless you guarantee you're never goung to put anything under the layout.

 

I think I would always go for an insulated wire, that can identify black and red, and cut into the insulation to make connections, even though it's probably more of a pain.

 

Peter

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Hi Chaz,

 

I used to be very anti until I realised that all dcc layouts have exactly this set up in the most vulnerable place it's called track.

 

So go ahead.

 

Cheers 

 

Godders

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Depending on the size of the layout, the idea may prove to be inconvenient.  If, for example it is an 8' x 4' board with a continuous run, you would either have long droppers running from the front of the board to the bus on the back, or you would have the bus also on the front of the layout.  Any track in the centre of the layout would also have long droppers if the bus is only at the edge of the layout.  Long droppers crossing the underside of the boards could be a nuisance.

 

Harold.

 

An alternative (if you really want to avoid wiring underneath the boards) is to solder a short piece of flexible wire to the outside of each rail, across every rail joint - ie duplicating the work of the rail joiner.  It has to be done after the track is laid rather than, for example, soldering droppers to the bottom of the rail before it is laid.  Thus, as Godders said, using the track as the bus but not relying on the rail joiners for electrical conductivity.

Edited by HLT 0109
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If your layout is indoors, in a well insulated modern, dry house this will work well. If there is any reason for the timber to absorb moisture then I'd be concerned about leakage current through the timber.

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Hi Chaz,

 

I used to be very anti until I realised that all dcc layouts have exactly this set up in the most vulnerable place it's called track.

 

So go ahead.

 

Cheers 

 

Godders

Which will be fine as long as Chaz has never had a short from random things left on the track,- and that's when you can see the exposed elements, not hidden under the layout - if he has, he's just as likely to get the same again, only this time it won't be as apparent. :)

 

To me it's counter intuitive to build in a potential risk when it could be designed out, I can see little down side of using insulated wire that's identifiable as correct polarity, but lots in using bare wires with 16V running through.

 

 

 If there is any reason for the timber to absorb moisture then I'd be concerned about leakage current through the timber.

 

Again it's unseens like moisture from above (ballasting, spillages etc) that are potential risks of this event happening, not sure what protection is on Chaz's DCC but I have previously fried a DCC booster because no-one noticed the little red light and there was no audible warning or cut-out.

 

https://en.wikipedia.org/wiki/Murphy%27s_law

 

Peter

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Possibility of accidental shorts from miscellaneous metal things that get placed adjacent to the bus under the layout? - Unless you guarantee you're never goung to put anything under the layout.

 

I think I would always go for an insulated wire, that can identify black and red, and cut into the insulation to make connections, even though it's probably more of a pain.

 

Peter

 

I can guarantee that I will put things under the layout!   But anything close to the bus can be in cardboard boxes. I did use insulated wire on my aborted first attempt at an On30 layout and, you are right, cutting it away was a pain.

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Hi Chaz,

 

I used to be very anti until I realised that all dcc layouts have exactly this set up in the most vulnerable place it's called track.

 

So go ahead.

 

Cheers 

 

Godders

 

Yes, Godders, I had that thought too, however track with its fixed rails is less likely to give problems..... oh hang on what about the idiot who runs into the back of a point set adverse. No you are quite right.

 

Chaz

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Which will be fine as long as Chaz has never had a short from random things left on the track,- and that's when you can see the exposed elements, not hidden under the layout - if he has, he's just as likely to get the same again, only this time it won't be as apparent. :)

 

To me it's counter intuitive to build in a potential risk when it could be designed out, I can see little down side of using insulated wire that's identifiable as correct polarity, but lots in using bare wires with 16V running through.

 

 

 

Again it's unseens like moisture from above (ballasting, spillages etc) that are potential risks of this event happening, not sure what protection is on Chaz's DCC but I have previously fried a DCC booster because no-one noticed the little red light and there was no audible warning or cut-out.

 

https://en.wikipedia.org/wiki/Murphy%27s_law

 

Peter

 

You make a couple of very good points. Insulated wire it is! Cutting the insulation is a pain and the soldered joint where the dropper is fixed is going to be difficult to insulate - but the bare wire will be a very small area. Something like this...

 

P1010600a%20600%20x%20510_zpsuikdp39b.jp

 

Chaz

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Depending on the size of the layout, the idea may prove to be inconvenient.  If, for example it is an 8' x 4' board with a continuous run, you would either have long droppers running from the front of the board to the bus on the back, or you would have the bus also on the front of the layout.  Any track in the centre of the layout would also have long droppers if the bus is only at the edge of the layout.  Long droppers crossing the underside of the boards could be a nuisance.

 

Harold.

 

An alternative (if you really want to avoid wiring underneath the boards) is to solder a short piece of flexible wire to the outside of each rail, across every rail joint - ie duplicating the work of the rail joiner.  It has to be done after the track is laid rather than, for example, soldering droppers to the bottom of the rail before it is laid.  Thus, as Godders said, using the track as the bus but not relying on the rail joiners for electrical conductivity.

 

Thanks for that Harold. In fact the layout will be 14' x 10' all round the outside of my roof space with no board wider than 2'. The fiddle yard has been wired more conventionally, with the buses running on the underside of the boards - but these were put upside down on a Workmate to do the work. I can't do that with the scenic boards.

 

It's not wiring under the boards I want to avoid, it's working upside down!

 

I don't like putting link wires across rail joints - IMHO it's not pretty and certainly doesn't fit in with hand-laid spiked track.

Edited by chaz

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Thanks lads for those ideas, very helpful. I will give some further thought to the problem. At present I am spiking rail and every piece/length has a dropper usually soldered to the joiner which is itself soldered to the rail end.

 

Chaz

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I used to be very anti until I realised that all dcc layouts have exactly this set up in the most vulnerable place it's called track.

 Bare wires DCC bus in use for thirteen years now. Not once had a single problem arising. The ease of just soldering on another dropper, or a point feed to a manual point switch is advantage enough to persuade me, even if the odd short did occur. If it is a challenge to recognise the right one consistently, thread on coloured beads, or put on colour coded tags of insulating tape. If postioning under the layout put them close to the front of the layout, for easier access. Leakage current: the bus wires are threaded through metal screw eyes straight into timber. The roof developed a leak in winter while I was away and the timber was well soaked by a week of downpours, no problem. (I have seen current leakage enough to significantly affect operation, about four metres of double track all wet with the 'spray on dilute PVA' ballast securing technique - not a problem due to having exposed bus wires - and it didn't stop operation, just slowed things down as the track voltage sagged under the demand.)

 

In what I am building now, I am going to go a step further on the non-scenic sections, bare bus wires on top of the boards, copper tapes under track to supply the droppers. Trialled it and no problem arose. As Godders above: one quickly learns that the rails are not the place to put down the metal tools, and the rails will be shorted out before anything contacts the bus wires.

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 Bare wires DCC bus in use for thirteen years now. Not once had a single problem arising. The ease of just soldering on another dropper, or a point feed to a manual point switch is advantage enough to persuade me, even if the odd short did occur. If it is a challenge to recognise the right one consistently, thread on coloured beads, or put on colour coded tags of insulating tape. If postioning under the layout put them close to the front of the layout, for easier access. Leakage current: the bus wires are threaded through metal screw eyes straight into timber. The roof developed a leak in winter while I was away and the timber was well soaked by a week of downpours, no problem. (I have seen current leakage enough to significantly affect operation, about four metres of double track all wet with the 'spray on dilute PVA' ballast securing technique - not a problem due to having exposed bus wires - and it didn't stop operation, just slowed things down as the track voltage sagged under the demand.)

 

In what I am building now, I am going to go a step further on the non-scenic sections, bare bus wires on top of the boards, copper tapes under track to supply the droppers. Trialled it and no problem arose. As Godders above: one quickly learns that the rails are not the place to put down the metal tools, and the rails will be shorted out before anything contacts the bus wires.

 

Thanks Hatfield, it is always a big help when someone speaks with authority informed by experience. Putting the bus wires close to the front is very appealing. I don't think there will be any challenge involved in identifying two colours - no need for coloured beads! - on the FVRR orange is the far rail, green the nearer but I haven't painted the rails those colours! In the same way underneath if I decided that the top bus is orange and the lower green then this will be consistent right round the layout. Labelling will not be necessary as every dropper wire will be so coloured. Should I need to check as I solder a dropper I only need look at the last one.

 

Although I did use insulated wire on the earlier (dismantled) version of the FVRR it was a pain stripping the insulation from short sections so that the droppers could be soldered - see my photo in my earlier posting. Bad enough doing this on the bench, but underneath the boards....  :nono:   I did look at insulation displacement connectors but decided that their long-term use might not be as reliable as required - certainly not as trustworthy as soldering.

 

Your comments about moisture are apposite. I am spiking rail through balsa ties into the plywood trackbed, and my ballast, weeds etc will be fastened with dilute PVA. Once this has dried I know there should be no problem (FVRR Mark 1 was done this way). A leaking roof? In that case the railway would stay firmly off until the leak were fixed and the effects dried out.

 

Chaz

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You could make life a bit easier and only use insulation on one conductor. If it's a large layout, you might want to include some isolation switches to help with fault finding.

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Although I did use insulated wire on the earlier (dismantled) version of the FVRR it was a pain stripping the insulation from short sections so that the droppers could be soldered - see my photo in my earlier posting. Bad enough doing this on the bench, but underneath the boards....  https://www.rmweb.co.uk/community/uploads/emoticons/default_nono.gif   I did look at insulation displacement connectors but decided that their long-term use might not be as reliable as required - certainly not as trustworthy as soldering.

Easy stripping of insulation in the middle of a wire needs the right tool ! I've used these, it really does strip (push the insulation back) in the middle of a piece of wire to allow a soldered joint, just like the photo in post #9 higher up the thread.

 

http://www.rapidonline.com/Tools-Equipment/C-K-495001-Automatic-Wire-Stripper-85-0002

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You could make life a bit easier and only use insulation on one conductor. If it's a large layout, you might want to include some isolation switches to help with fault finding.

 

I like the idea of isolation switches. On my Dock Green exhibition layout in the event of a fault each board can be isolated by simply disconnecting the bus connecting cable. Something similar on the FVRR will be installed.

 

Chaz

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Easy stripping of insulation in the middle of a wire needs the right tool ! I've used these, it really does strip (push the insulation back) in the middle of a piece of wire to allow a soldered joint, just like the photo in post #9 higher up the thread.

 

http://www.rapidonline.com/Tools-Equipment/C-K-495001-Automatic-Wire-Stripper-85-0002

 

Thanks for that link, Nigel - very useful!  If I do decide to use insulated wire (and that is looking more likely now) I will certainly invest in one of these.  (Strange - I knew of this tool but never thought of it to bare a section in the middle of a wire..... "It's your age, dear!")

 

Chaz

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Thanks for that link, Nigel - very useful!  If I do decide to use insulated wire (and that is looking more likely now) I will certainly invest in one of these.  (Strange - I knew of this tool but never thought of it to bare a section in the middle of a wire..... "It's your age, dear!")

 

Chaz

 

The only time they don't really work is if there is insufficient run of wire either side to "take up the slack" and sometimes the break will close up before you can get the dropper attached.

 

If you are careful you can make two breaks followed by a longitudinal slit to remove a collar of insulation.

 

I use the blue and brown conductors stripped from 2.5mm^2 solid core mains cable. The insulation is more "brittle" and cuts and strips very easily.

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wiring-system-1-800.jpg

 

I do something similar, except all my wiring is on top of the baseboards, to save my crawling underneath

 

The two DCC bus wires are bare 22 swg running along either edge of the wide track base. I don't think they are visible in this shot.

 

Cross feeds are flat 0.001" brass shim at 9" intervals, soldered to alternate bus wires. The individual rail feeds are short bare 30 swg wires, tacked onto the appropriate nearest cross feed.

 

ballast-hides-wire-800.jpg

 

After ballasting, all the wiring is invisible, including the side busses. But the positions of the cross feeds can be marked, just in case of any future problems arising.

 

Andy

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The only time they don't really work is if there is insufficient run of wire either side to "take up the slack" and sometimes the break will close up before you can get the dropper attached.

 

If you are careful you can make two breaks followed by a longitudinal slit to remove a collar of insulation.

 

I use the blue and brown conductors stripped from 2.5mm^2 solid core mains cable. The insulation is more "brittle" and cuts and strips very easily.

 

Thanks for that helpful advice. I think I am close to a plan! The remaining decisions relate to where exactly to put the bus and how to support the wires. No rush to decide as there is a lot of nice modelling to do before I need to do the wiring.

 

Chaz

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Just as a final thought, a 'half-way-house' solution occurred to me last night.

 

Run bare wires in small conduit

 

http://www.screwfix.com/p/tower-self-adhesive-mini-trunking-25mm-x-16mm-x-2m/64026

 

then by just drilling a small hole in the top you can pass wires into the trunking and solder up. The wire will pull out to connect and push back in when connections are made. Once completed the front capping can be attached to tidy it up. It's not expensive, effectively adding the insulation but retaining the ease of access and connection?

 

Peter

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Just as a final thought, a 'half-way-house' solution occurred to me last night.

 

Run bare wires in small conduit

 

http://www.screwfix.com/p/tower-self-adhesive-mini-trunking-25mm-x-16mm-x-2m/64026

 

then by just drilling a small hole in the top you can pass wires into the trunking and solder up. The wire will pull out to connect and push back in when connections are made. Once completed the front capping can be attached to tidy it up. It's not expensive, effectively adding the insulation but retaining the ease of access and connection?

 

Peter

 

Nice one! I like that idea, a good way of keeping everything neat and tidy. I will of course use two lengths of trunking - not a good idea to have both bare-wire buses in close proximity in trunking  :nono: .

 

Chaz

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Wires stripped from twin and earth, connect droppers with scotchlock connectors (100 for a tenner), job done. :)

Edited by ZiderHead

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Wires stripped from twin and earth, connect droppers with scotchlock connectors (100 for a tenner), job done. :)

 

Thanks. Do you have a supplier or a link for scotchlock connectors?

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Part of my layout is 4ft from the front edge, although my power bus runs along the front installing it round the end was a no go.

I have done exactly what you have done works fine. I used stripped house hold lighting wire, and used plastic terminal blocks to secure it.

32g wire was used to connect to the main bus.

Yes I use this space to store items out of the way, its no trouble to make sure nothing fouls the wires.

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