Correct cable choice?

[teaky]

I am seeking guidance (confirmation) of the choice of cable for layout wiring please.

 

I have trawled through responses to similar questions and can't quite satisfy myself regarding the answer. 

 

Key facts:

- DC not DCC

- 00 bullhead

- largish roundy-roundy in the region of 25m circumference

- bus wires

- droppers from each piece of rail

- permanent layout split into 12 baseboards with connectors between each so that a baseboard can be removed to work on it.

 

Is 16/0.2 multistrand copper the correct choice?

 

Will this be too bulky to solder to bullhead making 7/0.2 a better choice for the (short) droppers?

 

Will 16/0.2 be sufficient for the bus or would I be better with 32/0.2 ?

 

The idea of just having a single gauge of cable is appealing.  I would not need to have several reels in use, not need to ensure I selected the correct one each time and, possibly, not need to use different connectors.

 

Edited June 23, 2019 by teaky
correction

[sharris]

What sort of trains will you be running and what kinds of motors do they have?  the likely current drain of your engines under load will govern the thickness of the wiring you need

 

Here's a link to a data sheet from Farnell with the characteristics of one of their cable systems from 16/0.2 upwards. 

 

http://www.farnell.com/datasheets/1230998.pdf

 

Looking at data sheets for 7/0.2 cable they are rated 1-2amps - unless you're using old greedy motors  I'd probably use that for droppers and something more meaty for the bus to reduce the voltage drop over the length of the bus.

[Free At Last]

 

1 hour ago, teaky said:

 

- largish roundy-roundy in the region of 25m diameter

 

Will give a circuit of around 80m(metres?)

[teaky]

37 minutes ago, Free At Last said:

 

Will give a circuit of around 80m(metres?)

Doh!  Original post corrected.  Thanks.

[teaky]

1 hour ago, sharris said:

What sort of trains will you be running and what kinds of motors do they have?  the likely current drain of your engines under load will govern the thickness of the wiring you need

 

Here's a link to a data sheet from Farnell with the characteristics of one of their cable systems from 16/0.2 upwards. 

 

http://www.farnell.com/datasheets/1230998.pdf

 

Looking at data sheets for 7/0.2 cable they are rated 1-2amps - unless you're using old greedy motors  I'd probably use that for droppers and something more meaty for the bus to reduce the voltage drop over the length of the bus.

Mainly RTR.

 

I'll take a look at that link.  Thanks.

 

[cliff park]

One or two things to remember. Cable ratings tend to be for when they are in sheathed enclosures or conduit. In free air they can handle much more. If you have droppers from every piece of rail they are all effectively in parallel, the current carrying capacity is enormous. The in-built safety margin means you could use very fine wire, but in reality there is no point. There are advantages to using single core for the droppers:- ease of soldering to rail being the main one.

[teaky]

44 minutes ago, cliff park said:

One or two things to remember. Cable ratings tend to be for when they are in sheathed enclosures or conduit. In free air they can handle much more. If you have droppers from every piece of rail they are all effectively in parallel, the current carrying capacity is enormous. The in-built safety margin means you could use very fine wire, but in reality there is no point. There are advantages to using single core for the droppers:- ease of soldering to rail being the main one.

I have been looking at the cpc.farnell.com website and the only solid core cable I can see is standard twin and earth typically used for domestic lighting circuits with the smallest being the 1mm².  This seems a little chunky for droppers.  Is there something you recommend please Cliff ?

[teaky]

3 hours ago, sharris said:

What sort of trains will you be running and what kinds of motors do they have?  the likely current drain of your engines under load will govern the thickness of the wiring you need

 

Here's a link to a data sheet from Farnell with the characteristics of one of their cable systems from 16/0.2 upwards. 

 

http://www.farnell.com/datasheets/1230998.pdf

 

Looking at data sheets for 7/0.2 cable they are rated 1-2amps - unless you're using old greedy motors  I'd probably use that for droppers and something more meaty for the bus to reduce the voltage drop over the length of the bus.

Does the 16/0.2 qualify as "meaty" in this context?

 

Sorry if this sounds pedantic but I've only ever wired up small shunting layouts previously and used some very skinny multistrand cable of unknown gauge soldered to a few key locations with power transfer via the rails and fishplates.  This worked fine but what I have in mind this time is much more ambitious and I'm keen to get it right and to avoid voltage drop whilst not going completely over the top.

[cliff park]

I actually use odd lengths of internal telephone wire, after all you are only looking for short lengths. Failing that old scart cables stripped out have a surprising amount of wire, very small wire size, but a lot of it multiple strand. I must admit to never throwing away any wires or cables, old chargers, USB leads, anything which may be stripped down and reused.

[teaky]

Very fine then.  Thanks Cliff.

[sharris]

16 hours ago, cliff park said:

There are advantages to using single core for the droppers:- ease of soldering to rail being the main one.

 

Possibly a disadvantage of using single core though - a single solid core is less flexible than multi-strand  - it's normally used to connect things that don't move. If your track flexes, or your single core cable is not secured to a solid fixture, it is more likely to break at any bends (and you'll probably need a bend to solder it under the rail and then pass it through the baseboard) than a multi-strand cable.

 

[5050]

Don't solder direct to the rail.  I use an 'L' shape piece of brass wire approx. 0.5mm thick pushed down through a small hole adjacent to the rail and soldered to the rail web on the side away from the viewer.  Very discreet.  The wire under the board is then bent again 'L' and the end soldered to a small brass screw fixed about half to one inch away.  Any connections can then be made to this, even multiple ones, without affecting the rail connection above.

[Junctionmad]

I suggest for 00 feeds should be a minimum of 7 strands of 0.2 tinned wire 

 

I would not reccomend solid core. 

 

No issues soldering 7 strand to the bottom of an OO rail 

[rogerzilla]

The best size for bus wire is the biggest that will fit into the back of your controller.  This isn't particularly big on my Gaugemaster DS.

[Dave John]

Well, if you want enough 7/02 to last a lifetime buy a drum of 8 core alarm cable. less than 20 quid for 100 m drums, as an electrical contractor I get it for half that. 

 

I'd also agree with junctionmad . its easy to solder discreetly to the bottom of the rail. 

 

spot the droppers ........ 

 

 

 

[teaky]

After pondering the advice above, additional reading and further searching I have concluded that I am more convinced by the flexible droppers approach and that the inconvenience of using two types of cable is insignificant.  So, for the record, I am going to purchase some 7/0.2 for the droppers (in the form of 6-core alarm cable) and some 16/0.2 for the bus.

 

Thank you to all for the advice.  Even if I didn't follow your suggestion, at least I know why I made that decision.

[Poor Old Bruce]

I would go for 1/0.6 for the droppers, soldered to the rail foot/web. It's easier to form into place and hold while soldering. Don't worry about flexing as once it's in it shouldn't get waggled about at all, even with heat expansion. Try and get a dropper to each and every piece pf rail. do nor rely on rail joiners for electrical conductivity. Then use 16/0.2 for the main runs.

[sharris]

6 hours ago, teaky said:

So, for the record, I am going to purchase some 7/0.2 for the droppers (in the form of 6-core alarm cable) and some 16/0.2 for the bus.

 

 

Should be fine. Don't forget to spec the connectors though - you say you have 12 boards with power connectors from one to the next (that's quite a lot of connectors!), so make sure that they can handle the current and have low contact resistance. 

 

The only caveat would be - you say you are running DC - if there is any likelihood of you ever changing your mind and switching to DCC (like when you count up the connectors you might need for all the buses!)  on this layout, you might want to up the bus spec. 

[steve W]

6 hours ago, Poor Old Bruce said:

I would go for 1/0.6 for the droppers, soldered to the rail foot/web. It's easier to form into place and hold while soldering. Don't worry about flexing as once it's in it shouldn't get waggled about at all, even with heat expansion. Try and get a dropper to each and every piece pf rail. do nor rely on rail joiners for electrical conductivity. Then use 16/0.2 for the main runs.

I concur with using a  single strand for the droppers. Entirely adequate due to the short lengths involved. Have used this on 0 scale without problems and far less intrusive than stranded wire. Attached to the bottom of the rail before laying if possible. The current carrying capacity of the wire is entirely dependent on it's length and the volt drop that results from the resistance of the wire.  Two or three inches of the small dropper wire is irrelevant and your decison should be based on ease of fitting and obtaining a neat appearance.

Beware of some data cables and alarm cables  -they are often made of aluminium and will not effectively solder.  In supplier specs this will be noted as CCA (copper coated aluminium) there is also copper coated steel that has the same problem, though much less common. I also reccomend using tin/lead 60/40 solder rather than lead free for the same reason.

[teaky]

2 hours ago, sharris said:

 

Should be fine. Don't forget to spec the connectors though - you say you have 12 boards with power connectors from one to the next (that's quite a lot of connectors!), so make sure that they can handle the current and have low contact resistance. 

 

The only caveat would be - you say you are running DC - if there is any likelihood of you ever changing your mind and switching to DCC (like when you count up the connectors you might need for all the buses!)  on this layout, you might want to up the bus spec. 

I am intending to use connectors like this at baseboard joints.  They come in a range of sizes and shapes.  They are rated at 32A & 400V.  I don't know what the resistance is.  They appeal because it would make it easy to unclip cables prior to removing a board to work on it but it is a fixed layout and this ought not to be a frequent occurrence.

 

DCC is unlikely and I have not looked into the technical aspects.  I suppose it would be sensible to at least consider the impact.  The data sheet you posted earlier in this thread indicates 16/0.2 cable is rated at 3A.  What rating would DCC require?

 

[RobjUK]

That cable rating chart is strange! The 16/0.2 we us is rated at 11A...

http://www.doncastercables.com/product-documents/TRI-RATED.pdf

 

The cable resistance is more important than the current rating from model railway use; the longer the run, the more voltage is lost in the cable for any given load. For a large layout, go up a size or two from what appears to be required. For a very large one, go up four times or more.

 

Using DCC does not directly affect the cable requirement, if you were running the same loco as under you were under analog control.

The change with DCC is that you can run two, three or more locos in the same power zone, and it's likely you will end up doing that if you go to DCC. That's where you need heavier cables, to allow for running multiple locos simultaneously.

 

With your 25m layout, I'd use at least 1mm, possibly solid core mains cable (eg. twin & earth style, with the outer stripped off). That's also quite easy to spot-strip with a small pair of wire cutters, to connect droppers.

 

 

 

 

[teaky]

Slightly ironically, before making the original post, I had thought of using 1mm twin & earth (T&E) for the main runs but found the multistrand cable idea appealing because of the extra flexibility of the cable.  I know that a number of RMwebbers use T&E, it is still reasonably flexible, especially once the outer sheath is removed, and I don't anticipate making and breaking connections too frequently so it should be easy enough to work with.  Toolstation have a good deal on the Doncaster Cables 1mm T&E at the moment meaning that I can get a 100m reel for £29 with free delivery, so as a bonus I'll also save money relative to the alternative solutions.

 

So that's the main bus sorted.  I'll use 1mm T&E.

[teaky]

Now: droppers.

 

Again, prior to starting this thread I had thought that single strand would be easier to work with but decided that the flexibility of multistrand provided insurance against breaking.  My reasoning was that breakage might result from movement and that movement might come from three sources:

  i  manual bending as part of the fitting and fixing

 ii  baseboard movement in general from temperature changes, seasonal moisture and human clumsiness

iii  movement of the track - ballasted but on top of 3mm foam.

 

I have soldered thin multistrand to the underside of code 100 rail previously and it wasn't too difficult but it definitely wasn't neat (i.e. nothing like Dave John's photo).  With such a large number of droppers to solder I can see the appeal of single strand.  Making a neat job seems easier but are my concerns regarding movement unfounded or not?

[RobjUK]

I'd stick with stranded for the droppers, personally.

 

Strip, tightly twist and tin the 7/0.2 first and cut any excess off the tinned section; the cheap alarm wire seems to have low grade insulation that shrinks back rather more that most other cables when you solder it..

 

Then treat it as stiff single strand & bend the end at 90' with pliers, if appropriate for how it will be positioned.

Tin the track first then add the wire to the pool of solder, or re-heat while holding the dropper end in the correct place, until the joint has fully flowed.

 

If you try and solder directly to untinned rail in one go, it's likely to be far messier. It's not a good idea with two things that need such radically different amounts of heating.

 

If you go for single strand, I'd try to arrange the joints so the wire runs parallel to the track before bending downwards, even if only for a few mm, plus not attaching it to the baseboard too close to where it goes though, so any slight movement can be taken up over some length of wire rather than all the stress being on one spot.

 

Not rigidly fixing with wire in the baseboard where it goes through really applies to any droppers I suppose, as if its glued it's bypassing the function of the foam bed and passing noise and vibration to the baseboard, as well as stressing the wire - track joint.

 

Edited June 28, 2019 by RobjUK
typos

[hobbyhorse]

I'm a bit belt and braces when it come to wiring. For my ON30 layout which is quite large I've used 16/0.2 for the droppers with short runs to the connector blocks, each section of rail has 2 droppers,  from these the baseboard internal wiring is 24/0.2. Then the main bus is 32/0.2. The rail code is 83 so quite a small size with the droppers soldered to the bottom which becomes invisible once ballasted. The layout is designed for operations with upto 8 people required, and lots of locos on the layout requiring quite a lot of power. Hope this helps.

 

Edited June 28, 2019 by hobbyhorse
Correction