Bus wire circuit

[HOTTODDY]

Hi folks, 

 

Could someone tell me what kind/amperage wire is needed for about 40 metre run of track please? e.g. solid or multi-strand and cross-section to give minimum power loss.

 

Thanks,

 

Tod

[amdaley]

Hi Tod.

Is that 40  metres / 130 ft  on a single track ?

What gauge are you using ?

Tony

[RAF96]

I use 2.5mm twin+earth ring main cable stripped out of the sheath to the two single insulated wires as my bus and I use Halfords stranded car acessory wire for the droppers (probably 5-amp).

 

Choice of cables based on what was in my spares box at the time and most suited to purpose.

 

Rob

[JST]

I have four  00 gauge mainline circuits plus a branch line of about 30 metres each. I run one bus per 2 circuits and have used 2.5m standard solid ring main wire. I wired each bus as in the radial arm fashion. No problems with power delivery but I had an intermittent signal issue until I fitted filters to the ends of the radial arms. Now runs perfectly. Your track length is slightly longer but 2.5 wire should be fine. 

[Crosland]

It's not how much track that matters but how long the bus will be. E.g. a linear 40m run of track will require 80m of bus wire. The same track squeezed into a 4-track oval would require much shorter busses and will cause much less voltage drop.

 

Having said that, the suggestion of individual cables stripped from T+E will cover most layouts. A portable layout would benefit form multi-strand cable of equivalent cross section. Soild core is fine for a layout that is not moved around.

[HOTTODDY]

Thanks for your input. I had intended to use cable from a redundant extension lead for a 00 single line to spiral round the loft space to a fiddle yard underneath the main layout. Radial wires can't be used, so the bus will have to follow either under or alongside the track, as its hidden from view anyway.

I have a confession to make in that the layout is DC and recent hot weather caused interruptions somewhere, (a dodgy rail joint or two very likely), so I thought best to ask the experts that use bus wire and droppers that give continuity. I believe the principal is the same, but the amperage is lower, but appreciate current loss is relevant over a long distance.

[Pete the Elaner]

You are not the only one to suffer a poor connection then decide to do things better next time.

Don't most of us do this?

[amdaley]

Never use rail joiners to carry power as over time they will eventually fail.

Power bus wire & droppers is the way to go and you can never have to many droppers.

[Junctionmad]

O Gauge DCC , 90 feet of DCC bus , 50/0.2mm no rail joiners at all , every section of track has a dropper , droppers are 16/0.2mm

 

I would not be a fan of using solid core at all

[Right Away]

Similar to that of RAFHAAA96, but utilised 4.0mm stranded on a linear 10 metre run.

It was the only sized cable I had spare at the time of installation, but it has proved faultless over the years.

As also mentioned, every individual piece of track, regardless of length is fed from the bus,

Edited June 1, 2018 by Right Away

[Andymsa]

What about soldering rail joiners ?

[Right Away]

What about soldering rail joiners ?

It might be OK for DCC on shorter lines but would negate the raison d'être of installing a low resistance under-board supply which virtually guarantees perfect data transfer as well as conductivity.

[JST]

What about soldering rail joiners ?

 

There can be issues with expansion and contraction of track due to temperature fluctuations.

[amdaley]

What about soldering rail joiners ?

 

 

There can be issues with expansion and contraction of track due to temperature fluctuations.

 

Resistance can build up in the rail joiners after a while which would lead to voltage drop & running problems.

[Marcyg]

There can be issues with expansion and contraction of track due to temperature fluctuations.

You could get round that using fuse wire omega loops. I’m going to have to use this method where I can’t fit a dropper due to under board space restrictions

[JST]

You could get round that using fuse wire omega loops. I’m going to have to use this method where I can’t fit a dropper due to under board space restrictions

 

Yes, I have done that on a hidden section.

[DCB]

Thanks for your input. I had intended to use cable from a redundant extension lead for a 00 single line to spiral round the loft space to a fiddle yard underneath the main layout. Radial wires can't be used, so the bus will have to follow either under or alongside the track, as its hidden from view anyway.

I have a confession to make in that the layout is DC and recent hot weather caused interruptions somewhere, (a dodgy rail joint or two very likely), so I thought best to ask the experts that use bus wire and droppers that give continuity. I believe the principal is the same, but the amperage is lower, but appreciate current loss is relevant over a long distance.

 

I have this issue outside.  Its sort of the same as DCC but different.  Basically any old mains lead will do for DC but I would go for 13 amp (ring main) wires in case you want to convert to DCC. Generally problems are caused by dodgy connections, screwed terminals and fishplates in my experience.  Fishplates especially,  We built the garden branch without a bus and its about 30 ish feet long and initially it worked very well, just fed from the shed. with frog polarity switches but no sections at the terminus.   After a bit fishplates started failing and random faults stopped play, usually after we run a loco into the frog end of a wrongly set live frog point and short everything out.  This causes a random fishplate to cry enough. so its out with the multimeter change the fishplate.   The first "Cure " was a lead to the terminus (TV Aerial lead) which took the load off the main line fishplates and limited the point related failures to the terminus. Next (completely useless) cure was soldering the fishplates, the rails buckled next time we had hot weather as there was no gap to take up the expansion. Next attempt was link wires round fishplates, the solder oxidised and they fell off after about 2 years, fishplates with wires attached were even less use when used correctly so now we are installing a pair of trackside Bus bars (13amp ring main wire) as the board is 18mm softwood. Guess what, the solder oxidises...  I wonder if fishplates with wires attached slid down a length of flexi  (Not at the end) might work better than soldering.  Soldering is so tedious so apart from a couple of additional feeds I rely on fishplates on the  inside layout, max run approx 20 feet ( 5 sets of fishplates) with almost no fishplate failures or unexplained slowings in 30 odd years

It is the maximum power, in Amps which does the damage, Once the fishplate has been over loaded and the connectivity lost then it has to be cleaned or replaced.  With DC this usually results from a short, (or ham fisted rail cutting leaving a "Burr")

I have had Rail joiners will glow with power from 2 X 1 amp controllers powering a triple headed train, which is only half the power of a typical DCC power unit so if using DCC I would use several power districts and use a 1 amp polyswitch as a "Re settable Fuse" in each to limit the max Continuous power and protect fishplates etc.