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Few questions regarding the use of a DCC bus


Richard Croft

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I'm currently building a new railway and I'm slowly getting together all the things I need. I'm using peco electofrog code 75 track and I will be using traintronics motors. I have just bought a 15m solderless DCC bus kit off ebay. My Questions are; I know the point motors connect to this and the track feeds go through them to the points, including the polarity control. on these I can solder to where I add the new jumpers. But I'm wondering if for the rest of the track it is acceptable to connect wires to the fish plates rather than the track itself? It somehow seems a little easier. I was also wondering what the best way to connect the bus cables to the bottom of the board is, if it helps its made from 9mm mdf.

 

Last question, Am I best incorporating some insulated rail joiners for when I install signals now or should I just cut the rails once the layout is operational and I have a better Idea where I'm going to put them?

 

Thanks In advance, Richard

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I'm currently building a new railway and I'm slowly getting together all the things I need. I'm using peco electofrog code 75 track and I will be using traintronics motors. I have just bought a 15m solderless DCC bus kit off ebay. My Questions are; I know the point motors connect to this and the track feeds go through them to the points, including the polarity control. on these I can solder to where I add the new jumpers. But I'm wondering if for the rest of the track it is acceptable to connect wires to the fish plates rather than the track itself? It somehow seems a little easier. I was also wondering what the best way to connect the bus cables to the bottom of the board is, if it helps its made from 9mm mdf.

 

Last question, Am I best incorporating some insulated rail joiners for when I install signals now or should I just cut the rails once the layout is operational and I have a better Idea where I'm going to put them?

 

Thanks In advance, Richard

 

Hi Richard.

Easier is not always best. It is not a good idea to use fish plates/rail joiners to get power to your layout as over time resistance will build up between the track & rail joiners leading to poor power distribution & frustration.It is best to solder drop wires to the underside of the rails & I would suggest every section of track or if using flexible track at least every 36" also test every connection when you have made it for continuity.

To run the bus cables you can drill holes in the cross members of your baseboards or use eye hooks & feed the cables through them. You can also buy cable hooks which have a sticky back to fix to the underside of any surface.

If you are creating signaling/block sections it would be easier to mark them out on your plan & use the insulated rail joiners as you lay the track. If this is not convenient simply cut the rails with a Dremel or similar tool when you know where you want these breaks & the track has been fixed to the baseboard.In that case you won't need insulated joiners as the track is unlikely to move when fixed down.

Depending on how you plan to operate these signaling/block sections take care how you join them to the main DCC bus as the droppers to such sections might have to join a DCC sub bus before joining the main DCC bus especially if you plan some type of block arrangement.

If you have more questions just ask.You will always find someone has an answer.:)

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Thanks for the replies, that's a lot of droppers to solder to the rails, (a technique I'm yet to master!) The hooks idea is good for the wire to go through and not something I would have thought of, I need to keep the wires close to to the board as my layout will sit on castors to slide under a bed. As for signalling I have given it very little thought, I just know that I'll control some of the ones on my station and ones with feathers using the Traintronics point motors. Thanks for your help though, it's made me feel like I can atleast start the job!

 

Richard

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. But I'm wondering if for the rest of the track it is acceptable to connect wires to the fish plates rather than the track itself? It somehow seems a little easier. I was also wondering what the best way to connect the bus cables to the bottom of the board is, if it helps its made from 9mm mdf.

 

Last question, Am I best incorporating some insulated rail joiners for when I install signals now or should I just cut the rails once the layout is operational and I have a better Idea where I'm going to put them?

 

Thanks In advance, Richard

 

I have used the metal rail joiners for dropper feeds without problems. I think the reason that people counsel caution is that some of these railjoiners are made of a different metal to the rail itself and with current flowing through the joint, electrolytic corrosion might occur particularly if there is any condensation present. There is also the settrack syndrome in that rail joiners are loosened by being joined and pulled apart.

 

Just make sure that you use the joiners intended for your track and make sure they are tight. You would also do well to make absolutely sure that any cut rail ends are dressed with a file before installing the joiner. I also drilled them so that the dropper wire is vertical.

 

I used Maplins self adhesive pads with cable ties through them for holding cable runs under the baseboard. They don't stick that well to MDF so in the case of heavier cable runs a dob of glue helps and of course one can add extra pads and ties at will. The best alternative is staples but you will need an industrial grade stapler.

 

From my experience with block detectors, which is mainly watching someone else build a demo layout incorporating them, I think it best that you just cut the rail after the signal is sited.

 

From what I saw, only one rail is cut and, unless it is close to another pre existing rail joint, there is little need to use insulated railjoiners anyway. The cut is usually just beyond the signal and as the loco transits the cut, the signal changes.

 

Traintronics do them along with the signals.

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It's definitely not 'best pracrtice' to use fish plates as the connection point for DCC droppers.

 

Fish plates provide a means by which expansion and contraction in the rail itself can be accommodated without the track buckling. Unfortunately this continual sliding motion causes a build-up of oxides within tge fish plate which iduces a resistance between the fish plates and the rails.

 

In addition to this there is a good chance that during track ballasting and weathering a certain amount of glue, paint and other general crud will find its way into the fish plate which can only be to the detiment of a good electrical contact and good running.

 

Rough the bottom of the rail with a fine file and tin it with a small amount of solder. Tin the end of the dropper wire and then bring them together with the soldering iron and a tiny bit more solder for no more than 2 seconds. "Simples".

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Thanks for the replies. I think I will solder the wire directly to the track then. I don't want to create problems later. Would the filing/tining/2 seconds method apply to the dcc modifications for electrofrog points too?

 

Thanks for the info about signals too. I suppose if I just cut the rail that way I can have it exactly where I want instead of having to go to the nearest joint, I'll look into the Traintronics stuff. Having read up about their point motors it seems like their products make things pretty straight forward compared to other makes

 

Richard

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Thanks for the replies. I think I will solder the wire directly to the track then. I don't want to create problems later. Would the filing/tining/2 seconds method apply to the dcc modifications for electrofrog points too?

 

Yes that's correct Richard. It is always better to pre-tin the two pieces you are going to solder together.

Thanks for the info about signals too. I suppose if I just cut the rail that way I can have it exactly where I want instead of having to go to the nearest joint, I'll look into the Traintronics stuff. Having read up about their point motors it seems like their products make things pretty straight forward compared to other makes

 

Richard

 

You should fix droppers approximately in the centre of every individual piece of track, irrespective of how long or short it is.

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Thanks for the replies. I think I will solder the wire directly to the track then. I don't want to create problems later. Would the filing/tining/2 seconds method apply to the dcc modifications for electrofrog points too?

 

Thanks for the info about signals too. I suppose if I just cut the rail that way I can have it exactly where I want instead of having to go to the nearest joint, I'll look into the Traintronics stuff. Having read up about their point motors it seems like their products make things pretty straight forward compared to other makes

 

Richard

Using the rail joiners is fine if you then solder them to the rail. The trick is to only solder them to one rail so that the other one can still move to allow for expansion. Always solder the same end of each piece of rail, so that each piece of rail has one soldered joint and one sliding joint.

 

Andrew Crosland

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Using the rail joiners is fine if you then solder them to the rail. The trick is to only solder them to one rail so that the other one can still move to allow for expansion. Always solder the same end of each piece of rail, so that each piece of rail has one soldered joint and one sliding joint.

 

Andrew Crosland

 

 

The problem with this is that it forces the rails to expand in one direction only which they obviously don't. This can cause track to buckle

 

I can never understand the people who try to find 99 alternative ways of doing it instead of just following the one way of doing it right :angry:

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The problem with this is that it forces the rails to expand in one direction only which they obviously don't. This can cause track to buckle

 

I can never understand the people who try to find 99 alternative ways of doing it instead of just following the one way of doing it right :angry:

 

I took the trouble to check the coefficient of expansion of nickel silver at room temperature up to boiling point. It is 9 MICROinches per 1 degree Fahrenheit.. I will leave the mathematicians among us to calculate what temperature range is needed to make a metre of rail expand by 1 mm which is probably the least gap in a rail joiner and the longest length of rail between rail joiners.

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A coefficient of expansion should not have any units of length, only of temperature, as it gives the amount of expansion relative to the original size. Google finds me a value of 16.5 parts per million per degree C. 1mm gap in a yard length is just less than 1000 parts per million so would allow for a temperature difference of 60 degrees C.

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Unfortunately the mathematics does not tell the whole story.

 

Add to that the effect of resistance caused by both rails having to simultaneously expand/slide through every chair along each rails length (instead of only half of them) and bearing in mind the added effect of paint, glue etc. on the rails ability to actually slide through the chairs anyway and there is a distinct possibility that the track will buckle.

 

I'm sorry but there is just no sound arguement for attaching droppers to track joiners other than 'can't be bothered to do it right'.

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The problem with this is that it forces the rails to expand in one direction only which they obviously don't. This can cause track to buckle

The rail can still expand both directions. At one end it slides in the chaie. At the other end the soldered chair moves with it.

I can never understand the people who try to find 99 alternative ways of doing it instead of just following the one way of doing it right :angry:

I prefer to think things through for myself, rather than blindly follow what others say :)

 

Andrew Crosland

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