Voltage drop - can I get her around the track

[Lb101]

Hi all, my first post, some great advice out there, hello all.  I have a question.

I bought a DC set for my little boy and set it up in our attic.  I have loads of space up there and have become hooked and have big plans!  Building a town and wish to lay track all the way around the room for the Mallard.  Infrastuctur already underway.

I'm not interested in digital (at this stage anyhow), I wish to keep it analogue, and now have two sets which I got at reduced price, and therefore two R8250 single controllers.  The small West Highland express for the approx. 1.5m x 4m town planned and then I'm adding track that extends through the town and then around the room for the Mallard (about 6m x 5m) using narrow shelving/insulation board and large corners which will become towns/seaside towns.  There will be a very slight incline up at one point and then down again to get over the roof Truss's (plenty of space to make this slight).

Will the standard R8250 get it around or do I need to wire it up somehow at points around the track, basically like a ring main with power at few places around the track coming from the controller.  My question is, is this viable and if so how would I wire it?  The basic R8250 unit and power track don't have anywhere to solder from and to. Could I use a R8012 HM2000 Power Controller instead? Many thanks for any advice on how to make this work.

[Chrissaf]

The R8250 controller power supply is very low current capability. Enough current for a couple of modern locos at best. Will struggle to operate even a single loco of an old design that requires more current. The R8250 also overheats quite quickly and shuts down until it has cooled off.

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If you have an R8012 HM2000 that is a much more capable controller with plenty of oomph. Given a choice I would use a single R8012 over two R8250s any day.

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"Do I need to wire it up somehow at points around the track, basically like a ring main with power at few places around the track coming from the controller."

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A very good plan and absolutely worthwhile doing. Then you won't be reliant so much on the push fit track joiners to distribute power. It only takes a couple of loose joiners to stop a loco dead in its track (pun intended).

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You could use R602 power clips, but my preference would be to solder the power wires directly to the OUTSIDE edge of the rail. Don't solder to the inside edge of the rails as the soldering may foul the wheel flanges of your rolling stock and cause derailments. The wires soldered to the track are called 'droppers'. The 'droppers' are connected in turn to a pair of thicker wires that distribute around the layout under the baseboard. The thicker wires connect to the output of your controller. If you are using twin R8250s or a R8012 dual controller, then you will need four thicker under board power distribution wires, two per circuit. Make sure the droppers of the two track circuits are connected to the relevant under board power distribution pair. Use colour coded wires so that you do not cross over the polarity from one rail to the other, else you will get a short circuit. Also use colours to identify the two separate power distribution circuits.

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To maintain correct distribution polarity as you wire the layout, you could use the wagon method. Put a piece of sticky tape on one side of a wagon. Push the wagon around the layout NEVER LIFTING IT OFF. When the wagon gets to a position where you want to connect a dropper. Choose a dropper wire colour (say Red for example) and only solder Red wires to the rail that is associated with the taped side of the wagon. As long as the wagon never leaves the track then it is impossible for the Red wire to be connected to the rail associated with the NON taped side of the wagon. If the other wire colour is Black for example, then only solder Black wires to the rail associated with the NON taped side of the wagon. If you follow this procedure you will avoid any inadvertent short circuits being accidentally introduced.

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Although you are not using Hornby Track Extension Packs or following a Hornby TrakMat layout plan, you may still benefit from reading my "Getting Started with Track Extension Pack" document (link at the top of the forum General Section). Section 5 of the document focuses on DC control. It also gives part numbers for the insulated rail joiners etc.

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Bear in mind as a DC layout, you will need to allow the electrical switching feature of your points to control the power going into sidings. If you connect the sidings directly to your DC power distribution bus then you will need to include some electrical switches so that you can isolate power from the sidings. If you don't, you will have nowhere to park your locos when not running round the main track circuits.

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Also, bear in mind that if using twin R8250 controllers or a dual R8012 controller. There will be TWO track power distribution circuits. These TWO track power distribution circuits need to be electrically isolated from one another by using insulated track joiners. Read my document for more information on this design requirement. Typically, two ovals of track. One oval of track per controller output. Insulated Rail Joiners are used on the points that face each other where there is a crossover from one oval to another. Its all covered in my downloadable document.

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PS - My reply is a long wordy reply. if you want to make a reply to it. Please DO NOT click the 'Blue Arrow' quote button embedded at the bottom of my reply. Instead scroll down to the bottom of the page and type your reply in the great big empty text reply box and click the Green 'Reply' button. Clicking the 'Blue' button will duplicate the whole of my text in a large yellow text box unnecessarily. 

 

[Lb101]

Many thanks Chrissaf for you thorough reply.  I'm looking forward to setting this up and learning a bit more about the electrics to boot.  I've know about insulating the two tracks from one another but on the sidings set up, are you saying don't use droppers to the sidings and everything will be OK (as the TrakMat layout works), or does the fact I am distributing power around the circuit at various points mean I need to isolate them (I can't get my head around this)?

My main question is how do I link the controller output wire (which has no bare wire and a plug at the end) to the thick circuit wires than will run around the track?  This is probably a very simpistic question but just looking for reassurance before I take the action I think I have to take i.e. do I simply cut the wire and solder the bare parts to the 'thick' track wires (polarity won't matter at this stage apart from the trains forward mode might be the oppostie to what I want whereby I can simply switch it, unless it's possible to ascertain this by plugging it in the the power track prior to cutting and seeing the direction of travel).  Apologies if this makes no sense.  Many thanks for the explanation and great tips, I will read your document link!

best wishes

[Chrissaf]

Splitting your follow up reply into separate questions.

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Question 1) Sidings.

In a DC layout, the loco moves whenever power is applied to the track. If you make a direct connection from the siding tracks to the distribution wires running under the baseboard, then the siding will be always connected to the controller output. Thus any loco sitting on the siding will try to move when the associated controller is turned up.

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The moving rails of the point act as electrical switches. When the point is in the straight ahead position, there is no power being routed to the siding and any loco sitting on that siding will remain stationary. When you switch the point towards the siding, then the moving rail makes contact with the power rail and power is applied to the siding. This power switching feature will be circumnavigated if you connect the siding track to your under board distribution via 'droppers'. For the majority of sidings this is not an issue and you can just rely on the rails and their metal joiners for electrical continuity. If you wanted to provide additional power connections to the sidings for reliability (see note below), then the droppers would need to incorporate make break electrical switches in conjunction with insulated track joiners to allow the power to the siding to be manually isolated when you want to park a loco there.

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Note: The electrical switching action of the point relies upon physical contact between the moving and fixed rail (side contact of the rails). The side of these rails need to be kept clean and in good working order, else the electrical continuity through the point can become intermittent.

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Question 2) Controller Connections.

On the R8012 Dual controller, the power connections on the rear of the controller are via spring loaded press tab terminals. These will accept bared wires. Thus with this controller you can discard the Hornby provided power wires and power clips altogether and just connect your under board distribution wires directly to the controller.

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On the R8250 controller, the output wires are terminated internally within the controller and end on a two pin plug. There are two options:

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1. Cut off the plug and make a join by either sleeved soldered joint or screw down terminal block or similar to the under board distribution wires.
2. Alternatively, if a screw down terminal strip of the right size is chosen (the electrical white nylon variety you can get anywhere...B&Q for example). Then the two pins of the plug may fit into two of the screw down holes and the base board distribution wires can be screwed down on the opposite corresponding side. This connection option gives the advantage that if the loco travel direction is wrong, then the connector can be easily unscrewed and reversed. As using a terminal strip in option 1) above would do too. This option has the additional advantage that by not cutting off the connector, any outstanding controller warranty is maintained.

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Question 3) Direction of Travel.

If the direction of travel made by the loco is reversed compared to the position of the controller direction switch. Then just reverse the connection of the distribution wires terminated on the rear of the controller. Provided the layout is wired up using my wagon tip. Then the loco direction of travel will remain consistent throughout the whole layout.

[Gordonvale]

My layout is 8m x 6m, circuits being 24m - 25m. In real life each is split into 4 sections with its own non-Hornby DC controller powered by a lab supply. A while back whilst "playing" I tried the Pendolino set controller on a full 25m single circuit with the wires merely jammed against the rails in a single spot; it worked just fine. I suggest for starters you'll be fine using your Hornby controller, properly connected at just one spot. Whether this is suitable or not will be dictated by your layout geometry.

The "industry standard" for polarity is: +ve on the inner rail of an oval runs a loco clockwise.

[Lb101]

Many thanks for all your help guys.  All taken on board and crystal clear.  I think mine is about 20m so I can see how I get on with a test period before I start sticking/pinning stuff down.  I can go into it with a bit more confidence now, thanks again.

[dadad]

Hi there,

 

it is usually a good idea to look at brian lambert's pages for information if you are unsure.  He can be found at http://www.brian-lambert.co.uk/, always worth a look.

 

John 

[Lb101]

It's been a while but my layout is now up and running afte a load of joinery work (messy). A little shorter than the 20m I said (it's about 15m). I bought the Hornby hm2000 and its running like a dream without droppers/bus wire. Got a load of second hand track and cleaned up with a modelling sander (one of those things that rotates at speed). Thanks for your help John, Gordonvale and especially Chrissaf. Started with scenery and lights now. Getting to know Ohms law, great fun running analogue!

[poliss]

You should never use anything abrasive on track. It will make tiny scratches which collect dirt.

Use lighter fluid on a cloth or kitchen towel to clean track if it'd really dirty, then keep it clean with the rough side of a piece of hardboard.

[Lb101]

Thanks poliss. I had read about that. I made a beginners mistake of getting the track down and working then realised how dirty it was compared to my new pieces of track. It was a light touch and you could see the rail turning from black to silver (steel track). I then lightly sanded, used the Hoover to pick up the dirt and added some brasso Followed by a damp cloth. Probably not the best method as you said but  my loco was stalling at a couple of points but now is running well. I've bought a Peco track rubber which will hopefully smooth it out A bit, and tor idea of hardboard is taken onboard. Thanks

[poliss]

If you're going to use track rubbers I think most prefer the Hornby one to the Peco one.

[trainlover23]

Thanks poliss. I had read about that. I made a beginners mistake of getting the track down and working then realised how dirty it was compared to my new pieces of track. It was a light touch and you could see the rail turning from black to silver (steel track). I then lightly sanded, used the Hoover to pick up the dirt and added some brasso Followed by a damp cloth. Probably not the best method as you said but  my loco was stalling at a couple of points but now is running well. I've bought a Peco track rubber which will hopefully smooth it out A bit, and tor idea of hardboard is taken onboard. Thanks

One should never mix steel and nickel silver track. You could get voltage drop problems or complete failures.

For mainline circuits always use nickel silver track

[37lover]

trainlover23,

Is there scientific reasoning behind that or is it just from observations & experience?

[trainlover23]

trainlover23,

Is there scientific reasoning behind that or is it just from observations & experience?

There is a scientific reason but I can`t remeber it but it is common knowledge in the modelrailway world

[Fazy]

Are we talking about 'Galvanic Corrosion" where one metal acts has a Anode will the other act like the Cathode. Where the Anode is attacked and corrodes. 

[Fazy]

Could be the other way round.  It's a while since I did this in Physics.