Double Track Operation in Dublo 3 Rail

[Wolseley]

I had some tracks set up on the dining room table this week to amuse our grandson (and me too of course).  It’s a fairly basic train set type design with a reverse curve, a siding or two and a turntable.  Yesterday I decided to try something a bit more adventurous for next week (we baby sit him three days a week).  After our daughter picked him up, I started adding a second oval of track (our dining room table is just wide enough for this) and joined the inner and outer ovals with a pair of manually operated isolating points.  This was the only connection between the two ovals.  Just to be on the safe side I put an isolating tab between the two points.  When I applied the power to either oval of track, I found that the locomotives on both ovals started to move at the same time.

 

This is the first time I have ever rigged up something that requires two locomotives to run at the same time independently of one another so, what with my lack of experience at running two trains at once and my rather basic understanding of electrics, I’m at a bit of a loss as to why it didn’t work properly.  Obviously something is not right, but I’m not sure what I have done wrong (unless there is something funny going on inside the controller).

 

I have attached photos of the underside of the points, to show what I did.

 

Can anyone explain to me what went wrong?

 

 

 

 

[Titan]

Are you using a single transformer with two controllers? It is possible on some controllers that are connected to the same transformer that the circuits will be common where they are connected to the transformer, and thus providing the connecting path. Duette controllers have one transformer, but a separate winding for each controller so they are not common and don't have this problem.

 

I am not so familiar with Dublo, but I have a suspicion that it might be worth trying to reverse one or both connections to the rails. However be careful as it might also cause a short circuit. Best bet is to try and use two separate transformers if you have them, or you could also insulate the outer rails and base at the joint if possible so there is no electrical connection between the two circuits on feed or return.

Edited April 21, 2017 by Titan

[TheSignalEngineer]

Can you please tell us what controller(s) you are using and a quick sketch of how they are connected to the track?

[sagaguy]

If they are Gaugemaster or Trax or similar electronic controllers,they need separate 16v ac transformers as this threw me for a while earlier this year when wiring my resurrected HD 3 rail layout after being used to Hammant & Morgan resistance conrollers.

 

                           Ray.

[Il Grifone]

The connections are 100% correct, so it can only be something dodgy in the controllers.

 

Even using a common supply, the operation of each circuit should be independent and only result in a short-circuit when one of the controllers is reversed, although there will probably be speed variations due to the common impedance.

 

Ideally one requires two separate supplies (or a transformer with two secondaries, though this still has common impedance problems). Because of the metal base, Dublo always has to be wired up with a common return - ideal for cab control.

 

As an aside,Trix is the same and all their accessories are designed to use the centre rail as a return. Unlike Dublo* the centre rail can be isolated if necessary.

 

* It is possible, but requires the use of insulated rail joiners or a specially modified track section.

[Wolseley]

Thanks for the responses so far.  I tried setting it up again, with the same result.  If I remove the points and replace them with straight track, both trains operate as they should.

 

Here is how the track is wired (bear in mind that this is a temporary set up on a table only at this stage).  There are no breaks in the insulation of the wires that run underneath the outer oval - in any case, I tested this by lifting up the track so that it wasn't touching the insulation, but the result was the same:

 

 

This is the controller I am using.  It is not a controller that I would choose to use, as I do not really like sliding controls.  It just happened to be sitting in a box in the garage unused since the 1980s, so if I can use it, it means I have a bit of money I can spend on other things.  The main reason I used it was that it was there already.  It seems to have an intermittent fault which may or may not have any bearing on all this.  It does at times emit a noticeable buzzing noise and very occasionally the power to the rails stops suddenly, although it is inevitably restored after a quick thump on the side of the controller - a wire inside touching something it shouldn't maybe?

 

 

[sagaguy]

Two things,the intermittent power supply is probably the sliders losing contact,common fault with linear pots.The other is that although it has outputs of 12v,it probably only has one transformer,no good for two track wiring.If you have a multimeter,set it to 200v DC & check that both centre rails are positive with the controller in the forward position.

 

                  Ray.

[sagaguy]

The connections are 100% correct, so it can only be something dodgy in the controllers.

 

Even using a common supply, the operation of each circuit should be independent and only result in a short-circuit when one of the controllers is reversed, although there will probably be speed variations due to the common impedance.

 

Ideally one requires two separate supplies (or a transformer with two secondaries, though this still has common impedance problems). Because of the metal base, Dublo always has to be wired up with a common return - ideal for cab control.

 

As an aside,Trix is the same and all their accessories are designed to use the centre rail as a return. Unlike Dublo* the centre rail can be isolated if necessary.

 

* It is possible, but requires the use of insulated rail joiners or a specially modified track section.

The beauty of Dublo 3 rail is that you can install cab control,ie.from outer track to inner using one controller can be wired through a single pole double throw switch.

 

                       Ray.

[kevinlms]

Thanks for the responses so far.  I tried setting it up again, with the same result.  If I remove the points and replace them with straight track, both trains operate as they should.

 

Here is how the track is wired (bear in mind that this is a temporary set up on a table only at this stage).  There are no breaks in the insulation of the wires that run underneath the outer oval - in any case, I tested this by lifting up the track so that it wasn't touching the insulation, but the result was the same:

 

20170422_073738.jpg

 

This is the controller I am using.  It is not a controller that I would choose to use, as I do not really like sliding controls.  It just happened to be sitting in a box in the garage unused since the 1980s, so if I can use it, it means I have a bit of money I can spend on other things.  The main reason I used it was that it was there already.  It seems to have an intermittent fault which may or may not have any bearing on all this.  It does at times emit a noticeable buzzing noise and very occasionally the power to the rails stops suddenly, although it is inevitably restored after a quick thump on the side of the controller - a wire inside touching something it shouldn't maybe?

 

20170422_073831.jpg

 

20170422_073818.jpg

Descriptions of the various models can be found here.

 

http://cdaelectronics.com/controllers/

 

These are later models, while it claims two trains can be independently powered, I'm not convinced that its suitable for common return layouts (which Hornby-Dublo is).

[Il Grifone]

Two things,the intermittent power supply is probably the sliders losing contact,common fault with linear pots.The other is that although it has outputs of 12v,it probably only has one transformer,no good for two track wiring.If you have a multimeter,set it to 200v DC & check that both centre rails are positive with the controller in the forward position.

 

                  Ray.

 

I would agree except that the centre rail should be negative with the controller in the forward position. Like 2 rail, forward is with the right hand running rail positive. ( This is why the polarity of the magnets is reversed between the 2 and 3 rail versions of Dublo locomotives.)

 

Slider potentiometers can often be serviced* by taking them apart and cleaning the muck of the track and slider contact and retensioning the latter. The dust seals work no better that on Brunel's atmospheric....

 

Some really cr rubbish components are beyond redemption (normally all plastic which doesn't appear to be the case here). 

 

A single transformer does not cause one control to affect the other (beyond slight speed variations), but will cause a short circuit if one is set forward and the other reverse. This can be resolved by isolating both circuits (all rails), but as I said before, this is a bit difficult with Dublo 3 rail. The rail joiners will come out with a little persuasion from a suitable screwdriver but then there is no location for the rails. I don't think most available insulated joiners will fit Dublo rail which has a rather large base. Possibly scale gauge 0 - they are both code 125 or thereabouts? Some tape would be needed to prevent the bases touching.

 

It looks like there is some sort of partial short between the outputs of the controller, but it's difficult to assess further at a distance

 

EDIT

 The presence of a single 2N3055 (good old standby!) power transistor suggests the outputs are not 100% independent. This would require two, one per circuit.

 

The cut-outs in the rail base are to take the wires feeding the inner circuit so that the track sits level. Dublo thought of everything (well almost).

Edited April 23, 2017 by Il Grifone

[sagaguy]

When i converted my Hornby 2BIL recently,the centre rail has to be positive or else  it ran in reverse.I first tested it on a length of 2 rail track with a multimeter with a positive RH rail before wiring the centre rail p/u.This has been checked on my 3 rail layout.With 3 rail locos,all run in the correct direction with a positive centre rail.I think you may be confusing it with Trix TTR which has a negative centre rail to allow twin running.

 

                   Ray.

[kevinlms]

 

EDIT

 The presence of a single 2N3055 (good old standby!) power transistor suggests the outputs are not 100% independent. This would require two, one per circuit.

 

 

Yes, of course that is the obvious giveaway. These CDA controllers have been around since the 1980's for sure & must be getting close to some sort of record, for longevity.

[sagaguy]

Although Gaugemaster handheld controllers work well with common return for two rail  with one 16v ac input,this didn`t work with 3 rail wiring.It took some Googling to realise that they needed two separate 16v ac transformers.I have recently purchased a Trax HH feedback controller which has a 1.5 amp output which keeps the trains running at a constant speed.

 

                     Ray.

[Il Grifone]

When i converted my Hornby 2BIL recently,the centre rail has to be positive or else  it ran in reverse.I first tested it on a length of 2 rail track with a multimeter with a positive RH rail before wiring the centre rail p/u.This has been checked on my 3 rail layout.With 3 rail locos,all run in the correct direction with a positive centre rail.I think you may be confusing it with Trix TTR which has a negative centre rail to allow twin running.

 

                   Ray.

 

Hi Ray,

 

Strange!

All mine run forward with the centre rail negative*, with the exception of my  Diesel shunter, rebuilt WC and one of my two Bo-Bo diesels. The first two are both converted 2 rail locomotives, but, not wanting to touch their ringfield motors, I left the magnetic polarity alone and so they run backwards. The Bo-Bo was deliberately set to run backwards so that I can double head them nose to nose (she has acquired a 2 rail D8017 body, but is original 3 rail). This is confirmed by the Dublo service sheets, which specify that 3 rail magnets should be reversed relative to the 2 rail version**. All my Tri-ang (and other) 3 rail conversions have needed their motor connections or magnet reversed.

 

Trix motors are A.C. (at least the early ones) so the polarity is irrelevant. The later D.C. ones go the same direction as Dublo. The problem with them is that, due to the centre rail being the common return for the Twin system, their chassis are live to the centre rail. This causes shorts with Dublo stock which is live to the running rails of course.

 

* Including the few that have their motors untouched.

 

** When I converted my locos to 2 rail in the early sixties (I only had half a dozen then!) , I insulated the LHS on some of them which must have been to ensure that they went the right way once converted. The Castle and 8F were (still are) insulated on the RHS, but I used the tender to pick up from the RH rail. All have been reconverted to 3 rail....

This was assisted by the change of heart on the part of Meccano Ltd. and making spare wheels etc. available. They weren't cheap for a schoolboy pocket, so only the absolute minimum of parts were used. The non-flanged wheels of the 8F were insulated with chrome tape for instance. (Some insulated wheels have been in stock for some time to finish the job properly but are still to be fitted....)

 

David

Edited April 23, 2017 by Il Grifone

[sagaguy]

Hi David,Ringfield motors are easy to reverse,just pull the magnet out slightly & rotate it 180°,i`ve not known a ringfield magnet to lose power,in fact,i have heard the remagnitising said magnet can cause it to lose strength,how true this is i don`t know.

 

                     Ray.

[Golden Fleece 30]

All Tri-ang (modern Hornby) have had to have their brush wires swapped to run the same as Dublo when 3-railed. The XO4 being dead easy by inserting the insulating sleeve and connector on the opposite side. There is no point reversing the magnets.

 

Garry

[DCB]

Its all to do with these new fangled controllers.   You want a pair of Marshall 3s or similar, proper 1950s technology. Or a pair of anything, not a double unit as all too often one circuit interferes with the other.

[Il Grifone]

Its all to do with these new fangled controllers.   You want a pair of Marshall 3s or similar, proper 1950s technology. Or a pair of anything, not a double unit as all too often one circuit interferes with the other.

 

Or an H & M Powermaster....

 

However these should be checked for old and tired insulation. At least one of my Marshall 3s had rubber insulation on the low voltage side (the one that needed repair and was opened). (Rubber has a 25 year use by date - long past....)

 

Avoid the Marshall 2, as it gives poor control in steps and all the other Dublo controllers as they are resistance controllers and suffer from the rubber insulation problem..

[Wolseley]

So it appears that the easiest solution to my problem is to replace the one controller I have with two separate ones.  It does mean spending some money, but I don't really mind that, as I want to be able to run two trains at the same time, and I don't really like sliding controls much anyway.  Also, in years to come, whatever layout I end up with will be likely operated by two people (it isn't at the moment, as my grandson is only 2) and having two separate controllers, aside from fixing the problem I have at the moment, would make operation by two people a bit easier.

 

I'm not too keen on buying second-hand controllers, especially if they are to be around 50 or 60 years old.  Are there any fairly basic (and hopefully it would follow that they are relatively inexpensive) controllers currently on the market that I should be considering?

[Il Grifone]

Hi David,Ringfield motors are easy to reverse,just pull the magnet out slightly & rotate it 180°,i`ve not known a ringfield magnet to lose power,in fact,i have heard the remagnitising said magnet can cause it to lose strength,how true this is i don`t know.

 

                     Ray.

 

Hi Ray,

 

I'm inclined to leave well alone (if it ain't broke...).

 

My Deltic came with a very tired magnet, but a new Neodymium cured that. My Co-Bo is a bit under par, but acceptable, so I won't touch her (she's still 2 rail ).

 

David

 

EDIT for errors - in a hurry - 'bus to catch

Edited April 24, 2017 by Il Grifone

[sagaguy]

Hi Ray,

 

I'm inclined to leave well alone (it it ain't broke...).

 

My Deltic came with a very tired magnet, but a new Neodymium cured that. My Co-Bo is a bit under par, but acceptable, so I won't touch her (she's still 2 rail ).

Co Bos are quite weird,i have two but unless you know that the Co end is forward,you`d never know,steam locos have that `oorible chimney at the front so anyone can see which way is forward!!.

 

 

                     Ray.

Edited April 24, 2017 by sagaguy

[Il Grifone]

Co Bos are quite weird,i have two but unless you know that the Co end is forward,you`d never know,steam locos have that `oorible chimney at the front so anyone can see which way is forward!!.

 

 

                     Ray.

 

The Co is first because that's the front end (unless you live on Sodor!   ). It's where the main radiators are situated usually.

Across the pond, it's usually the end with the cab. They also had steam locos with the chimney at the rear end (SP - I'd like one but they are rather large beasts). (So did the Italians - they were nicknamed 'Mucca' (cow) because of being 'milked' for expenses during trials. They were less than successful, but that is true of most Italian steam locomotives - short travel valves and congested steam passages).

 

I'd keep the existing controller for one track and add a second for the other. I think the cheapest one is the Hornby R.965 (IIRC). I don't know if it's any good. I rescued one from a bin at a boot sale, but not surprisingly it doesn't work. Currently it's in bits awaiting repair. There's not a lot inside, it's intended to work with a 'Wall-Wart' mains supply. I don't have the right one but have plenty of suitable substitutes. (I won't be using the Trix Twin transformer I have. It does work, but is a definite shock and fire risk. A pity really, as it's a substantial 3A device, intended to run two current hungry Trix locomotives and have a bit left over for accessories.)

Edited April 24, 2017 by Il Grifone

[kevinlms]

So it appears that the easiest solution to my problem is to replace the one controller I have with two separate ones.  It does mean spending some money, but I don't really mind that, as I want to be able to run two trains at the same time, and I don't really like sliding controls much anyway.  Also, in years to come, whatever layout I end up with will be likely operated by two people (it isn't at the moment, as my grandson is only 2) and having two separate controllers, aside from fixing the problem I have at the moment, would make operation by two people a bit easier.

 

I'm not too keen on buying second-hand controllers, especially if they are to be around 50 or 60 years old.  Are there any fairly basic (and hopefully it would follow that they are relatively inexpensive) controllers currently on the market that I should be considering?

In theory, it ought to be possible to buy 2nd hand controllers that AREN'T 50 to 60 years old. The main problem with most of that vintage, is that they have resistance mats (poor speed control) or else have dodgy mains cords.

 

Many people have upgraded to DCC, so there should be many transistorised controllers available. Most are not self contained, but require a separate power supply (easiest to use plug packs).

 

Ones to avoid are some entry level controllers, these often came in train sets. Usually the owners didn't care about smooth running, as long as trains ran FAST!

[sagaguy]

It seems that trying to get a controller for operating HD 3 rail on seperate circuits is a bit of a minefield these days.Looking around the net,it seems that there are not any controllers with two sepeate transformers which is what is needed.The only answer seems to two seperate transformers wired to two handheld controllers such as Gaugemaster model HH or aTrax HH which to my eyes is preferable because it has a 1.5A output.I have two H&M controllers which are used so supply 16V AC to my handhelds.

 

                Ray.

[cessna152towser]

I've been to a few shows with Hornby-Dublo 3-rail and set up a double track oval with connecting points and an insulating tab between the third rail connector tongues beneath the points, like the set up you have posted.   I always use two separate transformers and have never had any problems with electrical interaction between the two circuits.

Edited May 7, 2017 by cessna152towser