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> Hornby Three Rail controller., How to power a 3-rail layout with several sections.
WEE
post 17 Mar 2010, 21:29
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I recently brought my boyhood Hornby Dublo 3-rail trains from England. Everything is still in excellent condition so I want to set it up again and play trains.
I wish to have in inner and an outer loop so that I can run two trains independently of one another but I also want to be able to run from one loop to the other via two points (or switches). I would also like to have a shunting yard with a third controller.
As far as I can recall, when Hornby used this configuration they simply put an isolating tab between the sections and were able to run each one independently with no problems.
I originally had a home made controller which gave me individual control of each track but if used with just an isolating tab between the loops a short circuit occurred. My father overcame this problem by making a special piece of track which, in combination with an isolating tab, totally isolated one loop from the other.
If I use my modern 2-rail controllers I am sure that I am going to run into problems because the metal rail provides a continuous circuit everywhere and a two rail controller simply reverses the polarity.
One answer would be to use 24v dc and a rheostat with a center tap at 12 volts supplying the outside rails. The wiper on the rheostat would deliver from +12 volts dc to -12 volts dc relative to the outside rails and one controller would not interfere with the other.
Unfortunately, in the modern world of transistor controls, a rheostat able to handle the wattage is difficult to find and the cost is prohibitive. Also, importing old controllers from England, because of the weight, would be extremely expensive. (Although a step up transformer from 110 v ac to 220 v ac is surprising cheap).
Can anybody tell me a way of solving this problem (cheaply) or give me an idea of how Hornby managed it please?
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hoonsou
post 18 Mar 2010, 03:50
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I would have thought that three rail wiring is pretty close to dcc wiring. For crossing over from one loop to another, wouldn't you use isolating rail joiners, or the equivalent on all three rails. ? Then as long as both controllers were set to the same polarity, there'd be no problem.... or have I completely misunderstood the question.


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WEE
post 18 Mar 2010, 05:37
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Many thanks for the reply.

The problem is that there is no way of isolating the outside rails from one another, the fish plates are permanently mounted to the metal base of the track.

My father overcame the problem by cutting a 1/4 straight in half and rejoined it by riveting a piece of insulating material across the gap. I then used an isolating tab and the two circuits were permanently isolated from one another.

Unfortunately, when using large radius and standard radius curves in the two loops, the rails come so close together that there is no space for the special piece of track.

Once again many thanks for the reply. Maybe your suggestion will trigger an idea from somebody else.
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Saint Johnstoun
post 18 Mar 2010, 08:09
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I can't see any difference between wiring up three rail and the common return system I use on my two rail layout. One rail is continuous and fed with up to five controllers, whilst the other is broken into sections and fed from various outputs. The important thing is that every controller must have a separate transformer winding - its no use taking a 12v feed off a power unit with only one transformer winding.

I use the old H&M stuff and it works fine. I think that all you need to do is to isolate the centre rails and make sure you feed the outer rails with power from a separate winding for each track.
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34C
post 18 Mar 2010, 09:30
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Hornby managed it exactly as Saint Johnstoun describes. Provided independent transformer windings are used for each controller, adding the insulating breaks in the centre rail make it a common return wired sectioned system. This was one of the great strengths of three rail, it made the wiring very easy. Your Dad's home brew controller, because the input was commoned by reason of all the controller channels taking power from the same transformer winding, inevitably requires full isolation of all the rails and the conducting track base, to create separate sections. There is no escape from that.

Before going any further, I have a suggestion to make. The locos will probably still run beautifully given a little TLC. Unless you are very lucky the track will be the limiting factor in running reliability. H-D's wheel profile was very close to RP25, and the trains will run perfectly well on a code 100 track system like Peco's streamline, with the nickel silver rail giving you much better continuity. For sure you have to add a third rail yourself, but what you get in return is a layout with complete flexibility in curve radii, and much larger point radius in a larger selection of points. I have seen a few carefully maintained H-D show layouts, and they require non-stop tinkering with the track to keep them operating. Which is fine if that is what you enjoy: but the last such exhibit I saw, while in conversation with the owner he told me that modern track was what he used at home, because he wanted trouble free running. This is very much a personal taste thing, but it is an option to keep in mind if reliable operation on the original track proves a problem.
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Saint Johnstoun
post 18 Mar 2010, 12:13
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Its nearly 50 years since I had Hornby Dublo 3 rail but if I remember rightly the A3 power unit I had featured three outputs. Output A was 12v DC controlled, Output B was 12v DC straight, and output C was 16v AC from a separate transformer winding. If you wanted to run a second train then you bought a separate controller which took its input from the 16V AC output, and gave you another 12v controlled output.

The points I had were Isolating ones if I remember rightly, but you still had to put a little fibre isolating tab between the centre contacts if running double track.

You could also buy isolating rails, which had a break in the centre third rail and two screw terminals which you connected to one of Hornby's switches.

I seem to remember that somebody tried to connect a battery controller to the uncontrolled output of an A3 power unit and came across the same problems as WEE has.
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kiwionrails
post 18 Mar 2010, 12:59
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I think peco do a 'contact strip, link designed for this sort of purpose biggrin.gif , i'm thinking about getting some so i can run some of the 3rail locos that i was given.

Regards

Kiwionrails


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....and who said i was too young.

Cameron Dalziel

Just another teenager playing with trains. :)

My website Kiwi on Rails
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34C
post 18 Mar 2010, 15:14
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The contact strip is designed for use with Marklin system stud contact collectors, which is the big remaining maker of a (very good) three rail system. It is a lot more discreet in appearance than having a third rail. I have been told that to make Hornby Dublo run with this, many locos need a small modification to provide a larger collector skate area. I would try asking around on specialist sites like that of the Hornby Railways Collectors association to see what information they have.
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Saint Johnstoun
post 18 Mar 2010, 16:36
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I saw it done years ago. The Hornby 3 rail locos had two collector shoes back to back and what had been done here was to connect the two with a brass strip which effectively clipped over the existing shoes and made a skate long enough to bridge a number of studs. The layout involved I saw at an exhibition somewhere and used Peco track. Brass pins were simply driven into every 5th sleeper and connected by a copper strip mounted under the track - on curves this was more awkquard as wire had to be used. The layout if I remember had both 2 and 3 rail tracks on it but each part was kept separate. You cannot, of course, run 3 rail locos on 2 rail track even with a 3rd rail or studs in place as the wheels are not insulated. I also knew somebody with a Trix Twin layout who had insulated drivers fitted to some of his Hornby locos so he could run them on this system but I never actually saw it in operation.
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WEE
post 18 Mar 2010, 17:03
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To Hoonsou, Saint Johnstoun, 34c and Kiwionrails,

Many thanks for the generous information.

You were absolutely right: my controller did have only one transformer and, in addition, one very large selenium rectifier and one hand wound resistance with 4 fixed tappings supplying both tracks. The box also had a "black crackle" finish that was cured in the kitchen oven.

In our defense, I should say that we were machine tool fitters and not electricians. Although my father did have access to an almost unlimited supply of scrap and obsolescent electrical equipment from the company in North London where he worked.

I hope that I will shortly be able to put your information to the test and will report back.

I do have a Hornby 2 rail project which has stalled because of the difficulty in getting the older items to run on modern H0 rails. I have successfully reworked a Princess Coronation and have started to modify the rolling stock. (This may be the subject for a later enquiry).

I have also vacillated for several months over the power supply. It seems that everybody here in California has changed over to DCC and this is quite a large investment.

I thought that my 3 rail project could be more easily brought to completion so that I would have something to play with.

Once again, many thanks for the generous gift of your time.



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br1972
post 18 Mar 2010, 20:21
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As the proud owner of a Hornby Dublo 3 rail layout...see My Layout perhaps I could add a few comments.


QUOTE (Saint Johnstoun @ 18 Mar 2010, 19:09) *
I can't see any difference between wiring up three rail and the common return system I use on my two rail layout. One rail is continuous and fed with up to five controllers, whilst the other is broken into sections and fed from various outputs. The important thing is that every controller must have a separate transformer winding - its no use taking a 12v feed off a power unit with only one transformer winding.

I use the old H&M stuff and it works fine. I think that all you need to do is to isolate the centre rails and make sure you feed the outer rails with power from a separate winding for each track.


Saint Johnstoun is absolutely on the button here! In fact the best explanation I have come across is to be found on Steve Chapman's Railway pages on wiring a common return...Common Return Wiring...All that is necessary is to insert insulating tabs between the third rail joiners at the place where two controllers... having their own independent transformers... sections meet, for example at a crossover. If you don't have the proprietary tabs as supplied by Hornby, thin card works equally well.

QUOTE (34C @ 18 Mar 2010, 20:30) *
Before going any further, I have a suggestion to make. The locos will probably still run beautifully given a little TLC. Unless you are very lucky the track will be the limiting factor in running reliability. H-D's wheel profile was very close to RP25, and the trains will run perfectly well on a code 100 track system like Peco's streamline, with the nickel silver rail giving you much better continuity. For sure you have to add a third rail yourself, but what you get in return is a layout with complete flexibility in curve radii, and much larger point radius in a larger selection of points. I have seen a few carefully maintained H-D show layouts, and they require non-stop tinkering with the track to keep them operating. Which is fine if that is what you enjoy: but the last such exhibit I saw, while in conversation with the owner he told me that modern track was what he used at home, because he wanted trouble free running. This is very much a personal taste thing, but it is an option to keep in mind if reliable operation on the original track proves a problem.


In my experience whilst the locos do need TLC, replacement of the original magnets with modern neo magnets, widely available on e-Bay, help to give trouble free running.

As for track, whilst it is possible to remove 50 years of grime from original track using elbow grease, isopropyl alcohol, masonite board, etc...the weak links..so to speak..are the original fishplate joiners...it is just about impossible to remove accumulated dirt...so replacement with Peco SL-10 joiners is the go. I have also added a few more feed in points compared with the original...

After that the locos run better than when new...So WEE hope that helps...the Old Hornby Dublo really is fun and brings back the childhood memories... thumbsup.gif

Cheers
Geoff rolleyes.gif
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Saint Johnstoun
post 18 Mar 2010, 22:20
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I remember that the insulating tabs were expensive and got a whole sheet of similar stuff from our local TV repair shop for about half the price of a packet.
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WEE
post 22 Mar 2010, 13:47
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IT WORKS!!

I have put together two loops with a crossover pair of points. I am using a TECH II Dual Power controller with a home made isolating tab and I have got everything that I wanted.

However, it still feels as if I am getting something for nothing or that I have contravened one of Newton's laws. But what the heck. The Silver King, with two puny looking tin-plate coaches, is once more circulating at a scale 250 mph, the 2-6-4 tank seems to be quite happy and I will shortly be bringing The Duchess of Montrose out of its box.

Since posting this query, I have received helpful advice from 5 different people, have been put on to a very relevant article by a Steve Chapman and have seen pictures of a very impressive layout on the other side of the world. Quite an amazing few days.

Many thanks to everybody for all the interest and help.





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TerryB
post 22 Mar 2010, 14:42
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As another proud owner of a [small] Dublo layout ....may I just say ... wink.gif
How much I have enjoyed reading this thread ....even if I could not answer with any advice ... unsure.gif
Anyways "WEE" .... wink.gif .....hows about some pics please .... dribble.gif

best regards
Terry
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Saint Johnstoun
post 22 Mar 2010, 15:45
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Great - think of what it was like even 20 years ago let alone 50! You now get help and encouragement instantly - almost and the information can be shared with so many other folks.

Enjoy your Dublo! I've moved on but it is so nice to see that others are keeping it alive.
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