3 Rail Conversions

This section includes Gaiety, Graham Farish and Trix Twin engines. All of these engines are contemporary with HD. The newest being the first one we look at.

Up until 1994 I had basically collected and run Hornby Dublo and Wrenn Locos some of which had been repainted and re-bodied. Looking back, my first “modern” loco was a Trix-Lilliput model of The Flying Scotsman.


Now Trix have been around throughout the period of Hornby Dublo and after from before the war until the current times but they have been the subject of many owners, many systems and even scales. Trix Twin started as a 3 rail system but a different 3 rail to HD. The track was bakelite based and had a

centre pickup rail and two other rails were  separately earthed. This meant that two trains could run  on the same track. Trix also had very large wheel flanges which made them completely unsuitable for running over HD points. The post war versions also had the option of fine scale wheels which made them suitable for HD track. This particular model was after Trix had been bought by Liliput and is an OO model. Many of the earlier Trix models some of which I have and are shown below are HO scale or even intermediate between the two.  You can also read ‘A brief history of Trix‘ written by Model Railway Express.

After the Express Locos I focused on Tank Engines and small tender engines. So next came the GWR built o-6-2T in BR livery from Trix Twin. This is supposedly a HO model but its size is very close to the HD N2 loco so I have always thought of it as close to OO gauge. This is a genuine Trix 3 rail loco with slight modifications to the loco pickups to enable it to run very well on HD track.

The next loco is the Trix model of theSouthern E2 loco and this is definitely in HO scale it is also plastic unlike the diecast one above. This is a 2 rail engine which has been converted. Small but a nice little runner with a single or a couple of carriages. It is in late BR logo livery with no number. I think this means that it has been fiddled with at some time because it should have a number.

The final Trix engine is a BR Standard 5MTtender engine with a very heavy diecast body making it an excellent runner although it has been converted from 2 rail. The paintwork is a bit tatty but overall it is an impressive engine.

Now we move onto Gaiety Engines made by Castle Arts of Birmingham They only made a model of a GWR Pannier Tank and their version of the N2 tank engine. My one has an original 3 rail chassis which means that it is a bit noisy and slow but runs and it does look the part. I also have another one with a modified body and running on a HD 0-6-0T chassis. It has been re-painted, not that well, into BR black. The extra weight of the body much improves the running of the HD 0-6-0 chassis.

Finally in this section we have another GWR Panier tank engine, a different series to the Gaiety ones, but this time made by Graham Farish. This company started in OO gauge in the 50’s and produced a good range of models including some tender engines with a shaft drive from the tender to the engine. This was very complicated and there are few that have stood the test of time. This tender engine is in excellent condition and a great runner, it was probably converted to 3 rail from new.


This section includes Triang, Airfix, Mainline and Hornby engines all produced in 2 rail but converted to run on my 3 rail layout. The majority are tank or small tender engines to fill the gap left by HD in their meagre tank engine line up. There might just be an Express passenger engine or two but they are always interesting and liable to be added to the layout.

Before we start with my locos lets get the history of Triang out of the way.

In other words they were the total enemy of HD – no HD collector would consider Triang (cheap plastic trains) and vice versa (expensive old fashioned 3 rail). But time has passed, the rivalry has cooled and Triang had some interesting engines plus EMUs and DMUs so it was always worth exploring possibilities of 3 rail versions of their engines.

If we go back to the prototype railways of the 50’s and 60’s we find that BR tried very hard to keep branchlines viable and therefore open to traffic by substituting steam with diesel rail cars. The chronology of events in BR provides a very useful and brief overview of the many things that happened during the BR reign. Thus a Triang DMU fits well into the time period in which Dublo exists. Also the Southern Region of BR had a vast network of 750V three rail electric lines with large numbers of EMUs both on commuter services to London and long distance services to Southampton and Bournemouth. Later the Hastings line was dieselised freeing up steam engines like the Schools class and replacing them with DMUs. The Triang EMU I have is a two car version but Triang did make a centre car allowing it to be a 3 car or even a 4 car unit. Hornby Dublo also had an EMU which was introduced very nearly at the end of HD and is thus very rare and therefore very expensive. I make do with the Triang version. Both of these conversions seem to be a bit tricky and I have to admit neither of  these models run very well.

Lots more to add in this section but not of the greatest interest to Hornby Dublo collectors.

I was asked in the comments to post some pictures of the types of pick ups used for conversion from 2 rail to 3 rail. So here goes.

The first one is a

Hornby M7 converted

using a Marklin full size skid.

Then we have a Hornby London Transport Pannier Tank converted using springy metal with cups on the ends.

  A Triang Jinty uses a similar system.

A Graham Farish 0-6-0PT, same idea but execution is a bit grim.


The basic springy metal pick-up as seen on an Hornby N2

A Trix 0-6-0T with an original pick-up.

The conversion of the HD 2 rail 0-6-0T shows each possibility

Above we have the official conversion using two small HD pick ups

Then we have the Marklin skate but probably a carriage skate rather than a loco skate

Followed by good old springy wire

As long as the insulated wheels are earthed properly, usually by leaving the 2 rail pick ups in place but connecting then to earth all the conversions run well. The original HD pick ups and the Marklin skid will have a much longer life than any of the bent wire types as the copper they are made of will wear out with running.

Note that all conversions of plastic bodied locos, the Graham Farish one is diecast, result in the three rail pick-up slightly raising the driving wheels leading to inferior traction. If it is possible add weight to improve pulling power but in general a plastic bodied converted engine will not pull more than 2 HD coaches unless you are very lucky. However many of these tank engines run on branch lines and 2 coaches were a normal load.

I have more pictures but they all revolve around the same type of pick-ups.

All of my Wrenn conversions use normal HD pick-ups as they originated from HD and therefore genuine pick-ups will fit easily.

Please add a comment if you want more information but please note that all of my conversions have been bought in, I have not done any conversions myself.


13 Responses to 3 Rail Conversions

  1. nick baxter says:

    do you you of anyone who can do a 2 rail to 3 rail conversion????
    I would like my H?T Blue pullman to run on my HD 3 rail layout.

    Many Thanks


  2. Peter says:

    Very interesting site.
    Simple question:
    I have a 4-6-0 LNER Footballer 2 rail 12V DC Locomotive (inherited).
    Can I convert this to run on Märklin 3 rail track?
    My digital System Permits DCC/MM potocols. Thx. for any tips.

    • admin says:


      I presume that your Marklin 3 rail track is running 3 rail Marklin Engines with a Marklin controller operating them at 14 V AC. If this is the case then the 12 V DC engine will not run even if converted to 3 rail.


      Your Marklin track will operate with a 12V DC controller and then you can run the converted DC Loco. For converting the loco add a Middle pick up a Marklin skate will be ideal and route to the motor. Route the two rail pickups to earth. I have a set up with a Marklin controller and a HD controller attached to each of my running lines. Works with very little problems (sometimes the Marklin reverser mode is dodgy). I will post a picture in News.

  3. Garry Hall says:

    Hi, here is a link to one of my R1 3-rail conversions showing an un-weighted one pulling 4 coaches. There is a more detailed description on You Tube.


    Kind regards

    • tony says:

      Good effort on your part. I need two R1’s with plastic bodies to pull four coaches. An R1 with a diecast body has no problems with 4 up.

  4. David Murray says:

    Nice to see a prototypical goods train too. (H-D 3 rail on Wrenn track)

  5. Trevor Green says:

    What is the width of HornbyDublo track.? I’m wanting to ballast all my rails and want to put masking tape over the rails before I start. I now find I can buy different widths of masking tape.

  6. Peter Davies says:

    Interesting. I am in the process of running, Rovex, Triang, Hornby (Triang) Hornby Doublo 3 rail on the same track. So far I have used both the TTR Bakelite and fibre track with a three way switch to swap the current from two to three rail as and when required. Points are an issue. Taking the Bakelite point I have added extended check rails and glued them inside the existing check rail, this works after a fashion and keeps all makes on the track BUT derailments do occur due to the excessive depth of the gap next to the frog. I have laid a thin slice of plastic card on the track base but this is only partly successful. I have achieved through running both ways on the straight rail of the point but only some success on the curve, reasonably successful with SWB locos when trailing through the point but when facing the curve is very sharp and derailments are the norm.
    Bakelite track makes a really good clickerdy – click sound and is robust but the curves are a bit tight for Pacific’s. Fibre track has a slightly larger radius and really need pinning down, converter rails between the types of track are available.

  7. David Murray says:

    Peter, the derailments on curves can sometimes be that in the curve, the gauge narrows. I had this problem with a couple of diesels, Co-Bo and Bo-Bo after curving some old Wrenn 3 rail track. The solution that I found worked was to file the inside of the inner rail, thus widening the gauge. Also, the radius of the curve is sensitive. I need to make a new curve to a larger radius on another section where I sometimes get problems with carriage bogies slipping off. The golden rule is: wider the better!

  8. William says:

    Very interesting article on conversions. I have a decent amount of Hornby Dublo 3 rail,
    however I really like the diesel warships and want to try to convert one to 3 rail.
    Trix do one, along with Mainline, Hornby and Lima. My question is simply this, can anyone talk me through this conversion and will I be able to use a Dublo 3 rail pick up on anyone of the makes I have mentioned.


    • tony says:

      My most recent loco acquisition was a Trix 3 rail Warship, which I mention here Please note that the Trix scale is smaller that OO but larger than HO which is noticeable and that most Trix Warships were 2 rail. My one is still not a good runner unless it is going in reverse and on the uptrack, I think I know what the problem is but it’s not sorted yet. But Trix is authentic to the HD timeframe and is diecast and good and heavy. Despite its running problems it fits in very well with the rest of the fleet. There is one on ebay right now but you will have to question the seller as the description has nothing to do with a Warship but it does look like a 3 rail example. I must admit that I am getting into Trix as a way of getting new locos and rolling stock on my layout.

      Alternatively go for a cheap engine to convert. You can buy a Lima Warship for under £40 and at that price it is worth considering it as a guinea pig to learn how to do conversions. I have to admit I do not do many conversions as most of mine were bought already converted. However if you decide to go down this route I will advise you on what needs to be done.

      • William says:

        Dear Tony
        Many thanks for responding regarding the 3 rail conversion .
        This whole conversion business is like a black art to me, then again I guess you could say I need someone to show me the
        Step by Step how to do it.
        For example: the easiest cheaper option would be a Lima Warship.
        Can I use a Hornby Dublo 3 rail pick up somewhere underneath ?
        Can you talk me through the wiring?
        Do I need to add weight for traction?
        I guess fitting Hornby Dublo couplings is the easiest of the tasks.

  9. David Usher says:

    The simplest conversions are a small piece of metal bent down to touch the centre rail. Those brass headed paper fasteners work well, best to use in pairs. Plastic card, sugru and the ability to solder.
    Wiring is, or should be straight forward. There are two wires from the two track pick ups connected to the motor. Disconnect one and attach it to the other so that both track pick ups go to one motor connection only. A wire from the now empty motor connection needs to go to the centre pick up.
    Extra weight will probably be required to overcome the spring effect of the pick up. Commercial pick ups have light spring which is difficult to replicate DIY.
    Try and get the actual pick up under the outer axles on bodies or chassis where it will be centred better.
    Hope this helps. Unfortunately my ‘free’ website with pictures went belly up. Working on a new one.

Leave a Reply

Your email address will not be published. Required fields are marked *