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Three-Rail Track

Melvin has a quick question:

“I saw a video with 3 rail track and query why the need for 3 rails when two would do? Just curious.”

10 Responses to Three-Rail Track

  • Ward Gaineysays:

    3 rail was used in early Hornby and Marklin where the two rails provide one source of power (negative) and a continuous row of ‘studs’ in the middle of the track provided the positive source with the power pickup ‘skid’ in the centre of the locomotive. Some vintage train specialist run these and there is a suggestion there is better connectivity with two rails and the centre stud-3 contact points as opposed to two.
    A bit tricky around points with the centre pick up.

    • SteveBsays:

      Lionel also uses a 3-rail design and uses double spring loaded rollers to pick up the power from the center rail. The Lionel trains were considered toy trains and were designed with children in mind. Lionel considered the 3-rail design easier for an 8 year old to place engines on the track. The original Lionel trains were made in “0” and “027” gauges which are significantly larger than the “H0” gauge.

  • Melvinsays:

    that explains a lot. thanks Ward.

  • Kimsays:

    I feel it is unrealistic, HO scale systems work great look like real trains

  • Ian McIntoshsays:

    3 rail track has a couple advantages:
    – It means wheels and axles do not need to be insulated, since both outer rails a electrically connected anyway. With 2 rail, at least one wheel on every axle must be insulated. That mattered more in the early days when wheels were metal, less now when they are often plastic.
    – It means reversing loops, wyes and turntables do not need extra insulating and special wiring. With 2 rails, going around the loop means the left rail ends up the right and the right the left – an instant short circuit. With 3 rail there’s no problem. With 2 rail using DCC you can buy a circuit to detect the short circuit and instantly reverse the power to the loop (with DCC doing that doesn’t reverse the train direction), but you have to do extra insulation, buy the circuit and wire it up.

    BTW, some old layouts were built with “outside 3rd rail”, and that’s even prototypical for many or most subways. It was more a “do it yourself” solution but back then most serious model railroaders built their own track and switches.

    Of course 2 rail looks much more realistic for most prototypes, and the track is a little cheaper from using one less rail..

  • SteveBsays:

    American Flyer trains were also larger “toy” trains, but they were a 2-rail design. I don’t know what their solution is for something like a reversing loop on a child’s layout. I had one friend who had American Flyer but his was an oval.

  • André du Toitsays:

    My comment could be way out of line, but keep in mind that the above comments all relate to model railroading. A three rail system is also used in the real world. This is to accommodate two different rail gauges and not for supplying power to the locomotives. There could be several considerations for such a practice, one of them being that land for two different rail gauges in parallel is not available. This arrangement leads to very interesting and innovative points and crossings solutions. There are a few videos on cab rides where one can see the view of the driver in such situations. A good example is the line from Chur to Filisur in Switzerland.

    • Anselmo Agostinhosays:

      That´s a clever observation. Let me add that in the model world we also have the HOn3 dual gauge three rail version, in which we can run HO and HOn3 trains. Micro engineering (USA) sells them.

    • John Byerssays:

      Another example of dual gauge on real railroads was the D&RGW in Colorado. 3 foot narrow gauge and 4′ 8.5 inch standard gauge. Of course the inner rail was not in the center, since 3′ is more than 1/2 of 4′ 8.5 inches.

      Ian of course was right about the reversing loop being one of the main advantages of 3 rail track when used on a “toy” train set. When I was 5 or 6 & got my first Lionel train set I wasn’t worried about the unrealistic 3rd rail, I was just happy to have an electric train. I became more concerned with realism as a teenager and switched to HO 2 rail.

  • David Smithsays:

    The Marklin centre stud system improves the look over having a centre rail.

    I am surprised that nobody mentioned TRIX TWIN used a three rail system to be able to run two trains independently on the same loop of track. Correct me if I am wrong, but they came with a double controller with two separate 12V windings on the transformer and one was wired left rail to centre and the other was right rail to centre. I guess that they had a switch under the loco to select which controller they were connected to.

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