In various places in the description of the RSR new layout, there have been references to a 3rd rail that was to be laid along some of the track to allow Hornby Dublo, JEP and Märklin trains to be run but it was really for the sake of the JEP 232R. With the completion of the southern loops, it was time to start on the contrun2 section, which was the first stage of the layout project to incorprate a 3rd rail.
It was only after carrying out the first few experiments that it became clear just what was involved. There was certainly more to it than simply laying a third rail (or stud contact strip) down the centre of the track. Getting through the points turned out to be the stumbling block that brought about the fall. Of course, centre 3rd rail and stud contact are perfectly viable power supply concepts - just look at Märklin and Hornby Dublo. However, their solutions are an integral part of their track systems and were catered for - designed in, if you like - from the very beginning, whereas on the RSR, a large part of the the centre conductor was to be added to existing trackage that is already installed, fixed down, lined up and wired in, and includes numerous points and double slip crossings.
Another problem is the current collection. Stud contact was selected for the visible tracks for appearance's sake. The Märklin models, of course, already have their skates but the Hornby has "spoons" and the JEP plungers, neither of which can be used on stud contact. And this is before we even try to get the collectors across the intersecting running rails. With Hornby and Märklin, the affected part of the switch rail is electrically dead; in JEP points, the whole switch rail is made of plastic. With 3-rail, that doesn't matter but such no-go areas are no use where 2-rail trains are also meant to run. And although it's possible to modify 2-rail points with appropriate switching, you can really only do that before the tracks are laid. Tracks already in situ: forgeddit.
Fitting skates to 3-rail locos should, in theory, be no problem. I never got round to trying it out but I suspect the Hornby Dublo engines would be simple enough. The JEP 232R, however, is quite another kettle of fish. She has very little "ground clearance" under her chassis; the pickup plungers jut down in front of and behind a bottom casting that accommodates the motor. The spacing of her tender bogie axles precludes a long skate there as well. (It would have to a long skate to get across the switch rails of the points.) At one point (no pun intended) I even went to the length of buying a spare bottom casting (on eBay France) to make any modification reversible.
All in all, with all these stumbling blocks the 3rd rail project for the RSR was essentially a non-starter but in the final analysis it was the failure of the experiments with stud-contact points that its sealed fate. Maybe I gave up too early but the rest of the layout was also being held up. I would very much have liked to see the 232R running on the new layout but you can't have everything.
The work is also documented on flickr:
https://www.flickr.com/photos/53775591@ ... 1263176086
Cheers,
Artur