Hornby Double 3 rail and DCC

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I hope that this is appropriate to ask. I am about to build a Hornby Doublo 3 rail layout with 50 year old kit (!) - often available on eBay. The engines use permanent magnet DC motors with only three sets of coils on the armature, current is picked up from the wheels (metal axles) and a central pick-up.

It is probably a lot to ask but the idea of DCC is very appealing and, if possible should be considered beofre track laying and design commences. Does anybody have any thoughts, suggestions or experience of such a conversion please?


-- Garry Nevin (small@freezone.co.uk), March 13, 2003



DCC sounds like a good fit. The only thing you need to consider is how much current the loco motors draw and be sure to choose a decoder that can handle that amount of current. There are numerous references to how to determine the stall current of a motor. If it is too high for decoders that are designed for HO, then you may have to choose a decoder designed for O scale. This might lead to a problem of finding space to install the decoder.

But if you can solve the space problem, then you shouldn't have any real problems using DCC.


-- Dale Gloer (dale.gloer@sympatico.ca), March 14, 2003.


Apart from the current-related issues...

As per various postings, e.g. Brass Locos, DCC require that BOTH motor brushes be insulated from the track.

Also see: http://www.mackaymodels.co.uk/Decoder%20Fitting%20Hints.htm

The traditional Hornby-Dublo motor (as in 0-6-2T, 2-6-4T, A4 4-6-2 and Duchess/City 4-6-2) has one insulated motor brush connected to the centre-third-rail collector (easy to divert the wiring) BUT the other motor brush is earthed/grounded to the chassic block - compare with insulated bush. You'll have to extract the uninsulated brush assembly, probably enlarge the hole, then refit the brush assembly plus extra insulation - with the correct brush pressure! The trouble with buying second-hand HD is that you have no idea of the wear on the brushes or state of the brush spring. THe raelly big gotcha is that those old magnets weaken..... more current, more heat, less traction! The other locos have either a traditional "long" DC motor with conventional "arm" brushes or the ring-field motor, both of which ought to be easier to double insulate. Again, brush wear and de- magnetisation are common gotchas. These matters can be fixed, at a price!

Any Hornby-Dublo that's in reasonably good condition is probably worth more today as a collector's item than as a basis for a working model railway. As soon as you tamper (eg fit DCC) to a collector's item, you've "ruined" and devalued it. You could ask the Hornby Railway Collectors Association http://www.hrca.net/ about that.

If you really fancy the nostalgia of having Hornby-Dublo you ought to be prepared to love the traditional control system that is of its era! After all, all you need to do on HD 3R to insulate a section is to put an insulating tab (or even a piece of cardboard) between any two track pieces. If you don't have terminal rails you can always tuck a wire into the connector to feed the section. None of your nasty insulated fishplates with HD 3R :-)


Rodney Hills Surrey, England

-- Rodney Hills (rodney_hills@hp.com), July 16, 2003.

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