There are kits to rebuild Hornby ringfield motor drives that install a "CD Motor" in place of the original armature and field magnet. CD motors are cheap, but these kits are not when you figure in the cost of shipping from the UK.
It would be great to learn the specification of those motors. Does anybody have a spec and be willing to share it?
I don't know if there's much interest in Hornby Ringfield-motor conversions here.
For those interested in the subject:
Strathpeffer Junction kit video:
https://m.youtube.com/watch?v=FZ4arAaiNYs
Horns and Whistles tutorials:
Installation
https://m.youtube.com/watch?v=D3setAw7tM0
Wiring for DCC
https://m.youtube.com/watch?v=P19Zp5CSahQ
It might be mentioned that at least one modeler simply used a suitable-thickness cardboard tube as an 'adapter ring'...
The thing is, these are transverse 'pancake' motors, and almost nothing that is North American would use this drive by choice vs. a larger longitudinal motor with worm or tower drive. Accordingly I don't think you'll get much assessment of short large-diameter motors; there are obviously 'inexpensive manufacturers' of the motors if the Horns and Whistles guy complains about eBay sellers of rip-off discounted kits.
I have had no problem finding tutorials about installing these motors. And I see nothing challenging there.
What I am looking for is what motors are suitable for this job. There seem to be tons of CD motors on eBay that should fit. But their voltage ratings are 5, 5.9 or 6 volts. Maximum model railroad track power tends to be 17 volts. That's too high for comfort, even given the likely overdesign of the electrics.
Yeah there are kits you buy, with the motor and all the hardware. Pricey though. Not the kits themselves, but with shipping added - yikes! My guess is the motors cost US$3 to 5, purchased in quantity from Asian sources. It would be nice to find suitable motors without paying a heady markup.
I also note many caveats about the heat-intolerance of the 3D printed adapters in the manufacturers publications. Printing them in PLA -- one of the least heat-tolerant printing plastics -- I feel is a mistake. I would have printed them in PETG or TPU. Much better performance. TPU -- ThermoPlastic Urethane -- might also make fitment easier as it has more 'give'.
If I can find suitable motors I might be tempted to produce my own kits. I have the design and printing skills and equipment.
There are two places the nominal voltage of one of these motors will 'matter'. One is the breakdown voltage of the windings. The other is the motor reaching its top or rated rotational speed at the indicated voltage.
It was my understanding that the 'track' voltage was comparatively less important for DCC, as the only voltage the motor 'sees' will be what the decoder feeds it (usually as part of a complex waveform). In any event I'd look for a motor with a 14-15V rating. I'd expect you'll be seeing magic smoke sooner rather than later with a motor in the 6V range.
The point of listing those European suppliers is that they've obviously figured out where and how to source the appropriate motors. I have no idea whether they'd "helpfully" advise you of sources -- note the one maker complaining about large numbers of Asian-sourced ripoff kits, which wouldn't bode well for cold-call requests...