Tell me if I’m remembering this stuff wrong.
I think the charge warning (“Ign.”) lamp on a dynamo-equipped car served the “nudging” purpose described above, by feeding a small current to D, which was connected to F when the regulator contacts were in the no-charge position.
Reckon that's about it TT.
A quick look at any old car wiring diagram, eg Morris Minor or whatever, shows the lay-out of a typical charge-warning light (A via fusebox to Sw to bulb to D), which if we fitted a suitable switch we could replicate easily enough on dynamo bikes. Loads of dynamo machines with coil ignition had such as standard.
With F and D being always connected through closed regulator contacts except when the system is actually regulating, a feed to D will give the field a gentle nudge, just as a direct one to F via a resistor or bulb will, per the nudge diagram the Ariel folk created.
(Or of course we can give the whole system a good kicking and shut the cut-out momentarily on a mechanical control box if we can get the lid off easily, or by touching battery live to F, as many people do when pressed.)
Have sometimes thought about going for warning lights or those ''red, amber, green" things we see advertised (think Goff sells them), but heck, ammeters are good enough for me.
