OK, back to "How's It Done?" ... the next topic is:-Metadynes!
(and why not?)
I remember these from my youth. Not misspent, but rather well
spent in places like Arborfield, and (later) in various tank parks and such like.
For those who have yet to hear of them, the metadyne was a "rotating amplifier", or "cross-field generator" with (IIRC) a shorted link at 90° or so to the main commutator brushes. They were used to control (for example) big guns in tanks and such like, and, I believe, as part of the traction control system in certain electric locomotives.
It was heavy duty stuff, and they really "sang" (or should that be "groaned"?) when the gun turret (etc.
) was slewed
. Externally, and to the lay person, they looked like "double-ended motors". But only one end was the driving motor, the other being the "cross-field generator". The output - DC, of course - (which could be zero to Big Amps in a matter of milliseconds) went off to the turret motor (etc.
Kit like this could take a bit of stick (abuse, in other words) ... from hard-left to hard-right, and all the rest. But I don't remember one failing. Which was just as well, as I seem to recall that they weren't especially easy to get at (on the Chieftain tank at least). But do I also remember correctly that they were on the floor of the turret, under the gun, on the Centurion?
I hear that metadynes have been superseded by solid-state control systems these days. Can this be true (has anyone got a circuit diagram - big SCR's and such, I suppose) ... and, why?