"Fred Abse" wrote in message
news
On Thu, 01 Dec 2011 17:28:41 -0700, Jim Thompson wrote:

Once I looked up a Sturmey Archer "dynamo"

In 1936 terms, the multipole ring magnet in those things was quite cutting
edge technology. They must have used an ingenious magnetizing machine.

How did posts from my thread get in the OVP thread?

Not to worry though - apparently the 20 pole magnet ring is either cast or
sintered from the type of alnico that depolarises instantly if you remove
the keeper, apparently if you take out the armature for mere seconds the
dynamo is scrap, its also stated that the alnico slowly but surely loses
magnetism over time even if not interfered with.

It crossed my mind to dump a high voltage capacitor into the armature
winding (making sure the poles are aligned) but I don't have a surplus of
armatures to risk destroying the windings.