"Jamie" wrote in message ...

And let us not forget that these non-pm alternators have not used brushes
for the field for years now. Nothing but bearings and the unexpected
mishap to take place now.

According to one reference, some models of wheel hub generators had problems
with water entering the enclosure when the bike was moved from a warm garage
to the cold outdoors and ridden in the rain. The temperature differential
created a relative vacuum in the hub which sucked water in through the seals
which were not designed with that in mind. Newer models apparently corrected
the problem. But if water does enter the assembly it tends to corrode the
rotor and stator poles which have very small clearance and cause them to
bind.

Paul