Phil Allison wrote:

"John Stewart"
Phil Allison wrote:

** Beware - anodised aluminium is an INSULATOR !!!

Any areas to be used for grounding will need to be SCRAPED bare first -
a
real PITA.

One of the summer jobs I had while still in high school was running the
anodizing machine at DeHavilland Aircraft near Toronto. The drop off wing
fuel
tanks for the Vampire (DH110) jet fighter aircraft which first flew in
Sept of
1943 were all anodized in a large tank of Chromic Acid. The whole thing
was
powered by a motor /generator set up. When first turned on the DC current
to
the bath was very high but as time progressed the voltage had to be
increased
to maintain the current. Eventually the wing tank was finished & lifted
out for
rinsing in water, then dried. As Phil has noted, anodizing results in a
very
thick layer of high resistance on the surface of the Aluminum (Aluminium).


** That is one hell of a coincidence JS !!!!

One of my customers, here to pick up his EV 'Entertainer' yesterday, was
telling me how he worked at Hawker DeHavilland's facility at Bankstown in
Sydney - on Vampires !!!

The front fuselage was made of plywood and covered in fabric - which as a
lad he painted with many coats of silver paint to help make it look like
alloy !!

............... Phil

The nose of the aircraft contained a DF (Direction Finding radio) which was
considered a piece of super-mega-secret apparatus in the beginning. There was an
explosive charge in the nose that would destroy the radio should the aircraft
crash in enemy territory.

By the time we were working on these aircraft several radios had been destroyed
by a simple hard landing of the aircraft. Imagine how surprised the pilot was
when the nose of his aircraft would explode on landing. One of the jobs
specified in the maintenance contract at DeHavilland Canada was the removal of
this nasty little gadget.

The triggering device was a one inch diameter steel ball that would fly forward
when you hit the deck to hard. That closed the contacts & the charge would
explode.
The steel ball looked like a giant ball bearing.

These balls also looked like the balls in a pin-ball machine. I took some with
me to a local restaurant where the owner had a pin-ball set up to make money.
The owners son often played the pin-ball & would push it around the floor trying
to get the balls going where he wanted them. I waited a couple of minutes &
dropped a few of my steel balls on the floor under the pin-ball machine, then
told the kid he had busted his father's machine. He picked up the balls from the
floor & desperately tried to find a hole on the underside where he could fit
them back in, but no luck!!

Cheers, John Stewart