wrote in message
...
On Thu, 30 Apr 2009 10:59:29 -0500, Richard Casady
wrote:

On Thu, 30 Apr 2009 12:48:01 +0200, "Steve Lusardi"
wrote:


US Five cent coins are 75% nickel and 25% copper. This is close to
monel.
Probably why they make such great washers !
Copper washed zinc pennies (about the only ones you see these days)
are pretty good too.



Reminds me of an experience I had with my father-in-law on his boat many
years ago.
He had an old Uniflite equipped with trim tabs. The control for the trim
tabs was a joystick type switch that applied power to the hydraulic motor
and valves to the tabs. Power was applied in the switch through a set of
contacts and a copper washer.

He had been having problems with the system, taken the switch apart and
decided to replace the copper washer because it was pitted from making and
breaking the electrical contacts over many years of use. He had just
finished re-installing the switch when I arrived at the dock and he asked me
to stay on the dock and watch the trim tabs to make sure they moved as he
manipulated the joy switch. All was fine until I happened to look up at
him in the cabin of the boat. He was facing me, manipulating the switch
behind him, and smoke was pouring out of the enclosure that contained his
instruments and the joy switch.

Turns out he had used a stainless washer to replace the copper one. The
current draw through the switch was over 10 amps. Stainless is a poor
electrical conductor and the replacement washer in the switch was glowing
red when we pulled it out of the console and tried it again so we could see
it.

So, with no copper washer available, he drilled a hole in a penny and tried
that. Worked fine.

Eisboch