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Reply-To: "dfs" <dfs@gateway.net>
From: "dfs" <dfs@gateway.net>
To: "Lancair List" <lancair.list@olsusa.com>
Subject: Solenoid
Date: Fri, 19 Nov 1999 22:57:28 -0800
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To Bill Hogarty, re: a solenoid that will last for an hour whilw energized.

Bill, you've got one (or da-- well should have one) in your airplane right
now - it's called the "master relay" or some such. Cheap as a Big Mac and
far more reliable. Just be sure to use the one intended for the master relay
position. It's on all the time your master switch is on and is quite capable
of carrying a lot of current - might I point out that the garden variety
"master relay" happily carries the starter current (which can be a couple
hundred amperes) without too much problem.

Just be sure that you don't choose a "stater relay" which has a very low
coil resistance and shouldn't have power applied for more than a few seconds
at a time.

Another possible choice is the automotive high current relays. They look
like a small black cube (maybe 1 to 11/4 inches on a side) and are available
in ratings up to 70 amps at 12 volts DC. The relay manufacturers, Bosch and
Guardian and a couple others, make them and they are quite reliable. I've
used them in my airplane for over 500 hours and have yet to have a failure.
Granted, I'm not using them for starting motor loads but they are
double-break type relays and should fill the bill.

Dan Schaefer


[Dan... I think what Bill is looking for is a solenoid only, forget the
contacts part of the relay.  Seems to me he wants to use the movable solenoid
part of the relay as a mechanical actuator for his flap door.  Then again,
maybe I misunderstood his original post as well <G>.  I imagine one 
could take a master relay and cabbage the contacts end of it and turn it
into a pretty compact linear actuator.  I think the stroke would be way
too short, though, given the operating characteristics of a typical power
relay.  If I'm way off base here, never mind <g>.

   <Marv>         ]
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