User-Agent: Microsoft-Outlook-Express-Macintosh-Edition/5.02.2022
Date: Tue, 15 May 2001 11:02:26 -0700
Subject: RE:  Altitude switches
From: Hal Woodruff <woodruff@swefco.com>
To: <lancair.list@olsusa.com>
Message-ID: <B726BD42.2390%woodruff@swefco.com>
In-Reply-To: <20010515044034.AAA1678@pop3.olsusa.com>
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Reply-To: lancair.list@olsusa.com

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I'll really be ordering the altitude switches on Fri 5/18/01.  (My last post
to the maillist didn't get in yesterdays collection.)

There's been some confusion over the purpose of the reservoir.  Here's an
explanation of how it works.

The reservoir is a small trapped volume of air at, hopefully, standard
conditions of sea level pressure (29.92 inches), temperature etc.  The
switch is a pressure switch as opposed to a vacuum switch.  When you ascend,
the surrounding air pressure decreases allowing the trapped air in the
reservoir to apply pressure to the bellows in the switch.  When you reach
approx. 10,000 feet the pressure from the reservoir (sea level pressure)
will exert enough pressure to activate the switch.

You'll need some type of sea level reference - either the one I can provide
or your own construction.

In the picture, the reservoir is the brass fitting on down.  (I plan on
trying to find a light weight alternative for the brass fitting).

I'm putting two of these in my plane.  One will be mounted in the gear box
area (unpressurized) to run a warning light to remind me to turn on/off the
fuel pump low boost.  The other will be mounted in the cabin to run a light
to warn of cabin pressure less than 10 psi denoting pressurization problems
or as a reminder to turn on the pressurization.

I'll include with the switch an electrical drawing that shows how I'll be
wiring the switches.

Hope that this helps,

Hal

> If you want a switch(es) and you did not receive an email from me dated
5/14/01 then I missed your request.  Please email me at woodruff@swefco.com
with your request and I'll get you in on the purchase.

>Price for the switch alone is $30.00 ea.  If you also want the reservoir
>then include an additional $5.00 ea.

>I'll email back to with info on where to send your check as a confirmation that
I got your order.


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LML website:   http://www.olsusa.com/Users/Mkaye/maillist.html
LML Builders' Bookstore:   http://www.buildersbooks.com/lancair

Please send your photos and drawings to marvkaye@olsusa.com.
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