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Date: Tue, 04 Sep 2012 23:16:46 -0400
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From: Robert R Pastusek <rpastusek@htii.com>
Subject: RE: [LML] Re: Temp effect on hydraulics
Thread-Topic: [LML] Re: Temp effect on hydraulics
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Ed,
The problem is not trapped air; in fact, it's the lack of air that is the p=
roblem. In a closed system like the 2-seat Lancairs, the hydraulic fluid is=
 trapped in a closed system. It has a low coefficient of expansion, but it =
does expand when heated. With no place to expand, the pressure spikes. The =
4-series Lancairs have an accumulator (basically a bottle with a rubber mem=
brane inside that separates compressed air on one side and hydraulic fluid =
on the other). This allows the heated fluid a place to expand...and compres=
s the air in the accumulator just a bit; the pressure rise is probably not =
even noticeable. When you first service the system on a 2-seater, there is =
always a small amount of trapped air. Over time, this gets flushed out of t=
he system, and the ability to absorb even a small expansion of the fluid di=
minishes...hence the pressure buildup.

Hope this helps.

Bob

-----Original Message-----
From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of Ed G=
ray
Sent: Tuesday, September 04, 2012 4:19 PM
To: lml@lancaironline.net
Subject: [LML] Re: Temp effect on hydraulics

What is the coefficient of heat expansion on hydraulic fluid?  Seems that b=
ig pressure changes would be caused by trapped air.  Auto brakes don't fail=
 in low or high temps.  Could it be trapped air in the fluid line to the se=
nsor?
Ed Gray L360 Nearly complete with test hours, Dallas

-----Original Message-----
From: Lancair Mailing List [mailto:lml@lancaironline.net]
Sent: Tuesday, September 04, 2012 5:01 AM
Subject: lml Digest #3893

        Lancair Mailing List Digest #3893

 1) Re: Critical Service Bulletin
    by Silvio Novelli <ppxsn@novellisouza.com.br>
 2) Barrett at fly-in
    by "Claudette Colwell" <colwell.ch@gmail.com>
 3) Re: Critical Service Bulletin on Cruise RPM
    by Silvio Novelli <ppxsn@novellisouza.com.br>
 4) Re: Critical Service Bulletin on Cruise RPM
    by Colyn Case <colyncase@earthlink.net>
 5) Re: Thermal influence on Hydraulic Pressure
    by "Danny" <danny@n107sd.com>
 6) Re: Thermal influence on Hydraulic Pressure
    by Frederick Moreno <frederickmoreno@bigpond.com>

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