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Date: Mon, 27 Jun 2005 00:02:03 -0500
From: Jim Sower <canarder@frontiernet.net>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: Coolant Leak
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I think the pressure transients CAN'T be a good thing, or even benign. 
Maybe they're not big enough to fail something (like a radiator tank, or 
a flue or something YET, but will eventually. In any event, they dirty 
up your data just like Al says, and it's so easy to make that transient 
go away (Al"s cup of air) that I can't see any rational reason not to 
take that anomaly off the table and get back to reliable, smooth 
tracking pressure so as to simplify interpretation of the coolant 
pressure reading.

Definitely with Al on this one ... Jim S.

Al Gietzen wrote:

> I agree, Al. I don't see how that much heating of the coolant could 
> happen in a second or two. I personally think it has to do with lack 
> of any air in the system as it does not do that when there is air 
> present. Could the fact that I used stainless steel braided lines for 
> the coolant system minimize expansion? In any case, I have flow with 
> that condition for several hundred hours with no apparent ill effect, 
> so it does not appear to be anything detrimental to the operation of 
> the engine.
>
> Ed
>
> The important thing is that; whatever the cause, the pressure 
> transient is apparently a non-issue. Certainly lines covered with 
> braided SS aren’t going to expand much, but they still have flexible 
> walls in there that do distort bit with pressure, as will the 
> thin-walled tank on a radiator. Clearly there is a hydraulic pressure 
> being transmitted through the cooling system. My guess is that the 
> cause is likely the immediate expansion of the inside walls of the 
> rotor housing (temperature and pressure) while everything else is 
> cool, followed closely thereafter by initial heating of the coolant. 
> Heat transfer through the rotor housing does not happen 
> instantaneously. It’s a guess, but hey; other than for mental 
> gymnastics, who cares?
>
> Al
>