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From: "Ed Anderson" <eanderson@carolina.rr.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
References: <list-1156026@logan.com>
Subject: Re: [FlyRotary] Re: Oil Cooling Issues
Date: Thu, 15 Jun 2006 19:31:35 -0400
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Hi Joe,

Sorry to hear about your oil cooling problem, but if its any consolation 
your problem is not a new one {:>).

If you oil cooler is cool on the end furthest from the oil inlet/outlet 
thermostat then it clearly is not getting hot oil.  As several have already 
suggested your oil thermostat must indeed be open and diverting the oil from 
the core where it would be cooled.  I have not tried plugging the thermostat 
hole, so can offer no suggestions - besides, I would hesitate to remove the 
thermostat.  One of its functions is to have oil bypass the core when the 
oil is cold so that it can warm up quicker, but perhaps more important it 
can also provide a pressure relief function when the ambient air is very 
cold and preventing the excessive pressure of cold "thick" oil from building 
up in the oil cooler core.

Regarding your other approaches to solving your cooling.

One of the most important things I have learned about cooling is that it is 
very, very important that you do not have turbulent eddies near the entrance 
of your cooling duct.  Such eddies in effect cast an ever expanding "shadow" 
down stream over the cooling core reducing the effectiveness of the section 
of core "covered" by the shadow of turbulent air.   These eddies are 
primarily a result of a detached boundary layer of air next to the walls of 
the duct.  So expanding your inlet will not necessarily result in more 
effective  cooling if your inlet has eddies forming near the entrance - in 
effect you simply have more of your core frontal surface under the eddies 
shadow.

From my reading, it appears that the most effective duct (that I am aware 
of) is the streamline duct. Basically there is little expansion 
(enlargement) of the duct cross section until just before the core.  The 
streamline duct profile looks like a trumpet with the bell end against the 
core.  This approach keeps the air velocity high in the duct (reducing 
boundary layer separation) until the last moment where the duct is rapidly 
expanded into the trumpet bell just before the core.  While separation will 
occur there, any eddy formed along the wall  is so close to the core that 
its "shadow" is smallest and therefore more of the  core is exposed to 
effective cooling air flow.

Second, its important to have your core exit area at least 10-12" from any 
flow obstacle.  Obviously, these are idea conditions and can rarely be met 
within the constrains of our aircraft space.  But, the idea is to adhere as 
closely as you can to them.

It took me five modifications before I finally found success in reducing my 
oil cooler temperature.  But, once the oil temp problem was solved then the 
coolant temps fell into place

Good luck and keep at it

Ed

Ed Anderson
Rv-6A N494BW Rotary Powered
Matthews, NC
eanderson@carolina.rr.com
----- Original Message ----- 
From: "Joe Hull" <joeh@pilgrimtech.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Thursday, June 15, 2006 6:06 PM
Subject: [FlyRotary] Re: Oil Cooling Issues


> I used Pacific Oil Cooler Service to overhaul/clean/inspect my Mazda oil
> cooler and they did a great job.  If you tell them it is an automobile
> oil cooler and not an aircraft oil cooler, they will charge a lot less.
> I paid $112 in 2001.
>
> Here is a link to their website.
> http://www.oilcoolers.com/overhaul_service.htm

That link is a keeper!  THANX!

Joe Hull
Cozy Mk-IV #991 (In Phase1 Flight Test - 29.1 hrs flown)
Redmond (Seattle), Washington


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