REFLECTOR: Low CHTs

[Ron Brown]

Hi John,

I think that is a GREAT idea - using bimetallic springs.  I have been
thinking about adding butterfly valves in the NACA down ducts, but didn't
want to run actuating cables.  However, the bimetallics would be a great
approach.  Two thoughts, build the valves so that they can't close
completely off, i.e. they can only close part of the air flow off.  Second,
the airflow should try to open the valves, the bimetallic would close the
valve with cold OAT.  However, the bimetallic springs in carb chokes
operates off of either exhaust heat or an electric coil - I've seen both
used.

My cabin heat is working good down to about 30 degrees or so - as some one
suggested earlier, closing off the damper valve completely restricts the
amount of cooling of the oil, and therefore causes the engine to run warmer,
hence warmer oil and vernatherm opens.  (did that make any sense???)  But my
heads are running around 310 degrees which is a bit cool.

Ronnie


----- Original Message ----- 
From: "John Dibble" <aminetech at bluefrog.com>
To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
Sent: Wednesday, January 17, 2007 12:49 PM
Subject: REFLECTOR: Low CHTs


> This time of year my CHTs are low and my oil temp is also, making it 
> difficult to heat
> the cabin.  I'm thinking of putting butterfly valves in the engine cooling 
> inlets,
> similar to what is in my engine intake air for carbureator heat.  Rather 
> than run
> cables, I'm thinking of using a bi-metallic spring, like is used for 
> automatic chokes
> on cars to open and close the valves.  Ideally the spring would work off 
> of CHT, but I
> think this will be to complicated, so I think using OAT would be more 
> practical.
> Any thoughts whether this is a good idea?
>
> John
>
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