Sender: <marv@lancaironline.net> (Marvin Kaye)
To: flyrotary@lancaironline.net
Date: Thu, 04 Mar 2004 19:26:17 -0500
Message-ID: <redirect-3063844@logan.com>
From: Mark Steitle <msteitle@mail.utexas.edu>
Subject: Re: [FlyRotary] Re: Ideal Cooling System Plumbing -- PLUS 
  'best coolant leak indicator'
In-Reply-To: <list-3063518@logan.com>
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David,
In my last response I failed to answer your last question.  Yes, the purge
tank will be as high on the firewall as I can get it.  This will be about 1"
above the top of the wp housing (I removed the thermostats and thermostat
housing to make clearance for the cowl)  I have found that is enough to
prevent draining coolant from the engine when I open the pressure cap.

I also have a plastic recovery bottle nearby, but lower than the purge 
tank.  It
is there to catch any overflow that would otherwise end up on the ground, and
allow the system to draw it back into the cooling system when the engine
cools.  IIRC, Tracy recommends this bottle be at least 1/2 gallon in size.  I
used a windshield washer bottle I had on hand.  The plastic tank has proven to
handle boiling hot coolant with no problem.

Mark


At 02:04 PM 3/4/2004 -0600, you wrote:
>Mark, thanks a lot for the photo and explanation.  Fills out my
>understanding a lot more.
>
>I think we've resolved the ambiguities of my original input.  I agree with
>all you said in this response.
>     -  Air trap in the thermostat bypass area seems to be a real "gotcha" if
>not carefully handled.  Frying an engine on initial startup has to be a real
>bummer.
>
>I'm glad you are going to monitor coolant level in the expansion tank.  I
>may not have been paying attention so I'll ask:  Are you using a "custom"
>expansion tank or one from an auto?  If homemade, will you scrounge a
>"level" sensor from a car's expansion tank?  Any particular one?  Already
>done it?
>
>Will your expansion tank be "highest possible"?  Or "anywhere" relative to
>top of engine?
>
>David
>
>----- Original Message -----
>From: "Mark Steitle" <msteitle@mail.utexas.edu>
>To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
>Sent: Thursday, March 04, 2004 1:19 PM
>Subject: [FlyRotary] Re: Ideal Cooling System Plumbing -- PLUS 'best coolant
>leak indicator'
>
>
> > David,
> > Somewhere I got the impression that your radiator returns were on the top
> > of the radiators.  Bottom
> > should be fine.
> >
> > I'll embed a couple of comments (and a wp flow diagram) to your comments.
>;-)
> >
> > Mark
> >
> > >The system I propose draws COOLANT off of the BOTTOM.  The AIR goes out
>the
> > >top, at least when you are filling the system on the ground with no flow.
> > >The main purpose is to be able to FILL the system and PURGE ALL AIR -
>right
> > >out the top of the engine - the highest spot you can find.
> >
> > Be alert to the possibility of air being trapped in the bypass circuit of
> > the wp housing.
> > Since I had removed the dual thermostats and welded up the bypass holes, I
> > had to remove
> > the hex plug (unique to the 20B) on the side of the wp housing to get the
> > pump to
> > prime.  Not sure how you would accomplish this on the 13B.  Maybe
>drill/tap
> > a 1/8npt
> > in the bypass area of the wp housing?  If you kept the thermostat, just
> > remove it while
> > filling the system.
> >
> >   HOWEVER, if plain old EXPERIENCE were to ever
> > >indicate that air was being trapped in the top of rad, then an AIR VENT
>LINE
> > >could be installed at high point in rad or a hose there that would feed
>back
> > >into the bottom (below liquid level) in pressurized expansion tank
> >
> > This is what I have been recommending.  But I plumbed mine to the side
> > fitting of the exp.
> > tank, still below liquid level.
> >
> > >- would
> > >be a "2ND AIR VENT LINE", with same function as the air vent line from
> > >highest point in engine block back to the expansion tank, below liq
>level.
> > >Both lines would be flowing a small amt of coolant that would be
>bypassing
> > >the rad, not being cooled, so, again, the caution to use SMALL AIR BLEED
> > >LINES or RESTRICTOR in the lines.
> >
> > A line from the top of the engine shouldn't hurt anything, except that the
> > coolant won't
> > be cooled.  As you mention, this is not an issue if the line is kept
> > small.  However,
> > if you have a method to bleed the air at time of filling, then I don't see
> > where this line is
> > needed.  Any air will be caught in the flow and eventually be separated
> > through the
> > radiator air-bleeder.  But, I don't see where it would hurt anything,
> > unless it were to
> > break in flight.
> >
> > >Air in the system:  We have hoses at the water pump inlet and outlet, and
> > >the pump is high up on the engine in a "plugs normal installation".
> > >     -  Where does the hose from the pump outlet feed back into the
>engine
> > >block - high or low on engine? (Basic question that I can't visualize
> > >because I don't have an engine yet)?
> >
> > The wp outlet connects to the top of the front side housing.  There are
>two
> > holes on
> > that housing where the coolant enters and exits the engine.  From the
>exit,
> > it goes
> > through the wp housing passages and up through the thermostat and out to
> > the radiator(s).
> > (Ref. attachment)
> >
> > >     -  Likewise, where is the "hot coolant outlet" from the engine block
> > >where the hose connects to the radiator?  Should be high up near the top
> > >like on all cars?
> >
> > Yes.
> >
> >
> > >Anyway, the assumed short hose from pump outlet to somewhere on engine
>could
> > >have a leak;
> >
> > There is no hose here, only a gasket.  (see attachment)
> >
> > >  likewise, the hot coolant hose that runs DOWN from near the top
> > >of block to the rads could have a leak anywhere below that outlet from
>block
> > >all the way down to connections to the radiators.
> > >     - As long as there is a head of coolant in the engine, there is
>going to
> > >be a head of coolant down at the rads, and so the pump is going to have
> > >coolant at the bottom of rads to suck UP to the pump.
> >
> > Yes, provided we're drawing off the bottom of the radiator and not the
>top.
> >
> > >     - I don't envision any significant pump-stopping air at the bottom
>where
> > >pump is sucking from as long as there is any coolant in the block.
> > >  The
> > >pump is going to suck from bottom of rads and pump out of its outlet into
> > >the engine block and/or out the "leak" until there is ZERO coolant left
>in
> > >the rads, at which time the pump stops ciruclating - but not because of
> > >"system configuration", rather for lack of liquid.
> >
> >
> > This is where the rotary is different than other engines.  It can get an
> > air-lock in
> > the coolant bypass circuit.  Normally happens when first filling, or
> > re-filling the
> > cooling system.  By the time the thermostat opens, you've damaged the
>engine.
> > Once you've "primed" the system, this is probably not going to
> > happen.  Although
> > a coolant shortage could cause the pump to loose its prime.
> >
> >
> > >     -  Again, I simply assume any AIR THAT IS BEING SUCKED IN AT THE
>LEAK
> > >will be up ON TOP of the coolant, not down at the bottom of the liquid
> > >column where the pump sucks from.
> >
> > I think that the air could accumulate anywhere there is insufficient flow
> > to move it
> > along to somewhere else.
> >
> >
> >
> > >Now, to address the discussion of "What is the best indication of a
>leak?"
> > >
> > >     -  THIS IS THE BEST SYSTEM:  It tells you coolant level in EXPANSION
> > >TANK has decreased too much, BEFORE the level in the BLOCK has even begun
>to
> > >suck air.   This is the ideal warning - warned BEFORE the engine is
>damaged,
> > >gives "more" time (depending on speed of leak) to take action to land and
> > >save the engine, if that is possible, given where you are and where the
> > >closest landing spot is.
> >
> > I plan on monitoring Coolant Level (sensor in exp. tank), Coolant
>Pressure,
> > and
> > Coolant Temp using Tracy's EM-2.
> >
> > Mark S.
> >
>
>
> >
>
>
>
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