Sender: <marv@lancaironline.net> (Marvin Kaye)
To: flyrotary@lancaironline.net
Date: Thu, 04 Mar 2004 19:26:17 -0500
Message-ID: <redirect-3063853@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>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"; format=flowed

David,
I'm using p/n 2584 as shown at http://www.pegasusautoracing.com/pdfs/065.pdf
While they refer to it as an expansion tank, I believe the correct term is 
purge
tank.

My level sensor came from McMaster Carr.  They have quite a selection, but
only a few that can handle the heat we're asking, and are reasonably priced.
Search on "liquid level sensors".  The one I selected was about $28.  It 
worked
fine, except I had to replace the flimsy washer for a better one.  I plan 
to wire
it up to my annunciator panel.

Mark S.


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.
> >
>
>
> >
>
>
>
> >>  Homepage:  http://www.flyrotary.com/
> >>  Archive:   http://lancaironline.net/lists/flyrotary/List.html