Today's Message Index:
----------------------
1. 12:40 AM - Re: TeamGrumman-List Digest: 3 Msgs - 09/06/04 (Tiger 67B)
2. 04:11 AM - Re: Air-Oil Separator (Mike Lehman)
3. 06:38 AM - Re: Air-Oil Separator (flyv35b)
Message 1
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| Subject: | Re: TeamGrumman-List Digest: 3 Msgs - 09/06/04 |
--> TeamGrumman-List message posted by: Tiger 67B <jnpsavage@cox.net>
The main problem people have with the M20 is that it HAS to have a
"downward" flow (no "flat spots in the little return line) or it won't
work... I've had one for about 2 yrs now and I'm convinced it would work
better if I had mounted it on the co-pilot's side instead, thereby
giving the return line MORE "down" ... right now, mounted on the pilot's
side, it has a big "flat spot" (where the line is horizontal) and this
is the reason it is not as effective as it might be...
It tells you in the instructions that it MUST HAVE 'DOWN' or it won't
work... it is gravity fed oil return.... and instructions say that is
the main problem if it isn't effective. I'm changing sides in a month at
annual.
Jan Savage
Tiger 67B
TeamGrumman-List Digest Server wrote:
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> TeamGrumman-List Digest Archive
> ---
> Total Messages Posted Mon 09/06/04: 3
>
>
> Today's Message Index:
> ----------------------
>
> 1. 05:33 PM - Air-Oil Separator (Dave)
> 2. 07:39 PM - Re: Air-Oil Separator (Gil Alexander)
> 3. 11:52 PM - Re: Air-Oil Separator (TeamGrumman@AOL.COM)
>
>
>
> ________________________________ Message 1 _____________________________________
>
>
> Time: 05:33:38 PM PST US
> From: "Dave" <ddmcknight@alltel.net>
> Subject: TeamGrumman-List: Air-Oil Separator
>
> --> TeamGrumman-List message posted by: "Dave" <ddmcknight@alltel.net>
>
> Looking for advice on air-oil separators for a Tiger. I keep the oil at 6 qts.
> but still get oil on the belly.
> Does the M-20 unit work as advertised??
>
> I appreciate any input anyone can offer.
>
> Dave McKnight
> Tiger N880DM
>
>
>
>
>
>
> ________________________________ Message 2 _____________________________________
>
>
> Time: 07:39:23 PM PST US
> From: Gil Alexander <gilalex@earthlink.net>
> Subject: Re: TeamGrumman-List: Air-Oil Separator
>
> --> TeamGrumman-List message posted by: Gil Alexander <gilalex@earthlink.net>
>
> Dave ... check how far your oil relief tube penetrates into the air stream.
>
> I think the desired number is 1.25 inches.
>
> Mine was more, and when I reduced the amount below the cowl to 1.25 inches
> the belly stayed cleaner...
>
> ...gil in Tucson
>
> At 05:33 PM 9/6/2004, you wrote:
>
>>--> TeamGrumman-List message posted by: "Dave" <ddmcknight@alltel.net>
>>
>>Looking for advice on air-oil separators for a Tiger. I keep the oil at 6
>>qts. but still get oil on the belly.
>>Does the M-20 unit work as advertised??
>>
>>I appreciate any input anyone can offer.
>>
>>Dave McKnight
>>Tiger N880DM
>>
>>
>
>
>
>
>
>
>
> ________________________________ Message 3 _____________________________________
>
>
> Time: 11:52:02 PM PST US
> From: TeamGrumman@AOL.COM
> Subject: Re: TeamGrumman-List: Air-Oil Separator
>
> --> TeamGrumman-List message posted by: TeamGrumman@aol.com
>
>
> In a message dated 9/6/04 5:34:32 PM, ddmcknight@alltel.net writes:
>
>
>
>>Does the M-20 unit work as advertised??
>>
>>
>
>
> My experience is taht the M-20 doesn't have the volume necessary to be of
> much help. That, and it doesn't have a positive flow back to the engine.
If
>
> you want an air-oil separator, look into getting the Walker (Air-Wolf) air-oil
>
> separator.
>
> Gary
>
>
>
>
>
>
>
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>
>
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>
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>
--
Visit our PERSONAL WEBSITE at: http://www.geocities.com/tiger67bravo/
Message 2
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| Subject: | Air-Oil Separator |
--> TeamGrumman-List message posted by: "Mike Lehman" <lehmans@sympatico.ca>
--> TeamGrumman-List message posted by: "Dave" <ddmcknight@alltel.net>
Looking for advice on air-oil separators for a Tiger. I keep the oil at 6
qts.
but still get oil on the belly.
Does the M-20 unit work as advertised??
I appreciate any input anyone can offer.
Dave McKnight
Tiger N880DM
Dave,
Some comments posted to the other Grumman list a while back:
Some thought about what is required to separate oil mist from air provides
insight on how effective the M20 is likely to be and how such a device
should be installed. There are some websites that explain the operation of
demisters (such as those used for aero-derivative industrial gas turbine
engines) but the basic idea is to slow the flow rate and provide surface
area for the mist to coalesces into droplets. (This happens on the inside
surface of our breather hoses and therefore they often drip oil after
shutdown.) Increasing the vent tube diameter will slow the flow and metal
mesh will increase surface contact for the mist. Therefore, the efficiency
of such a passive separator depends on it's size, other design factors
equal. Oil stripped from the vent flow must be collected and then either
stored or drained away.
Sometimes, the drain on demister installations simply can't possibly drain.
Engine breather system pressure decreases from the crankcase
(source)pressure to ambient at the outlet end of the breather tube
(otherwise, there wouldn't be any vent flow out). If a demister is inserted
in the breather line, its internal pressure will be below crankcase
pressure. Now, connect a small demister oil drain tube to the engine
accessory case (or a valve rocker arm chamber) and consider the direction of
flow. The drain tube flow will be out of the engine into the demister same
as via the big breather hose and it will reduce or even prevent collected
oil from flowing the opposite direction back into the engine. This oily
airflow out via the drain tube can be eliminated by looping the line down
well below the connection point on the engine to form an oil trap (like the
sewer gas trap under a sink). Fill the trap with oil on installation
because unless the airflow is stopped, the trap may never fill on its own.
I looked at the M20 at Oshkosh while listening to a Navajo owner ask what's
inside for $400 per engine. I consider the M20 much too small to do much
about reducing vent flow velocity or providing surface area to coalesce oil
mist. I asked about the need to trap the drain tube flow but was dismissed
with words like ' ... that's not how it works ...'. There was clearly no
point
in pursuing a discussion.
I wonder if some of the M20 success stories are due more to improved routing
of the breather hose than to the separator. I'll just keep my large
diameter breather hose sloping upward as much as possible before turning
down to the cowl exit.
Mike
AA-5, no separator
P.S. I've seen the oil consumption of an old Continental reduced
dramatically by simply using an oil filler cap with a crankcase breather
hose added. This reduced the crankcase pressure which reduced the flow
velocity in the hoses (now 2) which reduced entrained oil exiting the
engine.
Message 3
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| Subject: | Re: Air-Oil Separator |
--> TeamGrumman-List message posted by: "flyv35b" <flyv35b@ashcreekwireless.com>
> > Does the M-20 unit work as advertised??
> >
> >
>
> My experience is taht the M-20 doesn't have the volume necessary to be of
> much help. That, and it doesn't have a positive flow back to the engine.
If
> you want an air-oil separator, look into getting the Walker (Air-Wolf)
air-oil
> separator.
>
> Gary
I have to agree with Gary here. I installed a M-20 on a customers plane and
it did not seem to be all that effective. And the unit was mounted as high
as possible and had a downward slope for the drain line all the way. Just
due to the size of the unit and outlet line and the velocity of the air
through the separator it would be very difficult to separate out all of the
oil from the air. Look at the other separators that have been used in the
past and you will see that their volume and the outlet ducts are much
larger.
I think a separator is somewhat of a "Band-Aid" anyhow since an engine with
good ring sealing will have little blowby and not need a separator. I look
at the oil coming out the breather as just another indicator of the engine
condition, along with oil consumption, compression, plug condition, etc. I
also think the M-20 is overpriced for what it is and can do and I'd rather
put the money into new piston rings.
And finally, I'm not all that enthusiastic about returning the separated oil
to the engine sump. From what I've seen it looks pretty bad and I'd just as
soon collect it in a separate container and empty that occasionally.
Cliff A&P/IA
----- Original Message -----
From: <TeamGrumman@AOL.COM>
Subject: Re: TeamGrumman-List: Air-Oil Separator
> --> TeamGrumman-List message posted by: TeamGrumman@aol.com
>
>
> In a message dated 9/6/04 5:34:32 PM, ddmcknight@alltel.net writes:
>
>
> > Does the M-20 unit work as advertised??
> >
> >
>
> My experience is taht the M-20 doesn't have the volume necessary to be of
> much help. That, and it doesn't have a positive flow back to the engine.
If
> you want an air-oil separator, look into getting the Walker (Air-Wolf)
air-oil
> separator.
>
> Gary
>
>
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