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pitts_pilot(at)bellsouth.
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 Posted: Wed Feb 08, 2006 7:18 pm Post subject: Varnatherm |
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I posted this back to the list because there's some good info others may
like ... but I'm going to do the 'do not archive' because it's probably
already there.
Mannan J. Thomason wrote: (offline)
| Quote: | Linn, Jerry
I just assymbled my IO-360 last fall and was trying to figure out how
that darn thing works. When I heated the vernatherm, it expanded out
to make itself longer. It appears to me that when the engine gets hot
the vernatherm expands out to contact the seat in the accessory case,
which then sends oil through the oil cooler. It looks to me like the
oil circulates in the engine untill it reaches the temp stamped on the
vernatherm at which time it expands to send oil to the cooler to keep
the oil temp regulated.
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Bingo! You did good!!!
| Quote: | I would guess that if the engine never got hot enough, (ie: winter)
the vernatherm might never expand out to contact the seat therefore
not disturbing any ink marks on the cone.
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True on the surface. I'm in FL, and we don't have that problem!!! If
you're sure you have a good oil temp gauge, you might tape off portions
of the cooling air intake a little at a time to check in the frozen
nawth. In my experience, most cooling air intakes are too large anyway,
and they just add more cooling drag. The only way to know if your
inlets/outlets are sized correctly ios to do the manometer test .....
and you'll have to go to the archives to get that. It's involved.
| Quote: | I do know that when new, the vernatherm will expand at about the temp
stamped on it. I'm no engine expert, so you might verify my theory
with someone who knows for sure.
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Your theory is spot on. the only problem with Vernatherms is that they
stick when they get really old an abused.
Linn .... workshop walls and roof going on this week!!!
| Quote: |
Mannan Thomason
RV-8 Cowl and Spinner. Almost ready to crank & taxi!
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Dale Ensing
Joined: 11 Jan 2006
Posts: 571
Location: Aero Plantation Weddington NC
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| Posted: Thu Feb 09, 2006 9:16 am Post subject: Varnatherm |
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The posting by linn Walters regarding operation of the Varatherm reminded me of a recent experience with an initial run of a engine that I think is worth passing along to the those who have not yet run their engines
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_________________
Dale Ensing
RV-6A
Aero Plantation
Weddington NC |
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BPA(at)bpaengines.com
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| Posted: Thu Feb 09, 2006 9:40 am Post subject: Varnatherm |
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You are correct Dale in that an oil line leak from the cooler would not
be found until the Vernatherm opens. The vernatherm is supposed to open
(53E22144)which is the current Lycoming vernatherm when oil temp reaches
187-189 F. Not to be alarmed but when the vernatherm opens there will be
a slight drop in pressure, usually 3-5 lbs.
Allen Barrett
BPE, Inc.
www.barrettprecisionengines.com
--
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13brv3
Joined: 11 Jan 2006
Posts: 76
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| Posted: Thu Feb 09, 2006 3:43 pm Post subject: Re: Varnatherm |
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I'm glad this came up, because I've never quite understood how this little gizmo worked. Now that I think I understand it, I'm left with another puzzle.
Why do people go to the trouble to block off part of their oil cooler in the winter? If this thermostat only opens when the temp is too high, then it will only flow oil through the cooler until the temp comes down. The effectiveness of the cooler will change the amount of oil that needs to flow through it to bring down the temp, but still, the thermostat will control it. Why would you need to cover part of the cooler then?
Color me confused...
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pitts_pilot(at)bellsouth.
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| Posted: Thu Feb 09, 2006 5:05 pm Post subject: Varnatherm |
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I believe that even with the vernatherm 'open' (returning oil to the
case), some oil still flows through the oil cooler due to pressure
differences. However, I think it'll just take longer for the engine to
get up to temp without the tape. It would be more efficient to block
off the air intake a little ..... but slapping duct tape over the inlets
would be a little unsightly. One other cold weather option would be to
hinge the lower cowl at the cooling air exhaust opening to control the
air flow that way. Just a thought.
Linn
do not archive
13brv3 wrote:
| Quote: |
I'm glad this came up, because I've never quite understood how this little gizmo worked. Now that I think I understand it, I'm left with another puzzle.
Why do people go to the trouble to block off part of their oil cooler in the winter? If this thermostat only opens when the temp is too high, then it will barely be putting any oil through the cooler anyway.
Color me confused...
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=11138#11138
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Rick Galati
Joined: 10 Jan 2006
Posts: 91
Location: Lake St. Louis MO.
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| Posted: Fri Feb 10, 2006 4:28 am Post subject: Re: Varnatherm |
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| Quote: | | Why do people go to the trouble to block off part of their oil cooler in the winter? If this thermostat only opens when the temp is too high, then it will barely be putting any oil through the cooler anyway.olor me confused... |
Some production airplanes including Warriors and Cherokees use a bolt-on winterization plate to completely block off the frontal area of the oil cooler for winter operations. In fact the 0-320 equipped 1974 Piper Warrior's oil cooler is mounted exactly the same way my plans mounted cooler is and it has a permanently mounted back plate installed!
The baffle mounted oil cooler supporting my 0-320 would barely attain 170 degrees in the hottest of summer weather. Through trial and error experimentation, I eventually blocked off the entire back side of the oil cooler with a plate. This finally brought the temp up to 180-185 degrees. Even so, when winter arrived, the oil temp barely rose to 130 degrees so I blocked off the frontal area of the cooler like the aforementioned production planes. Then when a brief winter temperature inversion occurred around here, I had to remove it to keep from generating too hot oil temperatures. This is precisely why I purchased the oil cooler vent/shutter from Van's. http://tinyurl.com/9xh9k Adjustable from the cockpit, this device should put an end to constant tweaking of the oil cooler to compensate for seasonal (or daily) weather changes.
Rick Galati RV-6A "Darla" 108 hours
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Last edited by Rick Galati on Sat Feb 11, 2006 4:33 am; edited 1 time in total |
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dbris200(at)sbcglobal.net
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| Posted: Fri Feb 10, 2006 9:06 am Post subject: Varnatherm |
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The Vernatherm does not block flow to the cooler, it's an oil cooler
BYPASS valve. It's in parallel with the cooler, so when it's open the
oil goes whichever direction is easiest. When it's closed (hot oil) it
forces the oil through the cooler. So, oil is always able to go to the
cooler and some always does, hence the reason for blocking the air to
the cooler.
Dave -6, So Cal
EAA Technical Counselor
13brv3 wrote:
| Quote: |
I'm glad this came up, because I've never quite understood how this little gizmo worked. Now that I think I understand it, I'm left with another puzzle.
Why do people go to the trouble to block off part of their oil cooler in the winter? If this thermostat only opens when the temp is too high, then it will barely be putting any oil through the cooler anyway.
Color me confused...
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=11138#11138
|
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larywil(at)comcast.net
Guest
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| Posted: Fri Feb 10, 2006 5:41 pm Post subject: Varnatherm |
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Hi gang,
The current explanations of the vernatherm have been the best in several
years. This subject always comes up in cold weather, and several of our
listers really do know how it works. Todays posts from Jeff Dowling and
Dave Bristol seem to explain the operation of the v/t properly and concisely.
I would like to add a bit of information if I may. I don't remember the RV
type of the original posters question, but if it was an RV-4 ...... What
else can I say. Every RV-4 wants to run at ~ 120 -130 deg. in the winter.
On a miserable, hot summer day, we are lucky to see 195-200 deg. The very
tight cowling on the -4 is overkill to the cooler, and the explanation
about the bypassing of the oil seems to explain and confirm why the --4's
oil temp is so low. I have had several RV-4's and have seen and performed
several experiments. My current -4 has its cooler mounted to the rear
baffle, and has a controllable flap on the rear(exhaust side) of the
cooler. This has never, never worked well. In fact, it doesn't work at all.
Because at normal flying speed, the air pressure entering the intake side
of the cooler is so strong, it pushes the flap open a millimeter or two.
This is enough to over-cool the oil. HOWEVER, on both my -4's the solution
that always works is to partially or completely cover over the intake side
of the cooler.
PS Thanks Jeff and Dave.
-
Louis I Willig
1640 Oakwood Dr.
Penn Valley, PA 19072
610 668-4964
RV-4, N180PF
190HP IO-360, C/S prop
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