REFLECTOR: Fwd: Re: Still test flying...battling high CHT's (Geoff Gerhardt)
Ron N VelocityXLFG
velocityxl at fastmail.fm
Wed Sep 12 07:24:00 CDT 2012
Funny I did the same thing with my radiator to get the air to turn and
use more of the radiator
in the stream.
Ron
On 9/11/2012 8:15 PM, Scott Derrick wrote:
>
> Geoff,
>
> here is a crude drawing, attached
>
> The vanes for number 2 cyl, take up 1/3 of the area of the duct as
> view from the NACA side. same arrangement on the left side for #1..
>
> There are of course two ducts, left and right.
>
> Scott
>
> -------- Original Message --------
> Subject: Re: REFLECTOR: Still test flying...battling high CHT's (Geoff
> Gerhardt)
> From: Geoff Gerhardt <geoff.gerhardt at gmail.com>
> To: Scott Derrick <scott at tnstaafl.net>
> Date: 09/11/2012 10:02 AM
>> Scott,
>>
>> So, do these vanes vertically bifurcate the flow from the runners so
>> that the left half of the flow goes to the most forward cylinder and
>> the right half goes to the most aft cylinder? Or, do you bifurcate
>> it horizontally, the bottom going to the most forward cylinder, the
>> top is then directed aft? Yeah, a picture or rough sketch would help.
>>
>> Thanks.
>>
>> Geoff
>>
>> On Tue, Sep 11, 2012 at 9:25 AM, Scott Derrick <scott at tnstaafl.net
>> <mailto:scott at tnstaafl.net>> wrote:
>>
>> Geoff,
>>
>> I will make a drawing on how I did the turning vanes, there
>> is no way to get a picture. basically you have two rectangular
>> feed tubes from the NACA into the plenum. My two vanes start
>> inside the feed tubes, thats where they are riveted too. They
>> are bent in a curve to end up where I want them. They reach all
>> the way down to the upper fins of the cylinders. I split a small
>> fuel line and glued that to lower edge of the vane so they don't
>> scratch or cut any of the tubes, wires or fins down in there.
>>
>> Yes the gap is where the plenum comes up against the forward
>> side of the cylinders. I just silly-coned a piece of foam in
>> between the cyl and plenum to hold it out. I ended up leaving it
>> in there, for the last 100 hours! I siliconed fiberglass to my
>> lower cylinder fins to force the air though them as you did with
>> aluminum. I left those in place, don't remove them! The gap
>> causes a low pressure to form which encourages the air to make
>> the turn down through the cyl instead of going straight back to
>> the back cyls. Somebody on this list told me about this trick,
>> he deserves the credit.
>>
>> I also suffered the pusher streak! Oil breather oil on the
>> lower cowl and prop. What a Pita. I wiped that streak off for
>> 700 hours! Now I have a super clean lower cowling!
>>
>> I had Custom Aircraft weld in a 1/2 inch nipple to the left
>> hand stack which I attached the breather hose to. Now the little
>> bit of oil that can make such a nasty long streak and vapor gets
>> partially burned and thrown away from the cowling. I've attached
>> Clinton's diagram he sent me after I talked to him about it.
>>
>> Scott
>>
>> -------- Original Message --------
>> Subject: Re: REFLECTOR: Still test flying...battling high CHT's
>> (Geoff Gerhardt)
>> From: Geoff Gerhardt <geoff.gerhardt at gmail.com>
>> <mailto:geoff.gerhardt at gmail.com>
>> To: Scott Derrick <scott at tnstaafl.net> <mailto:scott at tnstaafl.net>
>> Date: 09/10/2012 03:04 PM
>>> Scott,
>>>
>>> If you have some pictures of your turning vanes, I'd much
>>> appreciate them. I'm envisioning curved aluminum bits riveted
>>> to the top of the plenums that direct air flow down to the two
>>> fore cylinders.
>>>
>>> I've seen you mention before about opening up a gap along the
>>> side of #2. On a Lycoming 1&2 are the aft cylinders, so that
>>> didn't really make sense to me, but now I see that for you
>>> (Continental?), 1&2 cylinders are your fore cylinders. I wonder
>>> if opening up that gap draws more air to make that sharp turn.
>>> I've got my plenums up tight to the wall of my 3&4 cylinders.
>>> I also have aluminum extensions to my plenums that wrap around
>>> the cylinders to make sure air is forced thru the fins. Perhaps
>>> I should open those up a bit. I can't completely rationalize
>>> how that helps, but it seems to have made a difference for you.
>>>
>>> One thing that may have nothing to do with this, but I've found
>>> interesting...My oil vent line is in the center of the fuselage
>>> right where the cowling meets the firewall. I typically see a
>>> nice brown streak running up the cowling right to the furthest
>>> aft end. I've also found that oil collects right under the prop
>>> extension. Initially, I thought that I had a seal leak or the
>>> crank expansion plug was leaking, but it turns out that the oil
>>> from the vent is turning the corner and running inside the
>>> cowling and pooling right under the prop extension. Does that
>>> say anything about a vacuum being created there? Good or bad?
>>> Does this happen to everyone?
>>>
>>> I think I'm going to start by adding taller VG's a bit further
>>> forward (maybe 4" like you suggest) of the NACA's. Right now I
>>> have relatively low profile ones right before the NACA's.
>>>
>>> Geoff
>>>
>>>
>>> On Mon, Sep 10, 2012 at 12:27 PM, Scott Derrick
>>> <scott at tnstaafl.net <mailto:scott at tnstaafl.net>> wrote:
>>>
>>> Geoff,
>>>
>>> I felt like my battle of the CHT's was legend!
>>>
>>> I have 5/8 VG's about 4 inches forward of the roof NACA,
>>> I thought I got 5-10 degrees better cooling from them.
>>>
>>> I have turning vanes in my plenum for #1 & #2 cylinders,
>>> those are the forward as in nearest to the firewall
>>> cylinders. Normally I've been told those are the warmest
>>> because the air has to make a dramatic turn to go through
>>> them. I have two vanes for each cylinder, one ends halfway
>>> across the cylinder, the other right between the cylinder
>>> and the next cylinder. I think that dropped the temps on
>>> those two cylinders about 5-10 degrees.
>>>
>>> I opened a gap in the plenum in front of #2(right
>>> front). That helped #2 about 5-10 degrees.
>>>
>>> I installed a cowl flap(which I didn't need when I had
>>> the IO360, that helped about 15-20 degrees.
>>>
>>> Now I can climb out full power and not hit 400 unless
>>> the oat is above 90F. In the winter I have trouble keeping
>>> the temps up, range is 290-320 in the coldest days.
>>>
>>> I cruise max throttle LOP 360-330, near max throttle ROP
>>> 390-360 in the summer. Max throttle ROP exceeds RPM
>>> redline, so I don't do that much.
>>>
>>> Scott
>>>
>>> -------- Original Message --------
>>> Subject: Re: REFLECTOR: Still test flying...battling high
>>> CHT's (Geoff Gerhardt)
>>> From: Geoff Gerhardt <geoff.gerhardt at gmail.com>
>>> <mailto:geoff.gerhardt at gmail.com>
>>> To: Velocity Aircraft Owners and Builders list
>>> <reflector at tvbf.org> <mailto:reflector at tvbf.org>
>>> Date: 09/10/2012 07:52 AM
>>>> Fred,
>>>>
>>>> Yes, this is a new engine, so I'm guessing that's part of
>>>> the reason, but I don't like having one cylinder being that
>>>> much higher than the other three. I have VG's about where
>>>> you suggested putting them, an inch or so ahead of the NACA
>>>> entrance. Because I'm having problems primarily on climb
>>>> out, I'm thinking I should move them fore a few inches.
>>>> Also, the VG's I'm using are relatively low profile (<1/2"
>>>> high). I think I'll make some taller ones and see if that
>>>> helps, too.
>>>>
>>>> Thanks for the suggestions.
>>>>
>>>> Geoff
>>>>
>>>> On Mon, Sep 10, 2012 at 9:23 AM, Fred Anderka
>>>> <fred at holohil.com <mailto:fred at holohil.com>> wrote:
>>>>
>>>> Geoff:
>>>>
>>>> Had similar CHT problems with the IO-550, particularly
>>>> cylinder #2. There are deflector plates between the
>>>> cylinders that can be bent to change the air flow, have
>>>> not messed with them though. Trying to put deflectors
>>>> on top of that engine would be a nightmare with all the
>>>> plumbing that is on top of that engine. Is this is a
>>>> new engine? I have been told that the CHT's will
>>>> decrease as the engine breaks in. This is also a scary
>>>> portion of your flight testing if you follow engine
>>>> manufacturers reccommendations. The engine
>>>> manufacturers recommend that for proper break in of the
>>>> engine it should be operated near maximum power for the
>>>> first 20-25 hours. Continued low power operation will
>>>> glaze the cylinders resulting in high oil consumption.
>>>> I suppose 25 hours of touch and go's might qualify.
>>>>
>>>> Place a pair of VG's 1 1/2" ahead of the start of the
>>>> slope of the NACAs. You will see a dramatic decrease
>>>> in the CHT's to the point where I am trying to figure
>>>> out a way to reduce the air flow in the winter or when
>>>> flying at very cold altitudes. Scott suggested making
>>>> the ramp of the NACAs adjustable to reduce the size of
>>>> the air intake. The VG's pressurize the plenum to a
>>>> point where I have also noticed an increase in manifold
>>>> pressures during climb out. The Continental gets it's
>>>> combustion air from the back of the engine plenum.
>>>>
>>>> Fred
>>>> XL-RG (620 hrs.)
>>>>
>>>>
>>>> Date: Sun, 9 Sep 2012 20:08:51 -0400
>>>> From: Geoff Gerhardt <geoff.gerhardt at gmail.com
>>>> <mailto:geoff.gerhardt at gmail.com>>
>>>> To: Velocity Aircraft Owners and Builders list
>>>> <reflector at tvbf.org <mailto:reflector at tvbf.org>>
>>>> Subject: REFLECTOR: Still test flying...battling high CHT's
>>>>
>>>> All,
>>>>
>>>> Just an update on my test flying. I've got just over
>>>> 9hrs in now. I have been battling high CHT's, making a
>>>> few changes. I had a fuel flow imbalance that was
>>>> causing some problems (hot #2) - I think it was a
>>>> partially blocked injector. I took all the
>>>> injectors/lines out and cleaned them and balanced the
>>>> flows (mixed and matched injectors until all injectors
>>>> were putting out the same flow. Now, in cruise, all
>>>> cylinders are pretty close and reasonably cool (or, I
>>>> guess, not overly hot). Once I get to cruise, they all
>>>> sit <380F. But, on climb out, #3 gets way too hot
>>>> (420F) forcing me to reduce power and bring the nose
>>>> down so I'm climbing at <500FPM at ~60% power, 100kts.
>>>> But, once I get to cruise and can bring the nose down
>>>> and get the speed up, it behaves. Still the hottest,
>>>> but it'll sit around 380F. So, I'm thinking I have to
>>>> work on my cooling plenums. #4 will get hot too, but
>>>> it doesn't get much over 400F.
>>>>
>>>> Has anyone had success putting deflectors in the
>>>> plenums to direct air flow to cyls 3/4? Or, maybe VG's
>>>> in the entrance of the runners to keep the airflow
>>>> better attached to the bottom of the runner so it can
>>>> turn the corner down to cool 3/4 (I have VG's before
>>>> the NACAs)?
>>>>
>>>> Part of the issue may be my cruise prop - I need to
>>>> keep full power on to get a decent climb rate.
>>>>
>>>> Thanks.
>>>>
>>>> Geoff
>>>>
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>>>
>>> --
>>> What the superior man seeks is in himself; what the small man seeks is in others.
>>> Confucius
>>>
>>>
>>
>> --
>> What the superior man seeks is in himself; what the small man seeks is in others.
>> Confucius
>>
>>
>
> --
> He who knows others is wise;
> He who know himself is enlightened.
> Lao-tzu
>
>
>
>
>
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