Today's Message Index:
----------------------
1. 05:41 AM - Re: RotaxEngines/Bing carb's alleged altitude compensation (rampil)
2. 05:51 AM - Re: Rotax 912 oil analysis (rampil)
3. 06:06 AM - Re: New Cylinder heads temperature sensors and matching Temperat (rampil)
4. 06:10 AM - Re: Variable Oil Pressure Reading (rampil)
5. 06:10 AM - Re: Re: RotaxEngines/Bing carb's alleged altitude compensation (Lowell Fitt)
6. 07:16 AM - Re: Re: Variable Oil Pressure Reading (FLYaDIVE)
7. 07:30 AM - Re: RotaxEngines-List Digest: 1 Msgs - 06/19/17 ()
8. 05:57 PM - Re: Variable Oil Pressure Reading (rampil)
9. 06:23 PM - Re: Variable Oil Pressure Reading (JohnF)
10. 07:12 PM - Re: Re: Variable Oil Pressure Reading (FLYaDIVE)
Message 1
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| Subject: | Re: RotaxEngines/Bing carb's alleged altitude compensation |
Interesting that this old canard about altitude compensation is raising
it's head from the dead again. It is, basically a false claim, unless, as
Creighton points out you restrict your flying to Piper cub altitudes. Fuel
consumption, I believe, is most relevant during cross country ops, and
during XC ops, I usually plan FL060-090 over the flatlands I now live
amidst. As they say, if you plan 500' AGL (1500' MSL here), your mileage
may vary!
When my Europa was freshly built 13 years ago and my engine
fully instrumented, I ran extensive test cards on engine performance
while flying off my Phase 1 at Z-Hills. Climbing above 3-4,000 DA, fuel
consumption rises reliably, while effective power declines as expected.
I published the spreadsheets here on the Matronics forums at the time
and shared them with Phil Lockwood. Shortly after that, Rotax stopped
advertising this "feature". Coincidence? Perhaps.
Rather than theory from possibly commercially informed interests,
I would prefer more actual measurements, preferably from
disinterested but experienced third parties. If there is confusion about
the Bing system, consider the role that Rotax played.
Despite the advertising, the official operator's manual provides
essentially no performance / consumption data compared with
Lyc / Con manuals.
I still love my 912s, but I am a bit steamed that my block cracked at
380 hours of operation and despite some discount, my repair bill was over $10k.
--------
Ira N224XS
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=470260#470260
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| Subject: | Re: Rotax 912 oil analysis |
Oil analysis in Rotax engines is difficult to assess since Rotax
refuses to provide either normative data or metallurgical content data
for components to use for diagnosis should a particular ion spike.
--------
Ira N224XS
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=470263#470263
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| Subject: | Re: New Cylinder heads temperature sensors and matching |
Temperat
Hugh,
It would help to know if the sensors are thermocouple or resistive,
for example. All TC type "K" senders (yellow/red) should work with
all type K gauges unless the wire length is much different than the gauge
expects. Use a VOM to measure the resistance of the probe and compare it
to what should be stamped on the back of the gauge.
If you have resistance type probes, they usually require a matched set
of probe/gauge.
--------
Ira N224XS
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=470265#470265
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| Subject: | Re: Variable Oil Pressure Reading |
I could be wrong about this, but a small bubble is far more likely
to smooth out dynamic swings in pressure than to create them. Think
plumbing water hammer arrestor (a pipe length full of air).
Do these oil pressure changes depend on oil temperature (as they normally
do)?
--------
Ira N224XS
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=470266#470266
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| Subject: | Re: RotaxEngines/Bing carb's alleged altitude compensation |
Interesting post. My understanding was That the altitude compensation was
in fact, related to the Cub altitudes. The memory comes up as we, on our
way home from an Idaho Back Country adventure in our Kitfoxes, flying the
bends of a river at 100 ft. looking for wildlife and practicing steep
turns, we listened to the chatter coming from a group of RVs on their way
to the Reno Air Races, while flying at RV altitudes. all the talk was
about manifold pressure and airspeed. To each his own, I guess.
Lowell
On Jun 20, 2017 5:46 AM, "rampil" <ira.rampil@gmail.com> wrote:
>
> Interesting that this old canard about altitude compensation is raising
> it's head from the dead again. It is, basically a false claim, unless, as
> Creighton points out you restrict your flying to Piper cub altitudes. Fuel
> consumption, I believe, is most relevant during cross country ops, and
> during XC ops, I usually plan FL060-090 over the flatlands I now live
> amidst. As they say, if you plan 500' AGL (1500' MSL here), your mileage
> may vary!
>
> When my Europa was freshly built 13 years ago and my engine
> fully instrumented, I ran extensive test cards on engine performance
> while flying off my Phase 1 at Z-Hills. Climbing above 3-4,000 DA, fuel
> consumption rises reliably, while effective power declines as expected.
> I published the spreadsheets here on the Matronics forums at the time
> and shared them with Phil Lockwood. Shortly after that, Rotax stopped
> advertising this "feature". Coincidence? Perhaps.
>
> Rather than theory from possibly commercially informed interests,
> I would prefer more actual measurements, preferably from
> disinterested but experienced third parties. If there is confusion about
> the Bing system, consider the role that Rotax played.
>
> Despite the advertising, the official operator's manual provides
> essentially no performance / consumption data compared with
> Lyc / Con manuals.
>
> I still love my 912s, but I am a bit steamed that my block cracked at
> 380 hours of operation and despite some discount, my repair bill was over
> $10k.
>
> --------
> Ira N224XS
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=470260#470260
>
>
Message 6
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| Subject: | Re: Variable Oil Pressure Reading |
Ira:
You are correct, you are Wrong!
Air, Gases are COMPRESSIBLE! Liquids are NON-COMPRESSIBLE.
Liquids will transmit pressure equally in ALL directions and at the same
pressure even through different/mixed size hoses. Physics - Fluid Dynamics
101.
Air on the other hand is compressible and also expandable and will expand
and compress CHANGING its volume and pressure - Boyle's Law also a part of
Physics 101.
So, the air bubble will cause the transducer and/or the gauge to pulse.
Barry
On Tue, Jun 20, 2017 at 9:10 AM, rampil <ira.rampil@gmail.com> wrote:
>
> I could be wrong about this, but a small bubble is far more likely
> to smooth out dynamic swings in pressure than to create them. Think
> plumbing water hammer arrestor (a pipe length full of air).
>
> Do these oil pressure changes depend on oil temperature (as they normally
> do)?
>
> --------
> Ira N224XS
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=470266#470266
>
>
Message 7
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| Subject: | Re: RotaxEngines-List Digest: 1 Msgs - 06/19/17 |
John F,
Once you break open the oil system (such as to replace oil hoses) on a Rotax
Engine you introduce the possibility of entrapped air if you do not vent or
"purge" the system after refilling the system with new oil per the Rotax
instructions in their engine installation manual. You should not operate the
engine until the system has been vented. See instructions on page 36 of the
installation manual Edition 2 of 1997 03 26 or later editions.
Hugh G. McKay III, P.E. Fellow, L.M. ASCE
Senior Consultant
Worldwide Engineering Inc.
4090 North NC Hwy. 16
Denver, NC 28037
Ph. 704-661-8271
Fax 704-483-5466
email hgmckay@bellsouth.net
http://www.wwegeo.com
-----Original Message-----
From: RotaxEngines-List Digest Server
Sent: Tuesday, June 20, 2017 3:03 AM
Subject: RotaxEngines-List Digest: 1 Msgs - 06/19/17
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Today's Message Index:
----------------------
1. 06:35 PM - Variable Oil Pressure Reading (JohnF)
________________________________ Message 1
_____________________________________
Time: 06:35:58 PM PST US
Subject: RotaxEngines-List: Variable Oil Pressure Reading
From: "JohnF" <n29cx@ridgeviewtel.us>
I just changed the oil lines on the Rotax in my RV-12 and now see oil
pressure
varying from 33 psi to 60 psi. I moves around like that in flight.
I wonder if air is in the oil line to the oil pressure sensor...if so how to
check
and bleed it out since it goes to a 'dead-end' at the sensor.
Best I can think of is to open that line and let oil run out and quickly
replace
the oil line to the sensor in the hope that the air bubble will be gone
Your ideas?
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=470251#470251
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| Subject: | Re: Variable Oil Pressure Reading |
Hey Barry,
You are right about the static situation, it's a bit different dynamically.
Back in the day when I used to teach about the fluid dynamics
of invasive arterial blood pressure, I would note that
the distortion or "ringing" in the system was related to the
resonance of the system which in turn is a function of the
compliance of the tubing plus air bubbles, and the inertance
of the fluid column. When the driving frequency(pulsation of the
oil pump) gets close to the system's resonant frequency, the pressure
Oscillates wildly ( in a measurement system that has adequate frequency
response).
I will generalize (and guess) a bit to say that
1) the driving frequency of the oil pump, a multiple of RPM
is way higher than the responsiveness of mechanical
Oil pressure gauges to track the waveform even though you
would be able to see the ringing with an electronic transducer
and an o-scope.
2) air (increasing compliance) decreases the resonant
freq of the tubing system thus reducing the apparent
Oscillation on the gauge by pushing the resonant frequency
of the tubing well below the rpm harmonic.
--------
Ira N224XS
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=470292#470292
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| Subject: | Re: Variable Oil Pressure Reading |
I am the OP....I suspect I have found the problem and will know tomorrow when I
button up the plane and do a run up or perhaps a short flight. I will post my
results. I doubt that it will involve anything very exotic, but we'll see.
JohnF
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=470295#470295
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| Subject: | Re: Variable Oil Pressure Reading |
Ira:
Sorry to say teach, wrong guess!
Well, not a guess, just over thinking a simple situation.
What about open and closed end resonance of the oil lines?
What about cavitation cause by bubbles in a bend, or the reduced flow
especially at 90 Deg bends.
If you want to prove my reasoning true or disprove yours just add a length
of oil line. That will change the 'frequency' as you stated and if you are
correct. The pulsing will go away.
But, if you are wrong and if the air bubble remains then the problem will
continue and your theory is proven wrong.
Think of it this way: Why does Rotax make a big deal about 'Burping' the
system? Because air bubbles cause all these types of problems. If what
you say is true, then there would be hundredths of plane owners complaining
about the same problem. Both with and without Rotax engines.
Get rid of the air and the problem goes with it!
K.I.S.S. M.E.!
Barry
QA Engineer that punched holes in theories.
On Tue, Jun 20, 2017 at 8:57 PM, rampil <ira.rampil@gmail.com> wrote:
>
> Hey Barry,
>
> You are right about the static situation, it's a bit different dynamically.
> Back in the day when I used to teach about the fluid dynamics
> of invasive arterial blood pressure, I would note that
> the distortion or "ringing" in the system was related to the
> resonance of the system which in turn is a function of the
> compliance of the tubing plus air bubbles, and the inertance
> of the fluid column. When the driving frequency(pulsation of the
> oil pump) gets close to the system's resonant frequency, the pressure
> Oscillates wildly ( in a measurement system that has adequate frequency
> response).
>
> I will generalize (and guess) a bit to say that
> 1) the driving frequency of the oil pump, a multiple of RPM
> is way higher than the responsiveness of mechanical
> Oil pressure gauges to track the waveform even though you
> would be able to see the ringing with an electronic transducer
> and an o-scope.
> 2) air (increasing compliance) decreases the resonant
> freq of the tubing system thus reducing the apparent
> Oscillation on the gauge by pushing the resonant frequency
> of the tubing well below the rpm harmonic.
>
> --------
> Ira N224XS
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=470292#470292
>
>
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