Today's Message Index:
----------------------
1. 03:48 AM - Re: the Obsidian Files - So Much Noise!!! (clivesutton)
2. 06:49 AM - Re: the Obsidian Files - So Much Noise!!! (Area-51)
3. 08:14 AM - Re: October 2022 Zoom Episode 1 (Monoman)
4. 10:26 AM - Re: the Obsidian Files - So Much Noise!!! (clivesutton)
5. 03:45 PM - Re: the Obsidian Files - So Much Noise!!! (Area-51)
6. 07:07 PM - Re: Re: the Obsidian Files - So Much Noise!!! (Bud Yerly)
Message 1
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| Subject: | Re: the Obsidian Files - So Much Noise!!! |
Hi Area-51, I follow your posts with much interest - not least because you have
a handle on the engineering physics as evidenced by your simulation images.
I was going to say that whilst adding mass coating is one route to improvement
(Bergers Law 1911), isn't a set of noise-cancelling headphones a more optimum
or at least, initial, route to achieve the same thing - and at less weight gain?.
Not a criticism, just interested to know why the additional mass route. It will
work if you add enough mass, but the carb rubber wear/unknown fire risk increase
and general weight penalty does seem a bit onerous.
That said, the tinkering/problem-solving with these things is almost as much fun
as the flying, of course !
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=510462#510462
Message 2
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| Subject: | Re: the Obsidian Files - So Much Noise!!! |
These are great discussion points, so let's break them down a bit...
The weight penalty factor v's noise cancelling headphones:
I've added 1000g stationed 50mm ahead of the firewall; my W&B has been marginally
affected... The Bose Active X headsets weigh 0.485kg (1.1kg with carry case),
the Clarity Aloft weigh 0.135kg (0.320kg with carry case)... The AUW penalty
is now the added mass less the gain; we are now at around 0.4kg weight penalty...
but hang on a minute, let's now fly two up! Bose headsets with carry cases
2.2kg, Airbox mod with Clarity Aloft headsets and carry cases 1.75kg... just
lost 0.45kg!! ... thats two more $100 hamburgers!!
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=510463#510463
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| Subject: | Re: October 2022 Zoom Episode 1 |
rparigoris wrote:
> Hi Group
>
> Here's links to March 2023 Zoom Episode 5 about Fuel Sender Operation and Repair:
> https://1drv.ms/u/s!Ah1S270Nwg9Vgfx9spnrAw9ZaL5m7w?e=12nuwO
>
> For whatever reason, Matronics always cuts off some of the hyper-link when I
post links. Just copy the entire link and paste into URL of browser.
>
> ** If buffering occurs when viewing mp4 video, open the settings icon and reduce
resolution. The settings icon is a gear with a hole in it located on bottom.
>
> Ron and Wayne
Just wanted to say how interesting this video was, completely fascinating stuff
regarding the Apollo programme. Thanks for posting.
My father mentioned that back in the late 50's they used an English Electric Saturn
analogue computer to simulate nuclear reactor fault conditions. It was a
hard wired structure that entirely filled two floors of the building they worked
from! Changed days.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=510464#510464
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| Subject: | Re: the Obsidian Files - So Much Noise!!! |
Thanks for your reply and i do understand your reasoning.
In the Automotive world (based upon ~20+ years in hands-on NVH development there),
the other issues were 1) moving the resonating cavity/intake openings as far
away as possible from the operators ear - usually to the front of the engine
bay, as, like reductions from mass damping, distance makes about the same difference
in attenuation (double the distance, halve the sound power), and 2) working
to try and tune the intake pipework so that it does not resonate at the
typical cruise engine RPM. Most cars have intake resonators that take this problem
away - some of them are even closed-loop, measuring the tone and then adjusting
the effectiveness of the anti-resonator to minimise it.
I wish we had the freedom to tinker here in the UK that you have - changing a nut
and bolt can invoke cries for the mandatory need for a scrutinised MOD required,
here.
And I dearly wish i still had access to the rather expensive test equipment i could
get my hands on back then, a Campbells diagram [Sound level or Vibration
amplitude vs both RPM and frequency scales - for both engine Vibration and emitted
noise vs RPM for e.g. a Rotax engine installation in a Europa], could tell
us all so much - why exhaust springs break so easily, why the noise in the cabin
is what it is, and what the optimum engine RPMs would be to minimise those
etc.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=510465#510465
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| Subject: | Re: the Obsidian Files - So Much Noise!!! |
Oh woww!! Excellent... I totally agree with everything you have imparted... The
job is yours, you're hired; report back in month's time
Where can we liberate this said test equipment from???? We need to know where to
put the Helmoltz resonator!!
Flew again today; the results are very consistent.. next stage is an internal baffle
for the air box... an extended forward running induction tube was considered
however this would end with the inlet port facing forward instead of upward;
so any noise emissions would be directed out front like an air horn as apposed
to an upwards direction away from the ground below. However so far i am totally
satisfied with the result as is, but will take it further with the internal
baffle and hear what happens
Any technical comments toward the "shut that noise up" project is helpful for Europans..
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=510467#510467
Message 6
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| Subject: | Re: the Obsidian Files - So Much Noise!!! |
As Clive alluded to, resonance in the opposed 4 banger exhaust is an issue as well
as intake. The thin fiberglass footwell directly under the feet of the pilot
or passenger, especially in the Classic with the exhaust pipe exiting directly
aft under the pilots feet, resonates something fierce and sounds just like
the carb inlet. Creighton Smith's 96EG underwent a surgery of the heavy Classic
Exhaust and the aft lobe was removed, and a straight pipe added. What a
racket that made initially. We changed the tuning length and put in an expansion
pipe (nothing sophisticated, just cut the pipe and put a wider pipe on the
end to change the note). Creighton was a motorcycle racer, and he did an excellent
job softening the sound. What a difference. Still louder than my 914
but it didn't bring the airport to a stop on ground runs any more.
Prop pressure pulses across the aircraft windscreen in the Europa are not that
bad, so I have not been concerned with that as in other light aircraft. However,
any looseness in the doors hinges, latches and the D panel in the back are
very large drum skins and the low frequency drone is annoying enough and fatiguing,
but the rattle is irritating beyond description. Prop power pulses as
I call them, is normally not bad on a three blade that is tapered. The two blade
wide chord blades can definitely be felt and heard as even the XS nose tends
to transmit some of that back to the cockpit.
Personally, having a 914 and leather interior makes most of my aircraft remarkably
quiet on the inside. The 912S and 912 versions I tend to prefer a rework
of the inlet air geometry to break up the intake noise and as far as the exhaust
note, I leave it to Robin at CKT Engineering for the 912S exhaust note. It
is amazing what a bad baffle in the exhaust sounds like. Many don't realize
they have a bad silencer baffle. CKT has done a nice, but expensive, Rotax 912
down pipe exhaust and side exit that makes the little fart can engine sound
very quiet. My opinion for what that is worth.
Noise is fatiguing. ANR helps the ears, but the vibration of the various noises
hitting the body is fatiguing. The Europa has that phenolic type firewall that
is very thick and I do not do any heat or soundproofing on it. I do add a
thin stainless steel plate some 4-6mm proud of the pilots footwell on some of
the 914s as this cuts the heat on the feet. Proper air venting is needed down
here in the South. I will not do a painted only interior because it is loud
and sound bangs around all through the cockpit with nothing to absorb it. I
do not do any firewall sound proofing on a trigear because I build in a firewall
aft of the nose gear covered with firewall 2000 (excellent fire and sound proofing).
The mono is a different animal. I find the metal firewall an excellent
sound transporter and amplifier. The airflow through the slots is also a
bugger. I have tried the soft and hard Lord mounts and frankly didn't see any
change in apparent vibration (purely measured by feel) Props make a difference
as does exhaust plumbing and support. Nothing worse than an exhaust system
in contact or firmly attached to the frame on a 912S. The 914, you don't have
a choice on the mounting. But in its 15-20 years it has had a few turbo support
cracks repaired.
One of the reasons I went with the stock kit. Experimenting to fix issues is time
consuming/expensive and well, an experiment, sometimes it works, sometimes
it doesn't and hopefully, it doesn't add weight.
Keep up the good work.
Bud Yerly
-----Original Message-----
From: owner-europa-list-server@matronics.com <owner-europa-list-server@matronics.com>
On Behalf Of Area-51
Sent: Saturday, March 18, 2023 6:45 PM
Subject: Europa-List: Re: the Obsidian Files - So Much Noise!!!
Oh woww!! Excellent... I totally agree with everything you have imparted... The
job is yours, you're hired; report back in month's time
Where can we liberate this said test equipment from???? We need to know where to
put the Helmoltz resonator!!
Flew again today; the results are very consistent.. next stage is an internal baffle
for the air box... an extended forward running induction tube was considered
however this would end with the inlet port facing forward instead of upward;
so any noise emissions would be directed out front like an air horn as apposed
to an upwards direction away from the ground below. However so far i am totally
satisfied with the result as is, but will take it further with the internal
baffle and hear what happens
Any technical comments toward the "shut that noise up" project is helpful for Europans..
Read this topic online here:
https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fforums.matronics.com%2Fviewtopic.php%3Fp%3D510467%23510467&data=05%7C01%7C%7Ce88f0b46c7a54be481b708db28033aa4%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C638147766561533529%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=ayTktzrf9sz%2BVN0b1dnDYl0qTVMjz17wy0l1%2BqT%2BPBk%3D&reserved=0
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