Today's Message Index:
----------------------
1. 03:30 AM - Low frequency vibration noise (theo van duin)
2. 06:55 AM - Re: Low frequency vibration noise (Hugh MCKAY III)
3. 07:51 AM - Re: Low frequency vibration noise (Threadcharmer@cs.com)
4. 08:21 AM - Re: Low frequency vibration noise (theo van duin)
5. 09:06 AM - Radio, severe background noise (theo van duin)
6. 11:34 AM - Microair Radio (Threadcharmer@cs.com)
7. 02:34 PM - Re: Low frequency vibration noise (Brad Kramer)
8. 06:52 PM - Re: Radio, severe background noise (Hugh MCKAY III)
9. 06:53 PM - Re: Low frequency vibration noise (Hugh MCKAY III)
Message 1
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| Subject: | Low frequency vibration noise |
Fellow Allegro listers,
When flying my Allegro I regularly do hear a low frequency vibration noise
(about 1 to 2 Hz)
in my headphone, especially during climb. The motor is a Rotax 912 UL. The
prop is a
Woodcomp Klassic 160/31R.
It might not be a motor vibration, but coming from somewhere else. I'm very
curious to
find out from where. Could it be related to an unbalance of my propeller or
an incorrectly
adjusted pitch of the blades?
Thanks for any comment on this,
Theo van Duin, France
Allegro 2000 (71MM)
Message 2
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| Subject: | Re: Low frequency vibration noise |
Theo:
-
When did you first begin to hear this noise? I may be wrong, but at one to
two Hz, I don't think it would be related to an out of balance prop because
the Woodcomp prop blades were balanced at the factory and matched to the h
ub by numbers 1 thru 3. Because of their construction, they have little rot
ational mass relative to the rotating mass of the engine. Therefore they wo
uld have little effect unless one has been damaged, or one is severely out
of pitch. Have you checked the tracking and pitch of your prop? If those tw
o items are correct I would begin to look elsewhere for the-cause, such a
s an electrical problem, but at such a low frequency it is hard to imagine
the problem being electrical. Others on this forum may have some better ide
as.
-
Hugh McKay
Allegro 2000
N661WW
Rotax 912
--- On Tue, 10/27/09, theo van duin <t.j.vanduin@gmail.com> wrote:
From: theo van duin <t.j.vanduin@gmail.com>
Subject: Allegro-List: Low frequency vibration noise
Fellow Allegro listers,
-
When flying my Allegro I-regularly-do hear a low frequency vibration no
ise (about-1 to 2 Hz)
in my headphone, especially during climb. The motor is a Rotax 912 UL. The
prop is a
Woodcomp Klassic 160/31R.-
It might not be a motor vibration, but coming from somewhere else. I'm very
curious to
find out from where. Could it be related to an unbalance of my propeller or
an incorrectly
adjusted pitch of the blades?
-
Thanks for any comment on this,
-
Theo van Duin, France
Allegro 2000 (71MM)-
Message 3
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| Subject: | Re: Low frequency vibration noise |
Theo,
Have a passenger check for vibration in the windshield and/or doors. My
Allegro experiences something similar on takeoff and we found it to be
vibration in the upper corners of the windshield. I also get a small bit of
vibration from the doors. It settles down when we power back. Yes, we hear it even
though we have the headsets on...
Hope this helps,
Amy Hackworth
Allegro amphib N306AD
Hobe Sound, FL
Message 4
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| Subject: | Re: Low frequency vibration noise |
Hugh,
The noise was there from the first time we flew with the plane however
remarkably it did not attrack Andr=E9's
attention, as he told me. Andr=E9 checked the pitch of the blades and these
were found to be O.K.
However, an experienced pilot/instructor told us once that to his opinion
the pitch of the blades was adjusted too coarse. At full power
the tachometer reaches something like 5200 r.p.m.
I don't think that the tracking was checked and honestly I'm not quite sure
what "tracking" exactly means and
how this checking could be done.
About propeller damage: initialy there was none. At one occasion, the engin
e
was started over a gravel path
and after that I found damages on two blades: 3 small holes of the size of
a
match head.
Maybe you are right about the cause of the vibration noise being something
electric. This brings me to the next problem I'ld like to resolve by puttin
g
it on the Allegro list. My radio.
Thank you Hugh for your comments,
Theo van Duin
(France)
Allegro 2000 (71MM
)
2009/10/27, Hugh MCKAY III <hgmckay@bellsouth.net>:
>
> Theo:
>
> When did you first begin to hear this noise? I may be wrong, but at one t
o
> two Hz, I don't think it would be related to an out of balance prop becau
se
> the Woodcomp prop blades were balanced at the factory and matched to the
hub
> by numbers 1 thru 3. Because of their construction, they have little
> rotational mass relative to the rotating mass of the engine. Therefore th
ey
> would have little effect unless one has been damaged, or one is severely
out
> of pitch. Have you checked the tracking and pitch of your prop? If those
two
> items are correct I would begin to look elsewhere for the cause, such as
an
> electrical problem, but at such a low frequency it is hard to imagine the
> problem being electrical. Others on this forum may have some better ideas
.
>
> Hugh McKay
> Allegro 2000
> N661WW
> Rotax 912
>
> --- On *Tue, 10/27/09, theo van duin <t.j.vanduin@gmail.com>* wrote:
>
>
> From: theo van duin <t.j.vanduin@gmail.com>
> Subject: Allegro-List: Low frequency vibration noise
> To: allegro-list@matronics.com
> Date: Tuesday, October 27, 2009, 6:28 AM
>
> Fellow Allegro listers,
>
> When flying my Allegro I regularly do hear a low frequency vibration nois
e
> (about 1 to 2 Hz)
> in my headphone, especially during climb. The motor is a Rotax 912 UL. Th
e
> prop is a
> Woodcomp Klassic 160/31R.
> It might not be a motor vibration, but coming from somewhere else. I'm ve
ry
> curious to
> find out from where. Could it be related to an unbalance of my propeller
or
> an incorrectly
> adjusted pitch of the blades?
>
> Thanks for any comment on this,
>
> Theo van Duin, France
> Allegro 2000 (71MM)
>
> *
>
> rel=nofollow target=_blank>http://www.matronics.com/Navigator?Allegro
-List
> et=_blank>http://forums.matronics.com
> llow target=_blank>http://www.matronics.com/contribution
> *
>
> *
>
===========
===========
===========
===========
> *
>
>
Message 5
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| Subject: | Radio, severe background noise |
Fellow Allegro listers,
My radio is a Microair 760 Transceiver of Australian make. Compared with
what
I do hear through my head set in several other planes I flew with, the
background
noise in my Allegro is much more severe.
Turning the squelch adjustment on the device does not change anything. I
think
I must conclude that the radio is not functioning well and must be repaired.
Did anyone of you experience the same problem with this radio? Any comments?
Theo van Duin, France
Allegro 2000 (71 MM)
Message 6
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My Allegro also uses a Microair 760 and I have been experiencing the same
issue. My headset/com is a Lynx system. I'd also like to hear any ideas you
folks may have.
Amy Hackworth
N306AD
Message 7
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| Subject: | Re: Low frequency vibration noise |
This is a long-shot, but I had some vibration that turned out to be from
the plastic plug coming out of the gearbox shaft. It was inside the spinn
er and apparently that was enough to throw off the balance a bit.
Brad Kramer
N221FA
Bismarck/Mandan ND (Y19)
-----Original Message-----
From: theo van duin [mailto:t.j.vanduin@gmail.com]
Sent: Tuesday, October 27, 2009 05:28 AM
Subject: Allegro-List: Low frequency vibration noise
Fellow Allegro listers,
When flying my Allegro I regularly do hear a low frequency vibration nois
e (about 1 to 2 Hz)
in my headphone, especially during climb. The motor is a Rotax 912 UL. Th
e prop is a
Woodcomp Klassic 160/31R.
It might not be a motor vibration, but coming from somewhere else. I'm ve
ry curious to
find out from where. Could it be related to an unbalance of my propeller
or an incorrectly
adjusted pitch of the blades?
Thanks for any comment on this,
Theo van Duin, France
Allegro 2000 (71MM)
=
Message 8
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| Subject: | Re: Radio, severe background noise |
Theo:
-
Sorry, I am not familier with this radio, so I can't comment specifically.
However, I will say that with any electrical system on-a Rotax 912 engine
, and especially if one has a radio, one needs to have at least a 22,000 mi
cro-farad capacitor in the electrical system to act as a filter for the AC
current noise generated by the rotax engine. You should check, or have some
one knowledgable check to see if your engine has this capacitor in the elec
trical system. If you would like to know where the capacitor is located I c
an fax you a copy of the Rotax 912 electrical diagram and mark where it sho
uld be in the electrical system. Just send me your fax number. If you have
a Rotax 912 Installation Manual dated May 1, 2007 the capacitor is shown as
item 14 on page 109.
-
Hugh
--- On Tue, 10/27/09, theo van duin <t.j.vanduin@gmail.com> wrote:
From: theo van duin <t.j.vanduin@gmail.com>
Subject: Allegro-List: Radio, severe background noise
Fellow Allegro listers,
-
My radio is a Microair 760 Transceiver of Australian make. Compared with wh
at
I do hear through my head set in several other planes I flew with, the back
ground
noise in-my Allegro is much more severe.
-
Turning the squelch adjustment on the device does not change anything. I th
ink
I must conclude that the radio is not functioning well and must be repaired
.
-
Did anyone of you experience the same problem with this radio? Any comments
?
-
Theo van Duin, France
Allegro 2000 (71 MM)---
Message 9
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| Subject: | Re: Low frequency vibration noise |
Theo:
-
Just "Google" the words Propeller Tracking and you will find the first list
ing to be a video of how to track a wooden propeller. The principal is the
same for a three blade prop. It is easy to do. For the 912 UL engine I woul
d suggest you remove one of the plugs from each of the four cylinders to re
lieve the cylinder compression before you track the prop. You can also chec
k with one of your airplane mechanic friends and he can explain tracking fu
rther if you need help.
-
The full take-off power of-your engine (5200 rpm) is somewhat low due to
the coarse pitch of the blades, but acceptable. Rotax's maximum engine take
-off speed is 5800 rpm for no more than 5 minutes, and the maximum continuo
us engine rpm is 5500 rpm. The maximum rpm for-your Woodcomp 3 blade prop
is 2700 rpm. At-your maximum-engine rpm of 5200 rpm, the prop speed is
only 2291 rpm which is well below the maximum allowed by Woodcomp. To incr
ease the maximum take-off speed of your engine you would need to decrease t
he propeller pitch slightly. Unless you have someone who knows how to do th
is, and has done it in the past, I would not attempt it yourself.
-
However, you can check the tracking of the blades, and I would recommend th
at you do so.
-
Hugh
--- On Tue, 10/27/09, theo van duin <t.j.vanduin@gmail.com> wrote:
From: theo van duin <t.j.vanduin@gmail.com>
Subject: Re: Allegro-List: Low frequency vibration noise
Hugh,
-
The noise was there from the first time we flew with the plane however rema
rkably it did not attrack Andr=E9's
attention, as he told me. Andr=E9 checked the pitch of the blades and these
were found to be O.K.
However, an experienced pilot/instructor told us once that to his opinion t
he pitch of the blades was adjusted too coarse. At full power the-tachome
ter reaches something like 5200 r.p.m.
-
I don't think that the tracking was checked and honestly I'm not quite sure
what "tracking" exactly means and
how this checking could be done.
-
About propeller damage: initialy there was none. At one occasion, the engin
e was started over a gravel path
and after that I found damages-on two blades: 3 small holes of the size o
f a match head.-
-
Maybe you are right about the cause of the vibration noise being something
electric. This brings me to the next problem I'ld like to resolve by puttin
g it on the Allegro list. My radio.
-
Thank you Hugh for your comments,
-------------------------
-------------------------
----- Theo van Duin (France)
-------------------------
-------------------------
-------Allegro 2000 (71MM)
-
-
-
2009/10/27, Hugh MCKAY III <hgmckay@bellsouth.net>:
Theo:
-
When did you first begin to hear this noise? I may be wrong, but at one to
two Hz, I don't think it would be related to an out of balance prop because
the Woodcomp prop blades were balanced at the factory and matched to the h
ub by numbers 1 thru 3. Because of their construction, they have little rot
ational mass relative to the rotating mass of the engine. Therefore they wo
uld have little effect unless one has been damaged, or one is severely out
of pitch. Have you checked the tracking and pitch of your prop? If those tw
o items are correct I would begin to look elsewhere for the-cause, such a
s an electrical problem, but at such a low frequency it is hard to imagine
the problem being electrical. Others on this forum may have some better ide
as.
-
Hugh McKay
Allegro 2000
N661WW
Rotax 912
--- On Tue, 10/27/09, theo van duin <t.j.vanduin@gmail.com> wrote:
-
From: theo van duin <t.j.vanduin@gmail.com>
Subject: Allegro-List: Low frequency vibration noise
Fellow Allegro listers,
-
When flying my Allegro I-regularly-do hear a low frequency vibration no
ise (about-1 to 2 Hz)
in my headphone, especially during climb. The motor is a Rotax 912 UL. The
prop is a
Woodcomp Klassic 160/31R.-
It might not be a motor vibration, but coming from somewhere else. I'm very
curious to
find out from where. Could it be related to an unbalance of my propeller or
an incorrectly
adjusted pitch of the blades?
-
Thanks for any comment on this,
-
Theo van Duin, France
Allegro 2000 (71MM)-
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