balancing act

Here's one for the pros: I was balancing my tail rotor and had it down to
0.27 ips and still had just a touch too much weight where I had added it.
So still needing to safety wire a bolt that is located in the center of the
tail rotor output shaft, I chose to safety it to a hole 180 degrees from the
weight. The safety wire was small, 0.025, so I didn't expect to see the ips
go to zero, but I hoped they would decrease maybe to 0.20. Well it didn't.
All of a sudden I had 0.9ips, so I shut down and removed the wire and ran
again. This time I got 0.5 ips. The balancer reading did not even come
close to repeating. The phase angle was also different. In an experiment,
I would run up from idle to full chat and take 4 averaged readings, come
back to idle and go up to full chat again for another 4 readings. Never
repeats. Can't find anything loose in the drive or on the blades. If I
pull a set of readings at 2500, 2600 and 2700, all the readings pretty much
agree with the exception of ips increasing a bit with rpm. However if I
take it to idle and come back up, I get a different set.
Any ideas?
--
Stuart Fields
Experimental Helo magazine
P. O. Box 1585
Inyokern, CA 93527
(760) 377-4478 ph
(760) 408-9747 publication cell

Hi Stuart & Kathryn,

What kind of helicopter are you talking about here?

Please excuse a wild guess from someone who has "very" little experience in
the experimental world but......... since you're not finding anything
overtly loose in the drive system or tail blades, I have to wonder about
something like a bearing going south on you? It might not be anything
you'll feel just moving a static system round but could start causing
problems when under load. Is there any kind of preload put on the system
during assembly? If so, is it even?

As I said, I'm just guessing here so if I'm totally out of line, please
excuse the reply! ;-)

Best of luck & fly safe,
Steve R.


"Stuart & Kathryn Fields" wrote in message
.. .
Here's one for the pros: I was balancing my tail rotor and had it down to
0.27 ips and still had just a touch too much weight where I had added it.
So still needing to safety wire a bolt that is located in the center of
the tail rotor output shaft, I chose to safety it to a hole 180 degrees
from the weight. The safety wire was small, 0.025, so I didn't expect to
see the ips go to zero, but I hoped they would decrease maybe to 0.20.
Well it didn't. All of a sudden I had 0.9ips, so I shut down and removed
the wire and ran again. This time I got 0.5 ips. The balancer reading
did not even come close to repeating. The phase angle was also different.
In an experiment, I would run up from idle to full chat and take 4
averaged readings, come back to idle and go up to full chat again for
another 4 readings. Never repeats. Can't find anything loose in the
drive or on the blades. If I pull a set of readings at 2500, 2600 and
2700, all the readings pretty much agree with the exception of ips
increasing a bit with rpm. However if I take it to idle and come back up,
I get a different set.
Any ideas?
--
Stuart Fields
Experimental Helo magazine
P. O. Box 1585
Inyokern, CA 93527
(760) 377-4478 ph
(760) 408-9747 publication cell

Hello Stu,
Do you clamp the rudder pedals while doing this? Have you checked the tail
rotor tracking before? where do you put the reflecting tape for your DSS or
Prodrive? How many hours do you have?
Claude.
"Steve R" a écrit dans le message de news:
...
Hi Stuart & Kathryn,

What kind of helicopter are you talking about here?

Please excuse a wild guess from someone who has "very" little experience
in the experimental world but......... since you're not finding anything
overtly loose in the drive system or tail blades, I have to wonder about
something like a bearing going south on you? It might not be anything
you'll feel just moving a static system round but could start causing
problems when under load. Is there any kind of preload put on the system
during assembly? If so, is it even?

As I said, I'm just guessing here so if I'm totally out of line, please
excuse the reply! ;-)

Best of luck & fly safe,
Steve R.


"Stuart & Kathryn Fields" wrote in message
.. .
Here's one for the pros: I was balancing my tail rotor and had it down
to 0.27 ips and still had just a touch too much weight where I had added
it. So still needing to safety wire a bolt that is located in the center
of the tail rotor output shaft, I chose to safety it to a hole 180
degrees from the weight. The safety wire was small, 0.025, so I didn't
expect to see the ips go to zero, but I hoped they would decrease maybe
to 0.20. Well it didn't. All of a sudden I had 0.9ips, so I shut down and
removed the wire and ran again. This time I got 0.5 ips. The balancer
reading did not even come close to repeating. The phase angle was also
different. In an experiment, I would run up from idle to full chat and
take 4 averaged readings, come back to idle and go up to full chat again
for another 4 readings. Never repeats. Can't find anything loose in the
drive or on the blades. If I pull a set of readings at 2500, 2600 and
2700, all the readings pretty much agree with the exception of ips
increasing a bit with rpm. However if I take it to idle and come back
up, I get a different set.
Any ideas?
--
Stuart Fields
Experimental Helo magazine
P. O. Box 1585
Inyokern, CA 93527
(760) 377-4478 ph
(760) 408-9747 publication cell

Stu ,
I was just thinking: maybe the problem is comming from your balancer.
"Stuart & Kathryn Fields" a écrit dans le message de news:
...
Here's one for the pros: I was balancing my tail rotor and had it down to
0.27 ips and still had just a touch too much weight where I had added it.
So still needing to safety wire a bolt that is located in the center of
the tail rotor output shaft, I chose to safety it to a hole 180 degrees
from the weight. The safety wire was small, 0.025, so I didn't expect to
see the ips go to zero, but I hoped they would decrease maybe to 0.20.
Well it didn't. All of a sudden I had 0.9ips, so I shut down and removed
the wire and ran again. This time I got 0.5 ips. The balancer reading
did not even come close to repeating. The phase angle was also different.
In an experiment, I would run up from idle to full chat and take 4
averaged readings, come back to idle and go up to full chat again for
another 4 readings. Never repeats. Can't find anything loose in the
drive or on the blades. If I pull a set of readings at 2500, 2600 and
2700, all the readings pretty much agree with the exception of ips
increasing a bit with rpm. However if I take it to idle and come back up,
I get a different set.
Any ideas?
--
Stuart Fields
Experimental Helo magazine
P. O. Box 1585
Inyokern, CA 93527
(760) 377-4478 ph
(760) 408-9747 publication cell

Steve: It is a Baby Belle. I recently repeated with just the engine
driving the main rotor and the tail rotor disconnected. I measured the
vibration at the tail rotor gear box to see if the engine vibration was
coupling thru the tail boom. Nope. I ran the engine up and took readings,
backed it to idle and went up again. Did not get repeatable readings. I
will try the balancer on a D.C. motor and flywheel I've rigged up and see
what it does.
I've been doing an article for our magazine on the comparison between the
Pro-Drive balancer and the DSS Micro Balancer and stumbled onto this
problem. In the past I've balanced mine and two other ships tail rotors
down to the 0.05 ips levels fairly easily. Now with the readings skipping
around, I don't have a chance.
BTW balancing the main rotor at it's 500 rpm does not have this problem. It
repeats nicely.

--
Kathryn Fields
Experimental Helo magazine
P. O. Box 1585
Inyokern, CA 93527
(760) 377-4478 ph
(760) 408-9747 publication cell
"Steve R" wrote in message
...
Hi Stuart & Kathryn,

What kind of helicopter are you talking about here?

Please excuse a wild guess from someone who has "very" little experience
in the experimental world but......... since you're not finding anything
overtly loose in the drive system or tail blades, I have to wonder about
something like a bearing going south on you? It might not be anything
you'll feel just moving a static system round but could start causing
problems when under load. Is there any kind of preload put on the system
during assembly? If so, is it even?

As I said, I'm just guessing here so if I'm totally out of line, please
excuse the reply! ;-)

Best of luck & fly safe,
Steve R.


"Stuart & Kathryn Fields" wrote in message
.. .
Here's one for the pros: I was balancing my tail rotor and had it down
to 0.27 ips and still had just a touch too much weight where I had added
it. So still needing to safety wire a bolt that is located in the center
of the tail rotor output shaft, I chose to safety it to a hole 180
degrees from the weight. The safety wire was small, 0.025, so I didn't
expect to see the ips go to zero, but I hoped they would decrease maybe
to 0.20. Well it didn't. All of a sudden I had 0.9ips, so I shut down and
removed the wire and ran again. This time I got 0.5 ips. The balancer
reading did not even come close to repeating. The phase angle was also
different. In an experiment, I would run up from idle to full chat and
take 4 averaged readings, come back to idle and go up to full chat again
for another 4 readings. Never repeats. Can't find anything loose in the
drive or on the blades. If I pull a set of readings at 2500, 2600 and
2700, all the readings pretty much agree with the exception of ips
increasing a bit with rpm. However if I take it to idle and come back
up, I get a different set.
Any ideas?
--
Stuart Fields
Experimental Helo magazine
P. O. Box 1585
Inyokern, CA 93527
(760) 377-4478 ph
(760) 408-9747 publication cell

Claude Yep clamped pedals and track set up to the nearest 0.1 degree and
checked with eyeball. I'm putting the tape on the blade grip and am using
the DSS. The Pro-Drive did a 180 flip on me and I got mad and took it off
and am using the DSS. I've got 225hrs on the ship and the tail rotor has
about 160. I can't feel any bearing troubles.
Can't see how an out of track blade could cause the ips to increase and the
phase angle to change so much. On the main rotor the out of track generates
vertical vibration and doesn't affect the lateral very much at all.

--
Stuart Fields
Experimental Helo magazine
P. O. Box 1585
Inyokern, CA 93527
(760) 377-4478 ph
(760) 408-9747 publication cell
"claude lescure" wrote in message
...
Hello Stu,
Do you clamp the rudder pedals while doing this? Have you checked the tail
rotor tracking before? where do you put the reflecting tape for your DSS
or Prodrive? How many hours do you have?
Claude.
"Steve R" a écrit dans le message de
news: ...
Hi Stuart & Kathryn,

What kind of helicopter are you talking about here?

Please excuse a wild guess from someone who has "very" little experience
in the experimental world but......... since you're not finding anything
overtly loose in the drive system or tail blades, I have to wonder about
something like a bearing going south on you? It might not be anything
you'll feel just moving a static system round but could start causing
problems when under load. Is there any kind of preload put on the system
during assembly? If so, is it even?

As I said, I'm just guessing here so if I'm totally out of line, please
excuse the reply! ;-)

Best of luck & fly safe,
Steve R.


"Stuart & Kathryn Fields" wrote in message
.. .
Here's one for the pros: I was balancing my tail rotor and had it down
to 0.27 ips and still had just a touch too much weight where I had added
it. So still needing to safety wire a bolt that is located in the center
of the tail rotor output shaft, I chose to safety it to a hole 180
degrees from the weight. The safety wire was small, 0.025, so I didn't
expect to see the ips go to zero, but I hoped they would decrease maybe
to 0.20. Well it didn't. All of a sudden I had 0.9ips, so I shut down
and removed the wire and ran again. This time I got 0.5 ips. The
balancer reading did not even come close to repeating. The phase angle
was also different. In an experiment, I would run up from idle to full
chat and take 4 averaged readings, come back to idle and go up to full
chat again for another 4 readings. Never repeats. Can't find anything
loose in the drive or on the blades. If I pull a set of readings at
2500, 2600 and 2700, all the readings pretty much agree with the
exception of ips increasing a bit with rpm. However if I take it to
idle and come back up, I get a different set.
Any ideas?
--
Stuart Fields
Experimental Helo magazine
P. O. Box 1585
Inyokern, CA 93527
(760) 377-4478 ph
(760) 408-9747 publication cell

claude lescure wrote:

Stu ,
I was just thinking: maybe the problem is comming from your balancer.

Along those lines, Chadwick-Helmuth makes (or used to make) a calibrator
for the purpose of check the balancing equipment. It was a fairly
simple device and probably could be duplicated (as the Chadwick version
was pricey). After chasing the T/R balance on my 269, it turned out the
problem was indeed the CH balancer. It was not an obvous problem.

I looked online and noticed that CH had been purchased by Honeywell and
I wasn't able to find any further info.

Gary

Steve,

It's been a while since I did any aviation maintenance, but the bearing
thing was exactly my thought as she described an unattributed shift in
the ips and phase angles on the repeated runs.

Once upon a time (it was a Sikorsky product) a T/R paddle had debonded
at one end, but internally, and was causing the maintenance pilot fits
as he tried to balance it. He even accused me of putting it back
together incorrectly just prior to my departing for vacation. He was
wrong. When they swapped out the T/R paddle and it balanced out, they
removed the boots from the bad T/R component and found it had failed.
The only symptom that I remember was variable ips readings and changing
phase angles of successive readings.

Linc

Steve R wrote:
Hi Stuart & Kathryn,

What kind of helicopter are you talking about here?

Please excuse a wild guess from someone who has "very" little experience in
the experimental world but......... since you're not finding anything
overtly loose in the drive system or tail blades, I have to wonder about
something like a bearing going south on you? It might not be anything
you'll feel just moving a static system round but could start causing
problems when under load. Is there any kind of preload put on the system
during assembly? If so, is it even?

As I said, I'm just guessing here so if I'm totally out of line, please
excuse the reply! ;-)

Best of luck & fly safe,
Steve R.


"Stuart & Kathryn Fields" wrote in message
.. .
Here's one for the pros: I was balancing my tail rotor and had it down to
0.27 ips and still had just a touch too much weight where I had added it.
So still needing to safety wire a bolt that is located in the center of
the tail rotor output shaft, I chose to safety it to a hole 180 degrees
from the weight. The safety wire was small, 0.025, so I didn't expect to
see the ips go to zero, but I hoped they would decrease maybe to 0.20.
Well it didn't. All of a sudden I had 0.9ips, so I shut down and removed
the wire and ran again. This time I got 0.5 ips. The balancer reading
did not even come close to repeating. The phase angle was also different.
In an experiment, I would run up from idle to full chat and take 4
averaged readings, come back to idle and go up to full chat again for
another 4 readings. Never repeats. Can't find anything loose in the
drive or on the blades. If I pull a set of readings at 2500, 2600 and
2700, all the readings pretty much agree with the exception of ips
increasing a bit with rpm. However if I take it to idle and come back up,
I get a different set.
Any ideas?
--
Stuart Fields
Experimental Helo magazine
P. O. Box 1585
Inyokern, CA 93527
(760) 377-4478 ph
(760) 408-9747 publication cell

Bad blade dampers on articulated (main) heads cause fits too. The test
equipment will say to make such-and-such adjustments, the guys make
those adjustments, you run the test again thinking the numbers will be
in limits or at least closer, and instead the equipment comes back with
numbers that make no sense.

I know the maintenance guys _hate_ changing out a damper.

For the OP, are there accessories running off the shaft? (Oil cooling
fan maybe?) What about the basics, is everything torqued properly,
clean, nothing loose (gearbox oil cap, access panels, so on)?

Linc wrote:
Steve,

It's been a while since I did any aviation maintenance, but the bearing
thing was exactly my thought as she described an unattributed shift in
the ips and phase angles on the repeated runs.

Once upon a time (it was a Sikorsky product) a T/R paddle had debonded
at one end, but internally, and was causing the maintenance pilot fits
as he tried to balance it. He even accused me of putting it back
together incorrectly just prior to my departing for vacation. He was
wrong. When they swapped out the T/R paddle and it balanced out, they
removed the boots from the bad T/R component and found it had failed.
The only symptom that I remember was variable ips readings and changing
phase angles of successive readings.

Linc

Steve R wrote:
Hi Stuart & Kathryn,

What kind of helicopter are you talking about here?

Please excuse a wild guess from someone who has "very" little experience in
the experimental world but......... since you're not finding anything
overtly loose in the drive system or tail blades, I have to wonder about
something like a bearing going south on you? It might not be anything
you'll feel just moving a static system round but could start causing
problems when under load. Is there any kind of preload put on the system
during assembly? If so, is it even?

As I said, I'm just guessing here so if I'm totally out of line, please
excuse the reply! ;-)

Best of luck & fly safe,
Steve R.


"Stuart & Kathryn Fields" wrote in message
.. .
Here's one for the pros: I was balancing my tail rotor and had it down to
0.27 ips and still had just a touch too much weight where I had added it.
So still needing to safety wire a bolt that is located in the center of
the tail rotor output shaft, I chose to safety it to a hole 180 degrees
from the weight. The safety wire was small, 0.025, so I didn't expect to
see the ips go to zero, but I hoped they would decrease maybe to 0.20.
Well it didn't. All of a sudden I had 0.9ips, so I shut down and removed
the wire and ran again. This time I got 0.5 ips. The balancer reading
did not even come close to repeating. The phase angle was also different.
In an experiment, I would run up from idle to full chat and take 4
averaged readings, come back to idle and go up to full chat again for
another 4 readings. Never repeats. Can't find anything loose in the
drive or on the blades. If I pull a set of readings at 2500, 2600 and
2700, all the readings pretty much agree with the exception of ips
increasing a bit with rpm. However if I take it to idle and come back up,
I get a different set.
Any ideas?
--
Stuart Fields
Experimental Helo magazine
P. O. Box 1585
Inyokern, CA 93527
(760) 377-4478 ph
(760) 408-9747 publication cell

Stu,
If I understand, the figures in term of IPS and angle does not repeat each
time you decrease to idle and start again.I may be incorrect but each time
you are passing though idle the engine crankwheel can take a different place
due to freewheel. And the vibrations from engine(same speed than tail rotor)
could mix, interfer or be added and amplified with the tail rotor
assembly.The different place taken by the engine crankwheel and slip between
engine and rotor shaft each time you reduce the throtle could be the
answer for non repeatable reading .
Have you tried to put a velocimeter on the engine itself to see the level of
vibrations at 2700RPM?
Where did you disconnect the tail rotor drive? is it on the mainrotor side
or on the tail rotor side?
First try to check your DSS on a bench.I am almost sure that it is ok as
the figures are constant as you go from 2500 to 2700 except IPS slight
increasing. You could as well make a try with the second velocemeter.
About tracking influence on vibration I can assure that on main rotor
track adjustment has mainly effect on vertical vibration but have as well a
great effect on lateral vibration. And it should be the same on tail rotor.
Last time I balanced my tail rotor I had difficulties to get below 0.2 IPS.
I am sure you will succeed.
Claude
"Gary Knutson" a écrit dans le message de news:
Tv6fg.98088$iU2.89247@fed1read01...


claude lescure wrote:

Stu ,
I was just thinking: maybe the problem is comming from your balancer.

Along those lines, Chadwick-Helmuth makes (or used to make) a calibrator
for the purpose of check the balancing equipment. It was a fairly simple
device and probably could be duplicated (as the Chadwick version was
pricey). After chasing the T/R balance on my 269, it turned out the
problem was indeed the CH balancer. It was not an obvous problem.

I looked online and noticed that CH had been purchased by Honeywell and I
wasn't able to find any further info.

Gary