Here's a challenge for you all:

The flat we live in has a wide balcony surrounded by vertical metal
bars topped by a larger diameter round rail.

The vertical bars are approx. 1cm diameter and 1m long (didn't measure
- guestimated) and spaced about 10 cm from each other. When the wind
blows (which seems to be continuous as we are on the coast) the
vertical bars get into rythm and make quite an impressive noise. so
much so that some of the residents cannot sleep (their balconies are
the same).

Can anyone suggest a method to stop this? We cannot fix them in the
middle with a horizontal bar because of safety regulations. I was
thinking of something like the dampers used on high-voltage lines to
stop the conductors vibrating (see http://tinyurl.com/bobpo for
details).

Is there anywhere on the 'net that can calculate the weight required?

TIA for any help...

On 17 Feb 2006 03:45:37 -0800, "Englishman in Adana (Turkey)"
wrote:

Here's a challenge for you all:

The flat we live in has a wide balcony surrounded by vertical metal
bars topped by a larger diameter round rail.

The vertical bars are approx. 1cm diameter and 1m long (didn't measure
- guestimated) and spaced about 10 cm from each other. When the wind
blows (which seems to be continuous as we are on the coast) the
vertical bars get into rythm and make quite an impressive noise. so
much so that some of the residents cannot sleep (their balconies are
the same).

Can anyone suggest a method to stop this? We cannot fix them in the
middle with a horizontal bar because of safety regulations. I was
thinking of something like the dampers used on high-voltage lines to
stop the conductors vibrating (see http://tinyurl.com/bobpo for
details).

Is there anywhere on the 'net that can calculate the weight required?

TIA for any help...

Can't help with an answer but what safety regs prevent you fitting a
horizontal bar and why should that make them any less safe ..?


Stuart

Englishman in Adana (Turkey) wrote:
The flat we live in has a wide balcony surrounded by vertical metal
bars topped by a larger diameter round rail.

The vertical bars are approx. 1cm diameter and 1m long (didn't measure
- guestimated) and spaced about 10 cm from each other. When the wind
blows (which seems to be continuous as we are on the coast) the
vertical bars get into rythm and make quite an impressive noise. so
much so that some of the residents cannot sleep (their balconies are
the same).

Can anyone suggest a method to stop this? We cannot fix them in the
middle with a horizontal bar because of safety regulations.

Can you clamp a bar to the middle as a "temporary measure", or
use "U" bolts to clamp something vertically onto some of the bars?

Stuart wrote:
On 17 Feb 2006 03:45:37 -0800, "Englishman in Adana (Turkey)"
wrote:

Here's a challenge for you all:

The flat we live in has a wide balcony surrounded by vertical metal
bars topped by a larger diameter round rail.

The vertical bars are approx. 1cm diameter and 1m long (didn't measure
- guestimated) and spaced about 10 cm from each other. When the wind
blows (which seems to be continuous as we are on the coast) the
vertical bars get into rythm and make quite an impressive noise. so
much so that some of the residents cannot sleep (their balconies are
the same).

Can anyone suggest a method to stop this? We cannot fix them in the
middle with a horizontal bar because of safety regulations. I was
thinking of something like the dampers used on high-voltage lines to
stop the conductors vibrating (see http://tinyurl.com/bobpo for
details).

Is there anywhere on the 'net that can calculate the weight required?

TIA for any help...

Can't help with an answer but what safety regs prevent you fitting a
horizontal bar and why should that make them any less safe ..?


Stuart

that was my though, also slapping random weights on them (in the middle)
will at least mean that the overall resonance of ALL of them will be
broken up..

Stuart wrote:
Can't help with an answer but what safety regs prevent you fitting a
horizontal bar and why should that make them any less safe ..?

Presumably it makes it easier for infants to climb them.

Englishman in Adana (Turkey) wrote:
Here's a challenge for you all:

The flat we live in has a wide balcony surrounded by vertical metal
bars topped by a larger diameter round rail.

The vertical bars are approx. 1cm diameter and 1m long (didn't measure
- guestimated) and spaced about 10 cm from each other. When the wind
blows (which seems to be continuous as we are on the coast) the
vertical bars get into rythm and make quite an impressive noise. so
much so that some of the residents cannot sleep (their balconies are
the same).

Can anyone suggest a method to stop this? We cannot fix them in the
middle with a horizontal bar because of safety regulations. I was
thinking of something like the dampers used on high-voltage lines to
stop the conductors vibrating (see http://tinyurl.com/bobpo for
details).

Is there anywhere on the 'net that can calculate the weight required?

TIA for any help...

they might work in a horizontal plane but how do you know they will work in
an Vertical upright plane?

Given the fact we don't know the regulations as to why you can't fit
stabiliser bar in center, can you explain what the regs mean? as to why you
cant do this.

--
Sir Benjamin Middlethwaite

In article ,
Stuart wrote:
Can't help with an answer but what safety regs prevent you fitting a
horizontal bar and why should that make them any less safe ..?

Climbing up and over?

I assume the problem is that the horizontal bar would need to be fixed solid
in order to stop the vertical bars from vibrating at that frequency - and such
a bar would be unsafe. All that's left is to change the profile of the
vertical bars by adding something to them - at the extreme a piece of
panelling along the whole area. Whatever you do you have an aesthetics
problem...

Unless you fix a horizontal bar at some distance *outside* the vertical bars
but attached to each. Expensive and it may not work. ;-(

--
John Cartmell john@ followed by finnybank.com 0845 006 8822
Qercus magazine FAX +44 (0)8700-519-527 www.finnybank.com
Qercus - the best guide to RISC OS computing

Can't help with an answer but what safety regs prevent you fitting a
horizontal bar and why should that make them any less safe ..?


Stuart

Fitting a horizontal bar would make them easier to climb. You know how kids
love to climb stuff.

Grumble

"Englishman in Adana (Turkey)" wrote in message
oups.com...
Here's a challenge for you all:

The flat we live in has a wide balcony surrounded by vertical metal
bars topped by a larger diameter round rail.

The vertical bars are approx. 1cm diameter and 1m long (didn't measure
- guestimated) and spaced about 10 cm from each other. When the wind
blows (which seems to be continuous as we are on the coast) the
vertical bars get into rythm and make quite an impressive noise. so
much so that some of the residents cannot sleep (their balconies are
the same).

Can anyone suggest a method to stop this? We cannot fix them in the
middle with a horizontal bar because of safety regulations. I was
thinking of something like the dampers used on high-voltage lines to
stop the conductors vibrating (see http://tinyurl.com/bobpo for
details).

Is there anywhere on the 'net that can calculate the weight required?

You could grip the vertical bars and or the horisontal bar in different
places (one at a time) to see whether the vibration is damped by contact
with your hand, with this method you might find the antinodes of the
offending vibrating member(s), you might even be able to feel the vibration?
The solution to the problem will probably become obvious to you once you've
established the position of the antinodes, However come back to us with more
info, it's quite an interesting problem
Regards
Donwill

Englishman in Adana (Turkey) wrote:
Here's a challenge for you all:

The flat we live in has a wide balcony surrounded by vertical metal
bars topped by a larger diameter round rail.

The vertical bars are approx. 1cm diameter and 1m long (didn't measure
- guestimated) and spaced about 10 cm from each other. When the wind
blows (which seems to be continuous as we are on the coast) the
vertical bars get into rythm and make quite an impressive noise. so
much so that some of the residents cannot sleep (their balconies are
the same).

Can anyone suggest a method to stop this? We cannot fix them in the
middle with a horizontal bar because of safety regulations. I was
thinking of something like the dampers used on high-voltage lines to
stop the conductors vibrating (see http://tinyurl.com/bobpo for
details).

Is there anywhere on the 'net that can calculate the weight required?

TIA for any help...

Sheet opaque or transparent perspex affixed to the outside of the rails to
act as wind barrier.

--
Sir Benjamin Middlethwaite

Can anyone suggest a method to stop this? We cannot fix them in the
middle with a horizontal bar because of safety regulations. I was
thinking of something like the dampers used on high-voltage lines to
stop the conductors vibrating (see http://tinyurl.com/bobpo for
details).

Ah!, thats what their for then!. Won't be going 'an nicking some eh!....


Perhaps some plastic polythene clear tubing split down the side then put
over them might damp them without looking a pigs ear?...

Is there anywhere on the 'net that can calculate the weight required?

TIA for any help...


--
Tony Sayer

On Fri, 17 Feb 2006 11:54:56 +0000, Chris Bacon
wrote:

|Englishman in Adana (Turkey) wrote:
| The flat we live in has a wide balcony surrounded by vertical metal
| bars topped by a larger diameter round rail.

In the UK it would make the rails "not fit for purpose"

| The vertical bars are approx. 1cm diameter and 1m long (didn't measure
| - guestimated) and spaced about 10 cm from each other. When the wind
| blows (which seems to be continuous as we are on the coast) the
| vertical bars get into rythm and make quite an impressive noise. so
| much so that some of the residents cannot sleep (their balconies are
| the same).
|
| Can anyone suggest a method to stop this? We cannot fix them in the
| middle with a horizontal bar because of safety regulations.
|
|Can you clamp a bar to the middle as a "temporary measure", or
|use "U" bolts to clamp something vertically onto some of the bars?

This is called resonance, which is quite a problem to get rid of.
Do not put things in the middle, that would merely double the frequency,
1/3 of the way down would triple the frequency. Put things in a position
which does not involve the numbers 1 to 10.

Have you thought of bungee cord which would be cheap and might damp the
resonance.
--
Dave Fawthrop dave hyphenologist co uk
Freedom of Speech, Expression, Religion, and Democracy are
the keys to Civilization, together with legal acceptance of
Fundamental Human rights.

On Fri, 17 Feb 2006 12:07:56 +0000, The Natural Philosopher
wrote:

that was my though, also slapping random weights on them (in the middle)
will at least mean that the overall resonance of ALL of them will be
broken up..

It's possible the bars aren't resonating but the noise is due to the
wind blowing between the bars.

Presumably, if the wind blows at a certain angle you'd get a similar
effect to the hole in an organ pipe?

sponix

Englishman in Adana (Turkey) wrote:


Can anyone suggest a method to stop this? We cannot fix them in the
middle with a horizontal bar because of safety regulations. I was
thinking of something like the dampers used on high-voltage lines to
stop the conductors vibrating (see http://tinyurl.com/bobpo for
details).

Is there anywhere on the 'net that can calculate the weight required?

TIA for any help...

Firstly, although I don't know how to crunch the numbers, I'm sure a
metal bar 1 cm in diameter will be too 'stiff' to vibrate at audio
frequencies, if just driven by air blowing over them at right angles.

What might be happening is that the bars are very slightly different,
and athough resonating inaudibly, the slight differences in frequency
cause a 'beating' or 'heterodyning' to give an audible note.

Another prospect is that the bars are acting as open-ended organ
pipes; these would almost certainly resonate at audio frequencies. The
solution is simple: stop the airflow over the openings.

It might be helpful to describe the kind of sound they make in more
detail; do they do this with *any* wind, or one that blows from a
particular direction? Is there a critical wind-speed?

On Fri, 17 Feb 2006 12:12:46 +0000, Chris Bacon
wrote:

Stuart wrote:
Can't help with an answer but what safety regs prevent you fitting a
horizontal bar and why should that make them any less safe ..?

Presumably it makes it easier for infants to climb them.


Ah right ..Kids ...Grrrr ...Forgot about them pesky critturs ..lol


How about a vertical plate projecting outwards slightly ,one at each
end .Would that possibly work by breaking up the wind blowing through
the bars .Suppose it would depend on the direction of the wind .




Stuart

On Fri, 17 Feb 2006 12:44:46 +0000, Kate wrote:

Another prospect is that the bars are acting as open-ended organ
pipes; these would almost certainly resonate at audio frequencies. The
solution is simple: stop the airflow over the openings.

If, as I suspect the rails are acting as organ pipes, I wonder if
sticking something to the outside of some/all the bars would be
sufficient to break up the airflow?

Self adhesive draught excluder perhaps?

sponix

On Fri, 17 Feb 2006 13:32:43 GMT, (Sponix) wrote:

On Fri, 17 Feb 2006 12:44:46 +0000, Kate wrote:

Another prospect is that the bars are acting as open-ended organ
pipes; these would almost certainly resonate at audio frequencies. The
solution is simple: stop the airflow over the openings.

If, as I suspect the rails are acting as organ pipes, I wonder if
sticking something to the outside of some/all the bars would be
sufficient to break up the airflow?

Self adhesive draught excluder perhaps?

How about growing a climbing plant up the bars?

On Fri, 17 Feb 2006 12:43:13 GMT, (Sponix) wrote:

|On Fri, 17 Feb 2006 12:07:56 +0000, The Natural Philosopher
|wrote:
|
|that was my though, also slapping random weights on them (in the middle)
|will at least mean that the overall resonance of ALL of them will be
|broken up..
|
|It's possible the bars aren't resonating but the noise is due to the
|wind blowing between the bars.

The wind *causes* them to resonate.


--
Dave Fawthrop dave hyphenologist co uk
Freedom of Speech, Expression, Religion, and Democracy are
the keys to Civilization, together with legal acceptance of
Fundamental Human rights.

On Fri, 17 Feb 2006 12:44:46 +0000, Kate wrote:

|
|Englishman in Adana (Turkey) wrote:
|
|
|Can anyone suggest a method to stop this? We cannot fix them in the
|middle with a horizontal bar because of safety regulations. I was
|thinking of something like the dampers used on high-voltage lines to
|stop the conductors vibrating (see http://tinyurl.com/bobpo for
|details).
|
|Is there anywhere on the 'net that can calculate the weight required?
|
|TIA for any help...
|
|Firstly, although I don't know how to crunch the numbers, I'm sure a
|metal bar 1 cm in diameter will be too 'stiff' to vibrate at audio
|frequencies, if just driven by air blowing over them at right angles.

OP does not say they are *solid* metal, Tubes would resonate.

--
Dave Fawthrop dave hyphenologist co uk
Freedom of Speech, Expression, Religion, and Democracy are
the keys to Civilization, together with legal acceptance of
Fundamental Human rights.

Many thanks for all the replies, (I was AMAZED to get 17 replies in 2
hours!!)

Just to sum up the answers:

Yes, the regulations are to prevent climbing and possible falls. There
were horizontal bars there before, they got them all changed at God
knows how much expense!!

The wind doesn't have to be very strong to start the vibration, I guess
the frequency is around 40-60Hz (compared to mains hum on a radio). I
tried holding the bars sometimes, but holding the one making a noise
makes another start!! and it's difficult to determine which is the
culprit. (I thought that the welding may be vibrating but they all seem
firm, therefore resonance is the problem.)

Thought about a bungee cord or similar, plants would be a good solution
but not instant. Methinks trying slit PVC pipe would be easiest, maybe
on just a few of them would solve it...

I'll let you all know after a few attempts. Thanks again

"Sponix" wrote in message
...
On Fri, 17 Feb 2006 12:44:46 +0000, Kate wrote:

Another prospect is that the bars are acting as open-ended organ
pipes; these would almost certainly resonate at audio frequencies. The
solution is simple: stop the airflow over the openings.

If, as I suspect the rails are acting as organ pipes, I wonder if
sticking something to the outside of some/all the bars would be
sufficient to break up the airflow?

Self adhesive draught excluder perhaps?

Pipe insulation on the bars?

Try wrapping some thick cable or hosepipe around each bar in a helix -
something like one turn around the bar for each 10-15cm of length.
This should disrupt the vortex formation which may be driving the
resonance.

John

On 17 Feb 2006 06:09:15 -0800, "Englishman in Adana (Turkey)"
wrote:

I'll let you all know after a few attempts. Thanks again

Once you find a soloution you can sell it to your neighbours!



sponix

Englishman in Adana (Turkey) wrote:

The wind doesn't have to be very strong to start the vibration, I guess
the frequency is around 40-60Hz (compared to mains hum on a radio).

Speed of sound in air is circa 1100 fps, so at 50 Hz) the wavelength
is 22 ft.

Is there *any* dimension on the bars that is near *any* fraction of
22, that is 22, 11, 5.5, 2.75 ft? I'm thinking possibly of the
horizontal bar that tops the smaller, vertical ones, being the
culprit?

I tried holding the bars sometimes, but holding the one making a noise
makes another start!! and it's difficult to determine which is the
culprit.

I'm beginning to think that the vertical bars might not have much to
do with it. The long, horizontal bar seems much more like the culprit.
Are the ends sealed with no air access whatsoever?

Kate wrote:
Englishman in Adana (Turkey) wrote:

The wind doesn't have to be very strong to start the vibration, I
guess the frequency is around 40-60Hz (compared to mains hum on a
radio).

Speed of sound in air is circa 1100 fps, so at 50 Hz) the wavelength
is 22 ft.

Is there *any* dimension on the bars that is near *any* fraction of
22, that is 22, 11, 5.5, 2.75 ft? I'm thinking possibly of the
horizontal bar that tops the smaller, vertical ones, being the
culprit?

I tried holding the bars sometimes, but holding the one making a
noise makes another start!! and it's difficult to determine which is
the culprit.

I'm beginning to think that the vertical bars might not have much to
do with it. The long, horizontal bar seems much more like the culprit.
Are the ends sealed with no air access whatsoever?

Is you're life complicated?

p.s whats "fps"?

--
Sir Benjamin Middlethwaite

On Fri, 17 Feb 2006 15:35:30 +0000, Kate wrote:

|
|Englishman in Adana (Turkey) wrote:
|
|The wind doesn't have to be very strong to start the vibration, I guess
|the frequency is around 40-60Hz (compared to mains hum on a radio).
|
|Speed of sound in air is circa 1100 fps, so at 50 Hz) the wavelength
|is 22 ft.
|
|Is there *any* dimension on the bars that is near *any* fraction of
|22, that is 22, 11, 5.5, 2.75 ft? I'm thinking possibly of the
|horizontal bar that tops the smaller, vertical ones, being the
|culprit?
|
|I tried holding the bars sometimes, but holding the one making a noise
|makes another start!! and it's difficult to determine which is the
|culprit.
|
|I'm beginning to think that the vertical bars might not have much to
|do with it. The long, horizontal bar seems much more like the culprit.
|Are the ends sealed with no air access whatsoever?

Sealing tubes with building sealant would be cheap.
--
Dave Fawthrop dave hyphenologist co uk
Freedom of Speech, Expression, Religion, and Democracy are
the keys to Civilization, together with legal acceptance of
Fundamental Human rights.

"The3rd Earl Of Derby" wrote in message
k...
Kate wrote:
Englishman in Adana (Turkey) wrote:

The wind doesn't have to be very strong to start the vibration, I
guess the frequency is around 40-60Hz (compared to mains hum on a
radio).

Speed of sound in air is circa 1100 fps, so at 50 Hz) the wavelength
is 22 ft.

Is there *any* dimension on the bars that is near *any* fraction of
22, that is 22, 11, 5.5, 2.75 ft? I'm thinking possibly of the
horizontal bar that tops the smaller, vertical ones, being the
culprit?

I tried holding the bars sometimes, but holding the one making a
noise makes another start!! and it's difficult to determine which is
the culprit.

I'm beginning to think that the vertical bars might not have much to
do with it. The long, horizontal bar seems much more like the culprit.
Are the ends sealed with no air access whatsoever?

Is you're life complicated?
What has that got to do with it? she is doing a damn good job of solving the
prob.
p.s whats "fps"?
Come on Benjamin, where have you been?
fps = feet per second
Donwill

On Fri, 17 Feb 2006 15:35:30 +0000, Kate wrote:

I'm beginning to think that the vertical bars might not have much to
do with it. The long, horizontal bar seems much more like the culprit.
Are the ends sealed with no air access whatsoever?

Possibly the bars are hollow tubes with open ends. The wind blowing
across the tops would be like blowing across the tops of empty milk
bottles.

Check the ends of the bars, block them off if they are hollow and see
what happens.

sponix

Donwill wrote:
"The3rd Earl Of Derby" wrote in message
k...
Kate wrote:
Englishman in Adana (Turkey) wrote:

The wind doesn't have to be very strong to start the vibration, I
guess the frequency is around 40-60Hz (compared to mains hum on a
radio).

Speed of sound in air is circa 1100 fps, so at 50 Hz) the wavelength
is 22 ft.

Is there *any* dimension on the bars that is near *any* fraction of
22, that is 22, 11, 5.5, 2.75 ft? I'm thinking possibly of the
horizontal bar that tops the smaller, vertical ones, being the
culprit?

I tried holding the bars sometimes, but holding the one making a
noise makes another start!! and it's difficult to determine which
is the culprit.

I'm beginning to think that the vertical bars might not have much to
do with it. The long, horizontal bar seems much more like the
culprit. Are the ends sealed with no air access whatsoever?

Is you're life complicated?
What has that got to do with it? she is doing a damn good job of
solving the prob.
p.s whats "fps"?
Come on Benjamin, where have you been?
fps = feet per second
Donwill

Its all very well working out the speed of sound and distance measurement,
but he needs a practical solution to stop the resonating.

A bit like an mathematician who complained of having constipation.
Someone said he should work it out with a pencil.

--
Sir Benjamin Middlethwaite

"The3rd Earl Of Derby" wrote in message
k...
Donwill wrote:
"The3rd Earl Of Derby" wrote in message
k...
Kate wrote:
Englishman in Adana (Turkey) wrote:

The wind doesn't have to be very strong to start the vibration, I
guess the frequency is around 40-60Hz (compared to mains hum on a
radio).

Speed of sound in air is circa 1100 fps, so at 50 Hz) the wavelength
is 22 ft.

Is there *any* dimension on the bars that is near *any* fraction of
22, that is 22, 11, 5.5, 2.75 ft? I'm thinking possibly of the
horizontal bar that tops the smaller, vertical ones, being the
culprit?

I tried holding the bars sometimes, but holding the one making a
noise makes another start!! and it's difficult to determine which
is the culprit.

I'm beginning to think that the vertical bars might not have much to
do with it. The long, horizontal bar seems much more like the
culprit. Are the ends sealed with no air access whatsoever?

Is you're life complicated?
What has that got to do with it? she is doing a damn good job of
solving the prob.
p.s whats "fps"?
Come on Benjamin, where have you been?
fps = feet per second
Donwill

Its all very well working out the speed of sound and distance measurement,
but he needs a practical solution to stop the resonating.

A real engineer tries to understand the problem before applying his/her
mind to producing a solution.

A bit like an mathematician who complained of having constipation.
Someone said he should work it out with a pencil.

I suppose it's easier than using a computer even in these days of
minaturisation. Roll on Nano engineering you can get rid of your pencil then
Benjamin.

Regards
Donwill

On Fri, 17 Feb 2006 16:04:26 GMT, (Sponix) wrote:

On Fri, 17 Feb 2006 15:35:30 +0000, Kate wrote:

I'm beginning to think that the vertical bars might not have much to
do with it. The long, horizontal bar seems much more like the culprit.
Are the ends sealed with no air access whatsoever?

Possibly the bars are hollow tubes with open ends. The wind blowing
across the tops would be like blowing across the tops of empty milk
bottles.

Check the ends of the bars, block them off if they are hollow and see
what happens.

sponix

And if it is the bars themselves resonating as opposed to acting like organ pipes, and they are
hollow, filling them with sand ought to damp vibration sufficiently as it will absorb the vibration
energy.

Donwill wrote:
"The3rd Earl Of Derby" wrote in message
k...
Donwill wrote:
"The3rd Earl Of Derby" wrote in message
k...
Kate wrote:
Englishman in Adana (Turkey) wrote:

The wind doesn't have to be very strong to start the vibration, I
guess the frequency is around 40-60Hz (compared to mains hum on a
radio).

Speed of sound in air is circa 1100 fps, so at 50 Hz) the
wavelength is 22 ft.

Is there *any* dimension on the bars that is near *any* fraction
of 22, that is 22, 11, 5.5, 2.75 ft? I'm thinking possibly of the
horizontal bar that tops the smaller, vertical ones, being the
culprit?

I tried holding the bars sometimes, but holding the one making a
noise makes another start!! and it's difficult to determine which
is the culprit.

I'm beginning to think that the vertical bars might not have much
to do with it. The long, horizontal bar seems much more like the
culprit. Are the ends sealed with no air access whatsoever?

Is you're life complicated?
What has that got to do with it? she is doing a damn good job of
solving the prob.
p.s whats "fps"?
Come on Benjamin, where have you been?
fps = feet per second
Donwill

Its all very well working out the speed of sound and distance
measurement, but he needs a practical solution to stop the
resonating.

A real engineer tries to understand the problem before applying
his/her mind to producing a solution.

A bit like an mathematician who complained of having constipation.
Someone said he should work it out with a pencil.

I suppose it's easier than using a computer even in these days of
minaturisation. Roll on Nano engineering you can get rid of your
pencil then Benjamin.

Regards
Donwill

Ok, lets look at this way.

Say she spends half hour working out where the bars are resonating and
comes to the conclusion they are resonating towards the middle, great! we
are back to square one we cant put stabilisers in the middle because of
safety reasons so now we have to work out a solution to stop it bearing in
mind this is all costing money to the poor bloke who's hired an engineer.

Practicability comes before Theory in my book.

--
Sir Benjamin Middlethwaite

Englishman in Adana (Turkey) wrote:
Here's a challenge for you all:


Perhaps a picture of the situation in this problem is called for, so we can
all actaully get a better idea of coming up with a solution.
--
Sir Benjamin Middlethwaite

wrote:
Try wrapping some thick cable or hosepipe around each bar in a helix -
something like one turn around the bar for each 10-15cm of length.
This should disrupt the vortex formation which may be driving the
resonance.


this is probably the best solution. Metal chimney flues on factories
nearly all have a spiral blade running up them at 45 deg. or so to
prevent wind induced vibration

Google for "spiral chimney wind spoiler"


john2

Ok heres for another update:

The vertical bars are, I guess, tubes made of stainless. They are
enclosed at the bottom in a rectangular section and the top disappears
into the horizontal bar. Therefore the ends are not open, either to
cause 'organ pipe' resonance, or to put sand in (which is an idea I
liked).

Maybe I can drill holes at various spacings down the tubes and cause
them to play a nice melody with the wind!!

The idea about wrapping a wire or tube around in a spiral sounds good,
this is also used on electric transmission lines -
http://tinyurl.com/anqaq

Once again, thanks for all the answers! Now for an interesting weekends
work

PS: after asking this question, arriving home in the evening to find no
wind and complete silence amazed me. First time the wind ceased in 2
months!! This group is REALLY effective!! lol

"The3rd Earl Of Derby" wrote in message
k...
Kate wrote:
Englishman in Adana (Turkey) wrote:

The wind doesn't have to be very strong to start the vibration, I
guess the frequency is around 40-60Hz (compared to mains hum on a
radio).

Speed of sound in air is circa 1100 fps, so at 50 Hz) the wavelength
is 22 ft.

Is there *any* dimension on the bars that is near *any* fraction of
22, that is 22, 11, 5.5, 2.75 ft? I'm thinking possibly of the
horizontal bar that tops the smaller, vertical ones, being the
culprit?

I tried holding the bars sometimes, but holding the one making a
noise makes another start!! and it's difficult to determine which is
the culprit.

I'm beginning to think that the vertical bars might not have much to
do with it. The long, horizontal bar seems much more like the culprit.
Are the ends sealed with no air access whatsoever?

Is you're life complicated?

p.s whats "fps"?

--
Sir Benjamin Middlethwaite

Try a coat of DX grease, and tell the world .LOL

Practicability comes before Theory in my book.
Each to his own.
Cheers
Don

Stuart wrote:
On Fri, 17 Feb 2006 12:12:46 +0000, Chris Bacon
wrote:

Stuart wrote:
Can't help with an answer but what safety regs prevent you fitting a
horizontal bar and why should that make them any less safe ..?

Presumably it makes it easier for infants to climb them.

Ah right ..Kids ...Grrrr ...Forgot about them pesky critturs ..lol

How about a vertical plate projecting outwards slightly, one at each end

Horizontal bar with inward facing spikes ?

P.

Dave Fawthrop wrote:
Chris Bacon wrote:
|Englishman in Adana (Turkey) wrote:
| The flat we live in has a wide balcony surrounded by vertical metal
| bars topped by a larger diameter round rail.

| The vertical bars are approx. 1cm diameter and 1m long (didn't measure
| - guestimated) and spaced about 10 cm from each other. When the wind
| blows (which seems to be continuous as we are on the coast) the
| vertical bars get into rythm and make quite an impressive noise.

| Can anyone suggest a method to stop this?

This is called resonance, which is quite a problem to get rid of.

The power line people solved this easily ages ago, with the dampers
shown on the left of here :

http://www.power-technology.com/cont...sco/image2.jpg

Can't you make a suspended weight to a similar design ?

Do not put things in the middle, that would merely double the frequency,
1/3 of the way down would triple the frequency.

Hmm. This would change the pitch granted, but they would be better
supported, lessening the possibility of resonance.

Cheers

Paul.

john2 wrote:

wrote:
Try wrapping some thick cable or hosepipe around each bar in a helix -
something like one turn around the bar for each 10-15cm of length.
This should disrupt the vortex formation which may be driving the
resonance.


this is probably the best solution. Metal chimney flues on factories
nearly all have a spiral blade running up them at 45 deg. or so to
prevent wind induced vibration

Google for "spiral chimney wind spoiler"

----------

This reply should be ignored by "Sir Benjamin Middlethwaite" on the
grounds that it is technically oriented, and his sensibilities in that
area seem very delicate.

---------

Well, I did the Google search, thanks for the steer. I came across
this web site:

http://ew2005.osha.eu.int/europeanno...ew05_veits.pdf

The cause and a couple of remedies are shown in Figure 2, although
there are doubtless many other ways of making a spoiler: a spiral wrap
of thick string or plastic tube, for example.

Let us know how things work out.