# swaying lights



## g-alberta

I have some 1X4 lights hanging from aircraft cable. no HVAC grills or diffusers nearby. I have one row of lights that swing like crazy. some weird convectional currents. Any easy solutions. I was thinking 3/8" reddi-rod but these lights are swinging like crazy. I think they would still swing on rod. the lights are suspended by about 12' of cable so 45 degree ties would look silly.


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## mitch65

Can you raise or lower them to avoid the wind? Sleeve the cable with 10' of pipe (or enough to get below the air currents) with a flange fitting to bolt to the ceiling.


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## just the cowboy

*Don't need to be 45 degrees*

You don't need to be out 45 degrees with extra cables. Try just running a second pair of cables about 2 foot out from the support cables. That way when the breeze blows one way the outside guide cable stops it same as other side.


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## MikeFL

Can you post a video clip?


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## HackWork

What about putting weight on top of or inside of the light?


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## macmikeman

How about informing the customer there is a design flaw with them choosing to put hanging lights in an area that has a wind tunnel, and let them or the designer sort it out. Otherwise , 1/2'' rigid stems. Either way, $$.


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## macmikeman

This leads me to my next rant. We make the lights come on. It is up to the building designers to properly pick the type of lighting for the application. I don't let customers try to put that responsibility on me, unless it is a simple overlooked dark area needs some light problem , and another fluorescent or a pull chain or a recess can ...........


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## HackWork

Maybe the customer asked him to do it and he wants the work and to show the customer that he can take care of issues for them?

I am thinking that lead sheets, like what is used in lead-lined walls in hospitals, would be great to lay on the top of the lights in a few layers. The weight will dampen the swinging quite a bit and possibly stop it altogether.


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## wildleg

HackWork said:


> Maybe the customer asked him to do it and he wants the work and to show the customer that he can take care of issues for them?
> 
> I am thinking that lead sheets, like what is used in lead-lined walls in hospitals, would be great to lay on the top of the lights in a few layers. The weight will dampen the swinging quite a bit and possibly stop it altogether. Also, when it lands on their head, they will forget all about the swaying.


fixed it for ya


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## HackWork

wildleg said:


> fixed it for ya


Can you stop be ******ed for a minute please.


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## wildleg

HackWork said:


> Can you stop be ******ed for a minute please.


now what fun would that be ?


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## MikeFL

I think they stopped making that lead lined sheetrock. Some EPA garbage.

But the adding weight is a great idea.


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## HackWork

MikeFL said:


> I think they stopped making that lead lined sheetrock. Some EPA garbage.
> 
> But the adding weight is a great idea.


I don't doubt it. It's been 10 years since I worked with it. I remember getting sheets of the lead and having to fold it over every fastener I put in the wall.


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## telsa

You're dealing with 'resonance.'

Google it.

To take the cables 'out of tune' -- use split bolt connectors -- try part way up. Just clamp them around the cables -- there being nothing to connect to, of course.

They don't have to be particularly massive, either.

Even one split-bolt connector should ruin// shift the resonance frequency.

The nice thing is that this fix is reversible and pretty cheap... and uses stuff we touch all the time.

Come back and thank me later.


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## wcord

telsa said:


> You're dealing with 'resonance.'
> 
> Google it.
> 
> To take the cables 'out of tune' -- use split bolt connectors -- try part way up. Just clamp them around the cables -- there being nothing to connect to, of course.
> 
> They don't have to be particularly massive, either.
> 
> Even one split-bolt connector should ruin// shift the resonance frequency.
> 
> The nice thing is that this fix is reversible and pretty cheap... and uses stuff we touch all the time.
> 
> Come back and thank me later.



Resonance my butt.

At 12 ft of cable, it doesn't take much air flow to cause the fixtures to sway.
Try to figure out which vent is causing the disturbance, and see if you can either damper down or divert the air flow.


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## MechanicalDVR

Maybe an exorcist if nothing else works!


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## sbrn33

I like haXer but that is a stupid assesd idea. Use a bit heavier chain or cross brace them from an angle. 
The aircraft cable was a mistake so now just go fix it.


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## telsa

wcord said:


> Resonance my butt.
> 
> At 12 ft of cable, it doesn't take much air flow to cause the fixtures to sway.
> Try to figure out which vent is causing the disturbance, and see if you can either damper down or divert the air flow.


Chill down - and spend a year in college level physics.

That's where this matter is beaten to death... and I _mean_ beaten to death.

If air blast was causing this it's still not enough... not enough to be spotted -- so we're not talking an air vent -- rather it's so mild it's a puzzle.


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## wcord

g-alberta said:


> I have some 1X4 lights hanging from aircraft cable. no HVAC grills or diffusers nearby. I have one row of lights that swing like crazy. some weird convectional currents. Any easy solutions. I was thinking 3/8" reddi-rod but these lights are swinging like crazy. I think they would still swing on rod. the lights are suspended by about 12' of cable so 45 degree ties would look silly.





telsa said:


> Chill down - and spend a year in college level physics.
> 
> That's where this matter is beaten to death... and I _mean_ beaten to death.
> 
> If air blast was causing this it's still not enough... not enough to be spotted -- so we're not talking an air vent -- rather it's so mild it's a puzzle.


Read his post. Swinging fixtures , not small vibrations

Resonance: a vibration of large amplitude in a mechanical or electrical system caused by a relatively small periodic stimulus of the same or nearly the same period as the natural vibration period of the system 

Since you cant dazzle us with brilliance, you try to baffle us with BS


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## Big John

Hell, try the weight idea: Just zip-tie a piece of unistrut to the top of the light and see if that does the trick. If it does, bolt it in.

Otherewise, how far apart are the rows? Is it possible to reach the next stationary row with a piece of all-thread where a horizontal rod at each end might be enough to keep it all from moving.


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## splatz

This would be resonance, kind of like jumping on a trampoline






I can't picture it affecting only one row of lights but I guess I couldn't rule it out. Hang a little caution tape on the corners of the lights and you'll get a clue about what the air currents are doing. I guess the air could be pulsing and make a resonant effect...


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## MikeFL

A steady stream of air movement caused by a AHU would tend to hold the fixture(s) slightly offset of directly under their support cables. 

The airstream would have to oscillate to create the swinging motion.

Regardless, more mass will dampen the movement caused by whatever force is acting upon it.

A video clip would be nice.


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## telsa

MikeFL said:


> A steady stream of air movement caused by a AHU would tend to hold the fixture(s) slightly offset of directly under their support cables.
> 
> The airstream would have to oscillate to create the swinging motion.
> 
> Regardless, more mass will dampen the movement caused by whatever force is acting upon it.
> 
> A video clip would be nice.


This is especially true when the mass is attached in the middle -- somewhere -- of the stretched material. ( The wire is in tension, of course. )

This is the actual technique used to un-tune suspension bridges. :thumbsup:

Yes, I was not guessing. :no:


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