149 replies to this topic

[Wallowa]

Wallowa,

I used the CLD tiles on the inner ceiling of my 1993 Pickup cab.  It used to oil can a bit.  It does not do so any longer.   

I am pretty familiar with how metal bends and resonates as well as with vibration testing airborne and spaceborne assemblies but I am not an expert in sound damping. However, there are folks out there that are.  

 

 

 

Thanks for that....resonating/vibrating produces sound, of course in varying frequencies and amplitudes...cause of that movement and how to stop or greatly lessen that movement is the crux for dealing with our TC in FWCs.  If tops sheet only "quivered" the sound might be a hum, but the rapid and significant displacement of the top sheet vertically produces very loud bongs/pops/rounds-going-off sound.

[rubberlegs]

Wallowa,

I used the CLD tiles on the inner ceiling of my 1993 Pickup cab.  It used to oil can a bit.  It does not do so any longer.   

I am pretty familiar with how metal bends and resonates as well as with vibration testing airborne and spaceborne assemblies but I am not an expert in sound damping. However, there are folks out there that are.  

 

 

Interesting. I also worked with aerospace structures, and we had to check for natural frequency -- I think over 33 Hz but my memory is fuzzy. We didn't want our wings resonating, that might frighten passengers, not to mention the pilots and the FAA. It would seem a flat sheet with boundary conditions at the camper framing could be calculated without fancy finite element modeling... but our roof is ok and I'm too lazy!

Edited by rubberlegs, 07 June 2023 - 12:34 AM.

[pvstoy]

Thinking in a different direction.... roll on some camper roof coat between the rails, could add weight and sound dampenor.

[Wallowa]

Time will tell if anyone actually lessens or eliminates tin canning on a FWC that is as bad as on my Hawk....roof coating would have to be damn thick to hold down the top sheet from fluctuating/bouncing up and down in a wind...and 'sound proofing' will only come when the movement of the slack areas in the top sheet is stopped...not by sound absorbing material unless it is rigid and can hold the top sheet still and stop the movement...or by piling on weight in the slack areas....

 

Structural analysis and modeling would be 'nice' but stopping the existing movement, not theoretical movement, real significant popping up and down, is paramount in stopping the TC noise....sure knowing the dynamics and causal factors which may define the issue would be great....but we need to eliminate the "effect" and stop the noise first....not the norm in science, but empirical solutions are what are needed...too late for design changes or thickness changes in existing top sheets...

Edited by Wallowa, 07 June 2023 - 03:01 AM.

[JaSAn]

Structural analysis and modeling would be 'nice' but stopping the existing movement, not theoretical movement, real significant popping up and down, is paramount in stopping the TC noise....sure knowing the dynamics and causal factors which may define the issue would be great....but we need to eliminate the "effect" and stop the noise first....not the norm in science, but empirical solutions are what are needed...too late for design changes or thickness changes in existing top sheets...

Theory is not the end all/be all of a solution but the first step.  It should identify what possible solutions will not work well and what solutions are worth exploring.  Testing still needs to be done.

Seat of the pants trial and error can deliver a solution but it is usually inferior and at higher cost.

 

My recommendation is still to first talk to application engineers that deal with these problems.

 

P.S:  I was a shock and vibration engineer for Control Data and 3M for 37 years, retired for 12.

[Wallowa]

Jasan,

 

While I concur that seat of the pants solutions are truly a hit or miss proposition, as of yet I do not believe anyone has identified an application engineer that deals with this specific FWC problem....I do not discount the value of a methodical engineering analysis and testing protocol, but who will do it and when? 

 

In the mean time the booming of the top piece continues...mine may be a haphazard approach but lessening or stopping the tin canning noise seemingly inherent in the FWC single sheet aluminum top sheet on my Hawk requires actions within my life time and like it or not determining what that action should be falls to me to figure out....all this assumes that there is indeed a feasible retro fix and not just to start over with a thicker top sheet and with designed in stiffening ribs as seen on metal roofs....Google "tin canning"; volumes on this as it is common with metal sheets used on buildings; seemly thicker material and with designed in stiffeners partially stops or at least lessens the tin canning. Cosmetic reduction in buildings of TC is not my objective, but elimination or reducing of the popping or booming sound is.

 

Phil

Edited by Wallowa, 08 June 2023 - 03:17 AM.

[Jon R]

Oil canning is the term used for this in the engineering world (referring to the intended popping characteristic of the bottom of an old-school oil can). A search on tin canning will yield results on food storage.

[Wallowa]

Jon,

 

You are correct...no idea where I got stuck on "tin" rather than "oil canning"....my error...never intended to can food in the Hawk! 

 

https://roofonline.c...’s oil canning.

 

Ps...Jon...educate me...why was oil canning intended on old style oil cans?  I am old enough to remember the refillable oil bottles...

Edited by Wallowa, 09 June 2023 - 03:30 PM.

[ckent323]

Jon,

 

Damping vs dampening. Oil canning vs Tin canning.

You must be a fellow engineer.  Your lexicon gives you away.      




Wallowa, et. al,

Oil Canning Etymology: In reference to the technique used to operate an oil can, holding it between the index and middle fingers while applying pressure to the semi-flexible bottom of the can to pump out oil.

It makes a characteristic sound. 

Generically it got applied to the sound of flexing sheet metal on a variety of assemblies and containers.



Craig

Edited by ckent323, 10 June 2023 - 07:55 PM.

[Wallowa]

Jon,

 

Damping vs dampening. Oil canning vs Tin canning.

You must be a fellow engineer.  Your lexicon gives you away.      




Wallowa, et. al,

Oil Canning Etymology: In reference to the technique used to operate an oil can, holding it between the index and middle fingers while applying pressure to the semi-flexible bottom of the can to pump out oil.

It makes a characteristic sound. 

Generically it got applied to the sound of flexing sheet metal on a variety of assemblies and containers.



Craig

 

 

Craig,

 

I course!  I forgot about the oiling cans with the long narrow spout...I was imaging the oil cans used for vehicle motor oil....the abrupt sound those little cans made is what the top sheet produces but 1K time louder...

 

Thanks..Phil

Edited by Wallowa, 10 June 2023 - 08:10 PM.