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I'm not sure how well they'd work, but Panasonic makes some pretty quiet fans that put out around 80cfm or more through a 4" pipe.

 - Len



>>> On 5/28/2009 at  8:59 AM, in message
<[log in to unmask]>, Tom Nielsen <[log in to unmask]>
wrote:
> ISEN-ASTC-L is a service of the Association of Science-Technology Centers
> Incorporated, a worldwide network of science museums and related 
> institutions.
> ****************************************************************************
> *
> 
> Erich,
> 
> I have found most versions of "Bernoulli Blower"  -- even the  
> Exploratorium's, when it's placed in a smaller space -- to be too loud  
> for my taste.  ( I suppose in truth the "modern world" is too loud for  
> my taste, but what's to be done?)  There is a direct tradeoff between  
> the CPM and the noise, but other factors are important too.  The path  
> the air takes as it leaves the blower, and the aperture where it exits  
> create resonances that shape the character of the sound.  We had a  
> quite powerful squirrel cage blower in San Jose, driven by a 230 volt   
> 3 phase induction motor.  Someone discovered (or was brilliant enough  
> to know) that placing a tennis ball at the aperture magically lowered  
> the noise while only slightly reducing the height at which the ball  
> flies.  The blower was also housed in a box lined with acoustic foam,  
> fitted with air filters  on the intake to avoid sucking in strings and  
> such and a grill on the outlet to keep coins etc from being dropped in.
> 
> My preference, to avoid all that bother,  is to forgo the heavier  
> balls usually used, and go with balloons and a small quiet ventilating  
> fan.   Yes, you will need to replace the balloons constantly, but  
> then, beach balls don't last very long either -- and anything more  
> durable takes considerably more air to lift.
> 
> Lastly, for all that it has been replicated over the years, I don't  
> think the "Bernoulli Blowers" is a particularly rich exhibit, compared  
> to the "air play table" you also mention.  The latter doesn't really  
> need much air to be effective.  Here, for example, is a wonderful  
> alternative, also from the Exploratorium, that uses just a window fan:
> 
> http://www.exploratorium.edu/pie/library/windtubes/index.html 
> 
> quietly,
> 
> Tom Nielsen
> www.TheExhibitGuys.com 
> 
> On May 28, 2009, at 7:17 AM, Erich Rose wrote:
> 
>> ISEN-ASTC-L is a service of the Association of Science-Technology  
>> Centers
>> Incorporated, a worldwide network of science museums and related  
>> institutions.
>> 
> *****************************************************************************
>>
>> For an "air play table" or a Bernoulli blower what would you suggest  
>> as a minimum air flow? CFM? I have used different fans in the past  
>> with different results. More often than not they were used squirrel  
>> cage fans that we had laying around and had a wide variety of  
>> outputs.  What I am looking for is some feedback from others about  
>> what they found worked best.
>>
>> --
>> Erich Rose
>> Exhibit, Environmental and Industrial Design
>> 807 The Living End
>> Austin, TX 78746
>> 512-626-9930; [log in to unmask] 
>>
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