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Hey Tom:  The Bernoulli is actually one of my favorites and in fact  
can be incredibly rich:  Try stacking more than one sphere...slowly  
move a short ring down over the sphere.....place your hand near one  
side of the sphere.........tape some short tinsel to several points  
on the ping pong ball.....

That's the wonderful thing about science center exhibits -- at their  
best, they are a library of experiences - you may get excited by one  
thing, I, another.
	


On May 28, 2009, at 10:59 AM, Tom Nielsen wrote:

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> 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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> For information about the Association of Science-Technology Centers  
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