ISEN-ASTC-L is a service of the Association of Science-Technology Centers
Incorporated, a worldwide network of science museums and related institutions.
*****************************************************************************

Still waiting for those formulas?

I've designed and built TOO many of these now.  Each one ends up behaving differently for different reasons. Along with the size of the ball and the power of the blower/fan, there will be issues with outlet path and size.  One bend in the path or a path that is not smooth can drastically change the way it behaves. Many blower fans have ratings at  different static pressures.  I believe that has a great dal to do with the path the air moves through (as in more or less bends).

If you build one like the classic Exploratorium unit with a large fan, traffic cone and wire mesh screen you quickly learn that the wire mesh they suggest doesn't keep everything out.  And a fine mesh screen can impede the flow substantially.  I had one occasion where someone managed to get a small golf pencil down thru the 1/4" mesh and then the blower fan proceeded to spit splinters at the visitors!  It had been built (not by me) so that it was impossible to get at the fan without major disassembly.  We (several staff) had to pick the entire cabinet up, turn it upside down, and shake all the pencil fragments out of it.  I have designed all since with a compartment to catch stuff before it gets to the fan.  But that means bigger fans because the compartments create turbulence.

Bottom line is you have a great many more factors than just fan and ball size.

Erich Rose

Erich Rose Design
807 The Living End
Austin, TX 78746
512-626-9930; [log in to unmask]

> 
> Jeff Courtman <[log in to unmask]> wrote:
> 
>> I'm sure there are folks out there that have already taken a stab at this,
>> but didn't find anything in the archives:
>> 
> 
> 
>> For instance, if I know the weight of the ball and the diameter, is there
>> an easy (reasonably) way to get in the ballpark with regard to air delivery,
>> size of the air column, amount of lift, etc......?  Or am I just walking
>> down a primrose path?


***********************************************************************
For information about the Association of Science-Technology Centers and the Informal Science Education Network please visit www.astc.org.

Check out the latest case studies and reviews on ExhibitFiles at www.exhibitfiles.org.

The ISEN-ASTC-L email list is powered by LISTSERVR software from L-Soft. To learn more, visit
http://www.lsoft.com/LISTSERV-powered.html.

To remove your e-mail address from the ISEN-ASTC-L list, send the
message  SIGNOFF ISEN-ASTC-L in the BODY of a message to
[log in to unmask]