<VV> Fans/.my take

[ScottyGrover at aol.com]

In a message dated 8/29/2007 11:17:47 A.M. Pacific Daylight Time,  
chsadek at comcast.net writes:

Scotty,

You are doing well, making progress and getting ideas  from folks.  You might 
talk to those custom fan guys who have the  backwards blades-I think for 
material handling more than for air, but? Get  to a tech guy and he might 
really be able to help.  Separate the iris  problem from the control... Look 
for the iris that is movable or  adjustable. First versions can be fixed and 
pretty simple. Later we can  come up with a neat one.

The control can be a separate  search/discussion by folks. Home dryers use a 
vacuum switch that is  adjustable. Allows a current to flow when pressure is 
exceeded or beneath  a pressure. This is what we use on the race cars to 
detect loss of fan.  Turns on a large light on the dash.

Chuck  S




Part of the trouble is that iris dampers are hard to find; most of the  posts 
on the 'Net are from England.  When I last was reading plans (in  2005), they 
weren't being specified. The old customers that I still keep in  touch with 
haven't heard of them.  
As for control, some makes have a sliding lever rotating in a slot in the  
fan housing; I suppose a pivoting motor with a screw-threaded shaft running in a 
 nut on the sliding lever might do the job, but that, or alternative controls 
 require some more thought.  
I've been looking at magnetic couplings for fan drive, thinking that  
something that could slip when the fan was overloaded so as not to run the fan  at 
RPM's that drag down the engine would be acceptable; I've not found anything  
that isn't g**-awfully complicated (eddy-current clutch or just magnetic  
coupling.)
I suppose I could design something  in the KISS line, but I can't be  sure of 
the reliability of the thing.
 
Scotty from Hollyweird



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