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Re: AH Supply -- Fans, noise, and mounting

"S. Hieber" <shieber at yahoo_com> wrote

> Ivo Busko said:
> < Months ago I bougth from them (AH Supply) a small AC fan (2"
> > diam. 
> > as far as I recall). Complete with fan guard, dust filter and
> > mounting screws,
> > I think I paid around $24 for it. They are not advertised at their
> > web site, 
> > I spoke with Kim directly. The fan turned out to be very good indeed,
> > low 
> > flow rate but *extremely* quiet, which was the feature I was looking
> > for.
> > I don't know it's specs though.
> > 
> > I ended up not using it in my DIY strip light not because of the fan
> > itself, 
> > but because I was unable to mount it on the strip's wood frame in a
> > way that 
> > prevented it to hum annoyingly. The frame, not the fan. I tried
> > everything 
> > I could to mechanically decouple it from the frame with no avail.
> > Well, DIY 
> > has its drawbacks too. 
> [[[[I haven't used the AH Supply fans but the fans I ahve used I have
> mounted directly with stainless steels screws
> (http://www.mcmaster.com/) using rubber grommets between the fan and
> hood or else without the grommets -- sometimes I can get away with this
> - -- sometimes not.   But I assume you tried this and still no luck. 
> What is you hood made of, if you don't mind my asking?]]]]]

Yes, I tried rubber grommets among other things. The hood always hummed.
It could be some sort of acoustic coupling, not a direct mechanical one,
I don't known. The hood is built around a commercial aluminum reflector
designed for "troffer" (sp. ?) recessed fixtures. I built a very light
wooden frame around it mostly to block light that comes out at its ends, 
and to get a rigid fixture. The reflector by itself cannot stand handling
without bending and twisting. Maybe this is why it's so sensitive to
vibration. I also wanted a very low profile. I designed the fixture 
initially to hold just two 55 Watt PCs. In that configuration it would 
rely entirely on radiative and convective cooling The aluminum reflector 
is completely exposed to the ambient air and painted black, it is as 
close to a perfect radiator as I can get. When I added two more PCs I felt 
some sort of assisted cooling was necessary. I plan to revisit this problem 
in the future. It turns out that the fixture does not have to be so low in 
profile anyway, I have about 1" - 1.5" to spare in height before it gets 
visible behind the front light strip (a converted AGA dual fluoro strip
added later to the project). By raising the fixture and providing some air 
passages I may be able to get back into passive (and silent !) cooling.

- Ivo Busko
  Baltimore, MD

  "Buy a fish, Save a tree !"
  Project Piaba: http://www.angelfire.com/pq/piaba/