Hi Back when these pieces of gear were being made “new”, HP Spokane had a “fan silencer machine”. They used a strobe and a microphone to identify imbalanced blades and then took chunks out of them. They *claimed* it made the fans significantly less noisy….Watching it in action on a noisy factory floor … not so clear.
Bob > On Jul 15, 2016, at 4:25 PM, Tommy Phone <thol...@woh.rr.com> wrote: > > Some thirty years ago fans for automotive radiator cooling were designed with > 7 unevenly spaced blades to reduce the siren effect yet yield comparable air > flow. Careful layout and blade sweep back along with an annular ring made it > entirely feasible to have a statically and dynamically balanced fan as it > came out of the mold. I always wondered why the folks who make these little > fans can't figure out how to do that. Maybe getting comparable CFM from a > much smaller fan violates some Reynolds number requirement for turbulence > control. > > From Tom Holmes, N8ZM > >> On Jul 15, 2016, at 3:52 PM, William H. Fite <omni...@gmail.com> wrote: >> >> That is, in fact, precisely how you do it. >> >> >>> On Friday, July 15, 2016, Orin Eman <orin.e...@gmail.com> wrote: >>> >>> On Fri, Jul 15, 2016 at 10:55 AM, Poul-Henning Kamp <p...@phk.freebsd.dk >>> <javascript:;>> >>> wrote: >>> >>>> -------- >>>> In message < >>>> cany2ixq6onvridofgnfkebqjdkntp7t8kue7boupxjwlcux...@mail.gmail.com >>> <javascript:;>> >>>> , "William H. Fite" writes: >>>>> David Kirkby scripsit: >>>>>> >>>>>> I often here of people replacing fans with quiter ones, but I suspect >>>> that >>>>>> all they really do is reduce the airflow. >>>>> >>>>> Not necessarily, Dave. The Austrian company, Noctua, for one, makes >>>>> extremely quiet fans with excellent airflow. >>>> >>>> ... at zero pressure differential, which is easy to do (Think: ceiling >>>> fan). >>>> >>>> >>> >>> Right. >>> >>> You have to look at the curves on the data sheet that shows air flow vs. >>> static pressure (and be careful about the static pressure scale). I found >>> that a 'quiet' fan would often be flowing one tenth as much air as the >>> original fan at the static pressure at which the original fan was rated. >>> >>> In a given instrument, you may get away with the quieter fan, but how would >>> you tell other than putting a thermometer inside and making a before/after >>> comparison? >>> >>> Orin. >>> _______________________________________________ >>> time-nuts mailing list -- time-nuts@febo.com <javascript:;> >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >>> >> >> >> -- >> Yes, Black lives do matter. >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.