PABST KG in the Black Forest (Germany) made very quite high efficient fans, HP used to use these fans for awhile, but the company was sold and the quite fans disappeared, the new fans from the new owner http://www.ebmpapst.us/en/ are cheaper but not so good 73 KJ6UHN Alex On 7/15/2016 1:25 PM, Tommy Phone 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 <omniryx@gmail.com> wrote: >> >> That is, in fact, precisely how you do it. >> >> >>> On Friday, July 15, 2016, Orin Eman <orin.eman@gmail.com> wrote: >>> >>> On Fri, Jul 15, 2016 at 10:55 AM, Poul-Henning Kamp <phk@phk.freebsd.dk >>> <javascript:;>> >>> wrote: >>> >>>> -------- >>>> In message < >>>> CANy2iXq6ONvriDoFgNFkEBQjDKntP7t8KuE7BOUpxJWLCuxLsw@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. > > > ----- > No virus found in this message. > Checked by AVG - www.avg.com > Version: 2016.0.7688 / Virus Database: 4627/12619 - Release Date: 07/15/16

PABST KG in the Black Forest (Germany) made very quite high efficient fans, HP used to use these fans for awhile, but the company was sold and the quite fans disappeared, the new fans from the new owner http://www.ebmpapst.us/en/ are cheaper but not so quite 73 KJ6UHN Alex On 7/15/2016 1:25 PM, Tommy Phone 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 <omniryx@gmail.com> wrote: >> >> That is, in fact, precisely how you do it. >> >> >>> On Friday, July 15, 2016, Orin Eman <orin.eman@gmail.com> wrote: >>> >>> On Fri, Jul 15, 2016 at 10:55 AM, Poul-Henning Kamp <phk@phk.freebsd.dk >>> <javascript:;>> >>> wrote: >>> >>>> -------- >>>> In message < >>>> CANy2iXq6ONvriDoFgNFkEBQjDKntP7t8KuE7BOUpxJWLCuxLsw@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. > > > ----- > No virus found in this message. > Checked by AVG - www.avg.com > Version: 2016.0.7688 / Virus Database: 4627/12619 - Release Date: 07/15/16

Every box I own has AT LEAST one temp sensor in it... I often add 10 or more when redesigning the thermal control for a piece of equipment.... ______________________ Clay Autery, KY5G MONTAC Enterprises (318) 518-1389 On 7/15/2016 1:40 PM, Orin Eman wrote: > > 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.