On Mon, 15 Aug 2011 18:47:26 -0700 (PDT), Jerry Avins <jya@ieee.org> wrote:>On Aug 15, 8:04�pm, "steveu" <steveu@n_o_s_p_a_m.coppice.org> wrote: >> >On Aug 15, 11:03=A0am, Jerry Avins <j...@ieee.org> wrote: >> >> A beautiful demo of many oscillators with a common >> >> sub-period:http://tiny= >> >> >url.com/3ee2eya >> >> >> Jerry >> >> -- >> >> Engineering is the art of making what you want from things you can get. >> >> >That's pretty F***in' cool! I wonder how long it took to "tune" it? >> >> I imagine that tuning was unnecessary. Its just a matter of careful >> assembly, to keeps the balls in a nice straight line. I wonder how much >> practice it took to get a clean release of the entire row, though? :-) > >I think the tuning wasn't easy. The period is proportional to the >square root of length, but the effective length is the distance from >the support attachment to the center of percussion, a point somewhat >beyond the center of mass, and closer to it with the longer strings. >It is easy to get close with a little calculation, but that's like >trying to tune a guitar with a tensimeter. > >JerryHi Jer, I agree with you and Clay. I'll bet the 'tuning' took quite a while. [-Rick-]
OT: Spacial aliasing (or so they claim)
Started by ●August 15, 2011
Reply by ●August 19, 20112011-08-19
Reply by ●August 19, 20112011-08-19
Rick Lyons <R.Lyons@_bogus_ieee.org> wrote: (snip on pendulum waves)>>> I imagine that tuning was unnecessary. Its just a matter of careful >>> assembly, to keeps the balls in a nice straight line. I wonder how much >>> practice it took to get a clean release of the entire row, though? :-)The one I saw didn't have all that good a start.>>I think the tuning wasn't easy. The period is proportional to the >>square root of length, but the effective length is the distance from >>the support attachment to the center of percussion, a point somewhat >>beyond the center of mass, and closer to it with the longer strings. >>It is easy to get close with a little calculation, but that's like >>trying to tune a guitar with a tensimeter.> I agree with you and Clay. I'll bet the 'tuning' took quite a while.My thought while watching was to tune each to resonance. That is, excite the system at the desired frequency, and adjust the length until it reaches that frequency. For a period of 1s, and desire to be not too far off after 60s, the periods have to be somewhat better than 1% accurate. Without trying, I don't know how hard that it to do. -- glen
Reply by ●August 20, 20112011-08-20
On Aug 19, 4:02�pm, glen herrmannsfeldt <g...@ugcs.caltech.edu> wrote: ...> My thought while watching was to tune each to resonance. �That is, > excite the system at the desired frequency, and adjust the length > until it reaches that frequency. �For a period of 1s, and desire > to be not too far off after 60s, the periods have to be somewhat > better than 1% accurate. �Without trying, I don't know how > hard that it to do. �Each change of tuning involves retying two knots, keeping the strings nearly equal lengths. I would find it hard. Jerry -- Engineering is the art of making what you want from things you can get.
Reply by ●August 20, 20112011-08-20
>On Aug 19, 4:02=A0pm, glen herrmannsfeldt <g...@ugcs.caltech.edu> wrote: > > ... > >> My thought while watching was to tune each to resonance. =A0That is, >> excite the system at the desired frequency, and adjust the length >> until it reaches that frequency. =A0For a period of 1s, and desire >> to be not too far off after 60s, the periods have to be somewhat >> better than 1% accurate. =A0Without trying, I don't know how >> hard that it to do. =A0 > >Each change of tuning involves retying two knots, keeping the strings >nearly equal lengths. I would find it hard. > >Jerry >-- >Engineering is the art of making what you want from things you can get. >Don't use knots. They make life very hard, as the shape of the know substantially affects tuning. Some form of simple clamp will work out much easier to tune, as long as you can avoid clumsy people tugging the cord out of place. A simple tight slot may be enough. Steve
Reply by ●August 20, 20112011-08-20
On Aug 20, 11:35�am, "steveu" <steveu@n_o_s_p_a_m.coppice.org> wrote:> >On Aug 19, 4:02=A0pm, glen herrmannsfeldt <g...@ugcs.caltech.edu> wrote: > > > �... > > >> My thought while watching was to tune each to resonance. =A0That is, > >> excite the system at the desired frequency, and adjust the length > >> until it reaches that frequency. =A0For a period of 1s, and desire > >> to be not too far off after 60s, the periods have to be somewhat > >> better than 1% accurate. =A0Without trying, I don't know how > >> hard that it to do. =A0 > > >Each change of tuning involves retying two knots, keeping the strings > >nearly equal lengths. I would find it hard. > > >Jerry > >-- > >Engineering is the art of making what you want from things you can get. > > Don't use knots. They make life very hard, as the shape of the know > substantially affects tuning. Some form of simple clamp will work out much > easier to tune, as long as you can avoid clumsy people tugging the cord out > of place. A simple tight slot may be enough.The video shows no evidence of clamps that I can see. Jerry -- Engineering is the art of making what you want from things you can get.
Reply by ●August 21, 20112011-08-21
>On Aug 20, 11:35=A0am, "steveu" <steveu@n_o_s_p_a_m.coppice.org> wrote: >> >On Aug 19, 4:02=3DA0pm, glen herrmannsfeldt <g...@ugcs.caltech.edu>wrot=>e: >> >> > =A0... >> >> >> My thought while watching was to tune each to resonance. =3DA0Thatis,>> >> excite the system at the desired frequency, and adjust the length >> >> until it reaches that frequency. =3DA0For a period of 1s, and desire >> >> to be not too far off after 60s, the periods have to be somewhat >> >> better than 1% accurate. =3DA0Without trying, I don't know how >> >> hard that it to do. =3DA0 >> >> >Each change of tuning involves retying two knots, keeping the strings >> >nearly equal lengths. I would find it hard. >> >> >Jerry >> >-- >> >Engineering is the art of making what you want from things you canget.>> >> Don't use knots. They make life very hard, as the shape of the know >> substantially affects tuning. Some form of simple clamp will work outmuc=>h >> easier to tune, as long as you can avoid clumsy people tugging the cordo=>ut >> of place. A simple tight slot may be enough. > >The video shows no evidence of clamps that I can see.I can't see any knots, either. The strings seem to got into small holes in a U channel at the top. If I were doing this I'd try small bulldog clips, or maybe even small clothes pegs, in that channel, rather than knots. Steve
Reply by ●August 21, 20112011-08-21
On Aug 21, 1:50�am, "steveu" <steveu@n_o_s_p_a_m.coppice.org> wrote:> >On Aug 20, 11:35=A0am, "steveu" <steveu@n_o_s_p_a_m.coppice.org> wrote: > >> >On Aug 19, 4:02=3DA0pm, glen herrmannsfeldt <g...@ugcs.caltech.edu> > wrot= > >e: > > >> > =A0... > > >> >> My thought while watching was to tune each to resonance. =3DA0That > is, > >> >> excite the system at the desired frequency, and adjust the length > >> >> until it reaches that frequency. =3DA0For a period of 1s, and desire > >> >> to be not too far off after 60s, the periods have to be somewhat > >> >> better than 1% accurate. =3DA0Without trying, I don't know how > >> >> hard that it to do. =3DA0 > > >> >Each change of tuning involves retying two knots, keeping the strings > >> >nearly equal lengths. I would find it hard. > > >> >Jerry > >> >-- > >> >Engineering is the art of making what you want from things you can > get. > > >> Don't use knots. They make life very hard, as the shape of the know > >> substantially affects tuning. Some form of simple clamp will work out > muc= > >h > >> easier to tune, as long as you can avoid clumsy people tugging the cord > o= > >ut > >> of place. A simple tight slot may be enough. > > >The video shows no evidence of clamps that I can see. > > I can't see any knots, either. The strings seem to got into small holes in > a U channel at the top. If I were doing this I'd try small bulldog clips, > or maybe even small clothes pegs, in that channel, rather than knots.That seems good. Jerry -- Engineering is the art of making what you want from things you can get.
