The consideration in trying to reduce the weight of the needle holder in
acoustic soundboxes is not the weight of the needle holder compare with the
total weight of the soundbox but as its weight increases the weight and
mass of the vibratory train whose of which
total mass it can be a significant fraction. The more mass in the
vibratory train, the more inertia that limits high frequency response.
Also the position of the mass is important, the closer to the pivot the
less detriment.
Jim
Cartwright
Immortal
Performances
[email protected]
EarthLink Revolves Around You.
> [Original Message]
> From: Bob <[email protected]>
> To: Antique Phonograph List <[email protected]>
> Date: 2/14/2008 7:49:23 AM
> Subject: Re: [Phono-L] threaded needles
>
> Hi Greg,
> I've read this whole discussion with interest. As I understand it
the
> goal of this exercise in "mental masturbation" is to reduce the mass of
the
> reproducer by the weight of the thumb screw. I do not have accurate
> measuring tools to weigh a standard thumb screw and don't remember the
> weight of your custom aluminum reproducer but emphericly I don't think
the
> thumbscrew makes up a significant proportion of the total mass which is
why
> I made the comment about mental masturbation. That being said, I do have
a
> practical solution to eliminate most of the mass of the thumbscrew. I
would
> think the majority of the mass of the thumbscrew is in the knurled disk
at
> the end used for tightening it against the needle. This section and a
good
> portion of the threaded shaft could be eliminated if you machined a hex
or a
> flat on the end that is left sticking out of the needle bar after the
needle
> is inserted and tightened. You would use either a small pair of pliers
or a
> custom hex wrench to tighten the threaded piece.
> RMV
> ----- Original Message -----
> From: "Greg Bogantz" <[email protected]>
> To: "Antique Phonograph List" <[email protected]>
> Sent: Wednesday, February 13, 2008 4:33 PM
> Subject: Re: [Phono-L] threaded needles
>
>
> > Thatcher,
> >
> > That's essentially what I am now doing. The present design is a
press
> > fit of the needle shank into the hole (deep well, actually) in the
needle
> > bar. But the fit must be tight to prevent rattling. This makes the
> > machining difficult, but more significantly, it makes the needle
exchange
> > difficult because you must use pliers, tweezers, or some similar tool
to
> > hold both the needle bar and the needle shank for both insertion and
> > removal. Not user-friendly. Specialized tools and/or jigs could be
> > furnished to make the job easier, but it's still a tedious task. A
friend
> > of mine has experimented with a similar design. His solution is to
glue
> > the needle shank into the needle bar. That works, but getting the worn
> > needle out of the needle bar is a b*tch. He gets around this by using
the
> > "semi-permanant" osmium Pfanstiehl needles that were popular in the
1940s
> > and can last for several playings. I don't agree with this because
these
> > needles are too hard, as I've commented before, and must be worn in
over
> > several playings on junk records to form their flats. He removes the
> > needle by heating the glue with a soldering iron to cause it to flow.
> > Still, very tedious.
> >
> > Greg Bogantz
> >
> >
> >
> > ----- Original Message -----
> > From: "Thatcher Graham" <[email protected]>
> > To: "Antique Phonograph List" <[email protected]>
> > Sent: Wednesday, February 13, 2008 3:16 PM
> > Subject: Re: [Phono-L] threaded needles
> >
> >
> >>
> >> As an engineer I could not help but to fixate on this "threaded needle
> >> idea". I agree that threading needles solves the mass issue hence the
> >> instinctive appeal, but the difficult manufacture is equally
> >> discouraging. As an alternative, have you considered a sabot?
> >>
> >> -Thatcher
> >>
> >>
> >>
> >> Jon Noring wrote:
> >>> Greg wrote:
> >>>
> >>>
> >>>> Threading the needle shank and having it screw into the needle
bar
> >>>> is an
> >>>> option. I hadn't considered that before, but it would pretty well
> >>>> solve the
> >>>> extra mass problem. But it would make the needles pretty involved
to
> >>>> manufacture. I'll keep it in mind.
> >>>>
> >>>
> >>> Yes, it would be involved if all the needles are threaded by hand or
> >>> in small numbers, especially at the diameter being considered.
> >>>
> >>> It is intriguing to consider using a very fine threaded rod, if even
> >>> manufactured in the desired material(s). One would have to grind and
> >>> polish to create the tip geometry.
> >>>
> >>> Which brings up the idea that if a needle is to be especially
> >>> manufactured, one could consider tipping it with a different material
> >>> that can be specially shaped (such as spherical or elliptical with
> >>> no sharp edges at all. It is my understanding that most damage to
> >>> grooves is due to a tip which is no longer smooth. Maybe the tip could
> >>> be made from a material of the same hardness as the "grit" used in
> >>> shellac discs (is it corundum?) to wear down the needle.
> >>>
> >>> Just thinking outside the box...
> >>>
> >>> Jon
> >>>
> >>> _______________________________________________
> >>> Phono-L mailing list
> >>> http://phono-l.oldcrank.org
> >>>
> >>
> >>
> >>
> >> _______________________________________________
> >> Phono-L mailing list
> >> http://phono-l.oldcrank.org
> >
> > _______________________________________________
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>
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