>Michael
>Were the old swan necks repaired or left in their >deformed
>state, assuming it is possible to tell this from looking at >it?
Marion,
I personally drew up some plans of the Yale Jauch, and noticed the
extension was in absolute perfect playable condition. There were other
problems with it but the neck was fine. Also Hoppy Smith made a recording
using the 1755 Widhalm with a swan neck, as well as the swan neck Hoffman,
and the Martin Brunner.
The only problems I've heard associated with swan necks were made by
contemparie makers, who used the wrong kind of woods, and didn't copy the
design properly, and this only in the early days. Now everyone has it down.
I used the word explode, but you seem to give the impression that the
swan neck will self destruct, which obviously isn't true. BTW are you a
lute maker as well?best,
All the
Michael Thames
www.ThamesClassicalGuitars.com
----- Original Message -----
From: "Dr. Marion Ceruti" <[EMAIL PROTECTED]>
To: "Michael Thames" <[EMAIL PROTECTED]>
Cc: "Lute List" <lute@cs.dartmouth.edu>
Sent: Tuesday, March 15, 2005 12:28 AM
Subject: Re: Bent peg box
> Dear Michael,
>
> Whereas some people think it's a problem, others see it as
> an advantage. Like so many things, there are advantages
> and disadvantages. How does a luthier compensate?
> Assuming you did not like this effect, what kind of a repair
> would the luthier do to fix it? Have you had this done and
> is it expensive? (So far, I like mine the way it is, unless
> someone can convince me that it is really a bad thing.)
>
> I hope it lasts longer than I will. If it falls apart that fast
> I've got problems. :)
>
> It is not clear how my explanation sounds like the lute will
> explode. This is a very gradual effect.
>
> Were the old swan necks repaired or left in their deformed
> state, assuming it is possible to tell this from looking at it?
>
> Best Regards,
> Marion
>
> -----Original Message-----
> From: Michael Thames <[EMAIL PROTECTED]>
> Sent: Mar 14, 2005 8:39 PM
> To: "Dr. Marion Ceruti" <[EMAIL PROTECTED]>,
> Richard Corran <[EMAIL PROTECTED]>,
> Lute List <lute@cs.dartmouth.edu>
> Subject: Re: Bent peg box
>
> ++In reference to the deformation that occurs in swan-neck
> lutes, we have a slightly non-equilibrium situation. The forces
> are not exactly balanced and over a period of time the string
> tension overcomes the rigidity of the neck. It will overpower the
> neck in the place of least resistance, namely in the swan part of
> the neck
>
> Marion,
> This isn't a problem. Of course the swan neck pegbox will bend
> forward under initial tension. A lute maker will compensate for this, once
> everything is adjusted it will last longer than you. You make it sound
like
> the whole thing will explode. Of course, Everything's impermanent, at
some
> point, but so far the swan neck lutes I've seen built 250 years ago are
> fine.
> Michael Thames
> www.ThamesClassicalGuitars.com
> ----- Original Message -----
> From: "Dr. Marion Ceruti" <[EMAIL PROTECTED]>
> To: "Richard Corran" <[EMAIL PROTECTED]>; "Lute List"
> <lute@cs.dartmouth.edu>
> Sent: Monday, March 14, 2005 3:16 PM
> Subject: Re: Bent peg box
>
>
> > Dear Richard,
> >
> > Please see my comments below ++.
> > _______________________
> > There are a number of misunderstandings about the forces on a peg box.
> >
> > First of all the only force transmitted to the peg box comes from the
> > strings.
> >
> > ++The other forces besides the transmited force are friction and the
> > electrostatic forces inside the molecules that maintain rigidity in
> > the neck, pegs, etc. without which the neck would collapse when the
> > tension was applied. These forces are equal and opposite to the applied
> > force, resulting in an equilibrium situation in which there is no
> > apparent change.
> >
> > Bending them around a corner doesn't make much difference to
> > the force in magnitude (it decreases a little due to friction although
> > depending on whether the tuned note is approached from above or below
> > in pitch, it can actually be higher than the tension in the sounding
> > part of the string.) So peg boxes are not bent back to reduce the
> > force.
> >
> > ++Actually, bending a line, cord, rope, or string around corners
> > produces a great deal of force in the form of friction, which always
> > opposes motion. It is friction that keeps our pegs from rotating
> > when set in a certain position (in theory). This is why we have
> > capstans on boats. The more turns around the capstan, the
> > greater the friction and the better the advantage. Friction originates
> > from the forces already resident in the material (which are balanced
> > in the absence of a perturbation.)
> >
> > It does, of course, change the direction but so what?
> >
> > ++It redistributes the force. This change consititues the perturbation
> > necessary to produce friction.
> >
> > Secondly the force on an individual peg is also practically identical
> > whatever the angle of the peg box.
> >
> > ++The difference is the force distribution. The interesting part
> > happens at the nut, not so much at the pegs, however much
> > they may deform also over time.
> >
> > Again the peg will deform the same amount whether the peg box
> > is bent back or not and this goes for immediate response of creep
> > over a longer period of time.
> >
> > ++In reference to the deformation that occurs in swan-neck
> > lutes, we have a slightly non-equilibrium situation. The forces
> > are not exactly balanced and over a period of time the string
> > tension overcomes the rigidity of the neck. It will overpower the
> > neck in the place of least resistance, namely in the swan part of
> > the neck. The longer the neck, the more pronounced the
> > effect for the same initial tension. This is why it is easier to
> > bend a 30-meter metal rod than it is to bend the a rod of the
> > same material and diameter if it were 5 cm.
> >
> > The nature of tuned instruments is to keep the tension constant
> > so the pitch is maintained.
> >
> > ++At equilibrium when forces are balanced.
> >
> > Thirdly there is no mechanical advantage in a system with only one
> > "pulley" as the nut is supposed to be. If you hang a single pulley
> > from the ceiling, put in a rope and attach a weight, you have to pull
> > with a force equal to the weight (plus a little for friction perhaps)
> > in order to lift the weight. To get a mechanical advantage you must
> > increase the number of pulleys. This clearly doesn't happen on lutes.
> >
> > ++Maybe a pulley is not the best analogy because in a pulley, you
> > have a rotating part that is designed to reduce friction, and friction
> > is important to the function of lutes.
> > (If one pulley alone produces 0 mechanical advantage and another
> > pulley alone also produces 0, how do you add or multiply them to get a
> > non-zero number? When I get the chance I will find the formula that
> > relates the number of pulleys to the force reduction, but this is not
> > related to lutes.)
> >
> > Fourthly since the forces arise from the strings on both the bridge and
> > nut, whether the peg box is bent back or not has no effect on how the
> > action changes over time unless the strings simply don't touch the nut.
> >
> > ++The action increases when the weakest part of the swan neck
> > deforms in the direction to decrease the tension. The neck is not
> > at equilibrium or nothing would ever move.
> >
> > This in unlikely. The change in action over time is associated with
> > the set up of the lute, the choice of materials, and the pitch to which
> > it's tuned together with the strings. Getting a combination of these
> > less than optimum is likely to lead to problems.
> >
> > ++The set up or geometry of the lute is important. The bend in the
> > pegbox keeps all strings at the same height at the nut, even if the
> > pegbox bends from, say 90 degrees to 60 degrees. However, a 30-
> > degree bend in a swan neck would produce a major change in action.
> > The choice of materials relates to the composition of the parts,
> > again originating in the differences between molecules. Different
> > molecules have different intermolecular forces, which give rise to
> > different tensile strengths and differernt frictional characteristics.
> >
> > I conclude that the angled peg box has two advantages: firstly it helps
> > to keep the centre of mass of the lute nearer the rose thus making the
> > lute easier to hold and secondly it looks more balanced. Of course
> > the latter is in the eye of the beholder.
> >
> > ++The pegbox redistributes the forces to transmit tensile force from
> > the string to produce friction on the nut. At an angle of 0 degrees,
> > (straight line) the strings produce near zero force on the nut. (No lute
> > I have seen has a zero angle. The angle is always at least a small
> > non-zero value.) If you increase the angle on the pegbox from zero
> > to 90, which is the maximum, you will increase the friction on the nut
> > according to the sine of the angle. This is why you will not see a
> > pegbox set at an angle greater than 90 degrees. The function may
> > be more complicated than a simple sine function, but this is the main
> > effect. (To get more specific, I would have to think about what else
> > could contribute to changes in the friction, such as temperature and
> > string composition, string-surface fine structure.)
> >
> > Sorry to sound so pompous. Put it down to my being a mechanical
> > engineer.
> >
> > Richard Corran
> >
> > ++No offense taken. Thank you for continuing this discussion on an
> > objective, scientific, and logical level that is free from hatred, snide
> > remarks and personal insults.
> >
> > Best regards,
> > Marion Ceruti, Ph.D. in physical chemistry
> > Senior Member, IEEE
> >
> >
> > To get on or off this list see list information at
> > http://www.cs.dartmouth.edu/~wbc/lute-admin/index.html
> >
> >
> >
>
>
>
