The "Jolly Loop" (Modified by Kent Swafford)

[Delwin D Fandrich]

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From: pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org] On Behalf Of
Roger Jolly
Sent: April 15, 2005 11:34 PM
To: Pianotech
Subject: RE: The "Jolly Loop" (Modified by Kent Swafford)


At 11:34 PM 4/8/2005, you wrote:






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    I have too much evidence to the contrary.  The end of the knot becomes a
theoretical termination point, and the helix is almost incapable of flexing. 



I'd sure like to see it. With vertical hitches the string doesn't have to flex,
it pivots at the hitchpin itself. The twist is of no consequence.


A very interesting hypothesis.  We may as well stop calculating inharmonicity,
on the bare section of core wire, in the speaking length.  Or is that also of no
consequence?  Is the stiffness of the swage also of no consequence? 
The hitch termination has an effect on the control of bearing and is indeed a
great asset in design.  However when you double the thickness of the wire over
about 50% of the back scale length and mass load it with 3-4 complete turns at
the end of the knot. It sure as heck as an effect on the flexibility of the back
scale. 

Now, let's not take what I said out of context. This issue has nothing to do
with inharmonicity. It has to do with whether or not the string is bending
anywhere close to the hitch pin when a vertical hitch pin is used. With the
vertical hitch pin arrangement the backscale essentially pivots at the hitchpin.
The string is not required to bend up in the twisted portion of the backscale.
 
 

So many pianos have about a 55mm knot at A0,  and only about 7-10mm of flexible
string.  James had a clear demonstration model at the Cal state convention.  The
reaction of all that saw it was wow! The vibration time of the new knot vs an
English loop is about 3 times greater.



I can see this if it is compared to a conventional hitchpin system. But not if
it is compared to a vertical hitchpin system.


It is the bridge that sets the back scale in motion.  Bearing and back scale
flexibility interact, and has a profound effect on how the bridge is going to
react..   You are trying to say that the stiffness of the helix and mass loading
of the knot has no effect on flexibility?    Plucking the back scale of the
small Walter's grand still sounds fairly dead to me.  And that is a fair clue to
a stiff back scale. 

I'm aware of this, Roger. I'm the one who has been teaching classes on the curse
of the short backscale and the stiffness of the twisted portion of the
conventional bass string for the past 25 years, remember? So, no, of course I'm
not saying the stiffness of the helix has no effect on the flexibility of the
wire. But I am saying that it doesn't matter to the mobility of the bridge
whether or not there is much of any flexibility in the backscale when vertical
hitches are used. This is the whole point of the vertical hitchpin.
 
You points are well taken when you are comparing the English loop (or the German
loop -- take your pick) with the standard, or conventional, hitchpin
arrangement. But not when they are compared to the vertical hitchpin. With the
vertical hitchpin termination something less than the back half of the loop is
the only contact point between the string and the back termination pin. The
backscale length is not effectively clamped down as it is with the conventional
hitchpin arrangement. Try it for yourself -- take a vertical hitchpin, clamp it
in a vice and loop a conventional bass string over it. Move the string up and
down and see if the thing has to bend anywhere in the twisted portion of the
string.
 
I'm not trying to diminish the effectiveness of the English loop in any way. I'm
just trying to correct what I see as a mistaken perception of how the vertical
hitchpin system functions. I still see it as the preferable of the three
different systems.

 

To the previous writer, it is not Del's hitch pins.  But was developed and
patented by Harold Conklin of the Baldwin piano company. 



The vertical hitch pin that I most often use is some different than that used by
Baldwin. It is this difference the writer was referring to not the invention of
the system.
 
And, for what it's worth (and with respect to Mr Conklin's many other
achievements), when I was at Baldwin I was told by both Bob Cutshall (then head
of engineering) and Bob Farris (then chief piano engineer) that the actual
inventor of the vertical hitch and the floating plate mounting system was a
piano technician/rebuilder who worked in the R&D shop.


I was lead to believe the patent reads H. Conklin and the Baldwin Piano Company.
I guess I am corrected? 

Baldwin's name is there as the patent owner by virtue of assignment. As I recall
there are other names on the patent as well. I'd have to do a search for the
number and look it up (it's a pre-1976 patent). As may be, I'm just passing on
what I was told by folks who were there at the time.
 
Del

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