[CAUT] More on Single String Beats

[RicB]

Hi Fred

I agree with very much of what you say below. Especially the point you 
make about the practical usefulness of using CA or Epoxy in bridge pin 
holes relative to helping reduce the occurrence and severity of single 
string beats.  I remain unconvinced however that it has so directly very 
much to do with the pin being firmly rooted in the hole... if for no 
other reason then because I find so many many instances where a pin is 
very loose and there is no beat... and instances where a pin is tight as 
a whistle in a keyhole where there are beats.

I agree also 500 % that crisp and precise terminations definitely are 
desirables relating to clean sound... tho to what degree these relate to 
the single string beat phenomenon is another question.

Good point on the experiment I suggest. And I agree that increased side 
pressure would tend to counter any increase in flagpoling. That said, 
one of the main arguments for flagpoling as a source of single string 
beats is that the surface area of the bridge face (to about 1-0.5 mm 
deep) is not able to hold the pin tightly in the first place.  There is 
already quite considerable side bearing pressure on the pin to hold the 
pin firmly pushed to the far side of the hole already as it were. I 
admit I havent any mechanics numbers on hand to back up the postulate... 
but I think holding the pin so loosely and so far up in the <<air>> as 
it were would indeed result in a net lessening in its ability to stay 
stiff in the face of string vibrations.  In anycase, you can do the same 
experiment with vertical pins and find what amount to the same results. 
I did quite a bit of work with a vertical notched bridge pin solution a 
while back in developing an alternative to present day bridge agraffes 
and bridge / bridge pin terminations a while back. That actually that 
was one of the things that got me started off on all this single string 
beating thing.

Cheers, and mucho appreciatos for the dialog so far to one and all.

RicB


        On Apr 16, 2007, at 5:29 AM, RicB wrote:

         > There is so much micro movement going on between the bridge / 
         > bridge pins / bridge interface with the soundboard that is on a 
         > scale large enough to contribute directly to a single string
        beat 
         > condition that it is actually quite surprising the loose pin 
         > explanation got started in the first place... let alone
        gained so 
         > much steam.


    Hi Ric,
        Interesting thoughts on the "false beat" phenomenon. As to why the 
    loose pin explanation got started: when it is possible in many, many 
    cases to clear up false beats by adding a "filler" material next to 
    the pin, one begins to make assumptions <g>. I guess your contention 
    is that in applying those materials (CA, epoxy) you are doing more to 
    stiffen the termination area than to fill the gap. Could be. One way 
    or another, it has a lot to do with the pin being firmly (relatively 
    speaking) rooted.
        I think some high speed videography might yield real information
    on 
    this issue, as opposed to the conjectures we mostly deal with. Taking 
    a string that is producing a noticeable false beat, focusing close up 
    on the bridge pin, seeing whether the pin itself moves, and whether 
    there is a regular frequency that can be associated with the 
    frequency of the false beat.
        In any event, from a practical standpoint CA and epoxy are good 
    cures for much falseness. Crisp terminations (well shaped capo or 
    machined/polished agraffes, new bridge pins without nicks and 
    grooves, pins firmly held by the bridge, good notching) yield clean 
    sound, in my experience.
        As to your experiment of placing a centerpin between string and 
    bridge cap, I'm not sure it proves anything about loose bridge pins 
    (maybe it says something about notching). By raising the string up 
    the angled pin, you are greatly increasing the side pressure on that 
    pin, hence "stiffening it against the side of its hole." You are also 
    somewhat increasing the lever advantage of the string versus the pin, 
    increasing that effect (of pushing it firmly against the far side of 
    the hole). So I think, contrary to your reasoning, that you are 
    reducing the likelihood of flagpoling.
    Regards,
    Fred Sturm
    University of New Mexico
    fssturm at unm.edu
    --