Bridge Seating

[Ric Brekne]

Alan Forsyth writes:

    I have this piano where every single string is false. I know it is
    not the bridge pins because there are no bridge pins. Another form
    of clamping the strings to the bridge is being used. ( I'll leave
    you to imagine what that might be).

Curious, I wonder if the false beating would respond to anything like 
the screwdriver trick.


    Now, as for the cause, we have to start from the very beginning. A
    false beat is two different frequencies produced by the same string.
    To have two frequencies produced can only be caused by changes in
    either the speaking length or a change in the tension of the string.
    What is the actual mechanical link between a loose bridge pin and
    either of the above causes? Does a loose bridge pin create changes
    in tension or changes in the speaking length of the string?

    AF

The thing is, nobody really knows what that mechanical link is (or if it 
really is for that matter), tho some will no doubt claim they do. Yet 
the only explanation I've heard so far is easily disproved in a few 
minutes by artificially creating those exact conditions in a small 
selection of treble strings.  Take your next nasty false beat string 
along with another clean string.  Change pins and see what happens,  
Then try putting in an overly loose pin and see what happens. If you do 
this enough you will find the degree of randomness is to significant to 
be ignored.

Why exactly CA helps sometimes and not others remains IMHO unsolved.  
And it wont ever get solved as long as we simply accept the latest 
answer in fashion. Thats what irks me about this whole discussion.  We 
have a situation in which a stated theory has clearly far to many 
exceptions to be valid. Yet in the name of the  <<pursuit of truth>>  
this fact is simply dismissed without further thought.

Strictly speaking... we dont really need an answer to why CA or epoxy 
often helps.  But on the other hand who knows what benifits an answer 
might provide. I think that we need to put the numbers and physics, such 
as they are, on the back burner and do some hardcore practical process 
of elimination testing.  Nothing like real life observation of as many 
conditions as we can think of to help shed light on a subject.  Here are 
a few things I've tried: 

-- inserting an overly loose pin in a bridge pin hole for both a known 
false beat offender and a clean string.
-- inserting various devices (center pins, thin brass plates, etc behind 
the pin(s) to raise the string about 0.5 mm off the bridge pin. Again 
both for known false beat and clean strings.  Actually this seems to 
clean up pretty well as much false beating as  CA'ing the pins does.
-- checking how many false beating strings actually have loose pins and 
how many have very tight strings.
-- keeping track of the condition of these same over time. 
-- checking to see whether or not an offending string has the infamous 
crushed notch edge.
-- applying other substances to see long and shorterm affects.  Try a 
drop or two of water (use on a beater only please) for example.  Pins 
get tight as all get out for a short time... but again the results are 
random.
-- change strings... and oldy but goody.  Why on earth would this work 
even once if the cause was something completely independent of the 
string itself eh ?

All I find so far is that the things I have tested for yeild random 
results from a strictly statistical point of view.

I'd love to hear other ideas as for things to look closer at. 

Cheers
RicB