string seating -- Vladan

[Ric Brekne]

Hi Vladan.

I look forward to seeing this someday.

I think the main point here is that its no good trying to look at just 
one aspect of this subject, throw a few of numbers together to form half 
baked models that dont take into consideration more then a small part of 
the total picture, and try and declare one <<knows>> whats is or what is 
not going on. I must again say I appreciate Phils cautious approach in 
this regard.    Alan Bernard had it dead right the other day.  No one 
really knows why strings can find themselves slightly away from the 
bridge.  One can clearly identify some contributing factors but thats a 
long shot from declaring a full and final answer. 

To declare that string seating does no good at all is of course just 
plain wrong. To further declare that it is never more then a very 
temporary solution is also wrong, and given the argumentation used to 
justify that claim it is also a self contradiction.   On the one hand it 
is stated that the clamp  the bridge pins constitute is too strong to 
allow the string to migrate up the pins in any fashion and indeed the 
dynamics of the system in motion  contribute to a re-enforcment of this 
clamping, whilst they on the other hand are not strong enough to ensure 
contact in the case of even very slight negative bearing  at the front 
edge of the bridge.  Then too.. the pins are able to, it is said, 
migrate up and down through the bridge pin hole, yet the  same side 
bearing friction is again not enough to pull the string along with it.  
The effect of this side bearing friction appears and dissapears along 
the needs of the argumentation.  Also... and this is the kicker... it is 
clearly demonstratable that strings have migrated some how or another up 
the  pins and slightly away from the bridge cap in cases where there is 
positive bearing at the notch,  (and plenty of it) and positive crown.

Throw in what Dons film seems to depict by the descriptions so far, and 
all the other evidence around and I personally think its time folks stop 
trying to deny the reality of the fact and (assuming there is real 
interest in the matter) start trying to figure out why it happens.

But thats just my take on the matter.

Cheers
RicB

=========================

Hi Ric,

Also, remember that the top of the bridge cap is not
parallel to the soundboard surface.  The edge facing
the speaking length is higher than the edge facing the
back scale.

On Don's film, you can see the first pulse coming
toward the bridge like a Tsunami.  It yanks violently
on the bridge pin and one wonders why the bridge pin
doesn't get pulled out after you play a few loud
notes.

Vladan


============================

#3.  The string under tension will not attempt to
define a straight line across the top of the bridge.
It will be forced in that direction by the bridge
pins.  The string under tension will attempt to define
as exact a fulcrum as it can, and will start exerting
pressure onto the edges of the bridge to do so as soon
as tension is applied.  The reverse of this condition
is that the string being forced flat across the bridge
by the pins will attempt to counter this and part of
that countering is to exert an upward force on the
string on the outside side of each pin. The edges of
the bridge are essentially fulcrum points, and as with
all levers... there is an equal and opposite leverage
exerted on both sides of the fulcrum.

Cheers
RicB