Seasonal pitch change:

[RicB]

Hi Don

A couple things to remember... these are all based on same size wire  
0.9 mm (seemed like a good average) and short back lengths.  Still they 
give a good enough picture.  Longer back lengths end up requiring even 
larger deflection changes for any given pitch change, but downbearing 
levels are lowered.  Still... no soundboard/bridge is going to rise 5 + 
mm me thinks.  

I am also curious as to why damppchasers have an obvious positive 
affect.  Obviously wood is involved.  In grands however... I cant see 
the bridge itself being to awfully much affected by the DC unit (perhaps 
I am wrong).  And the bridge is where most of my attention is focused on 
this issue at the moment, for a couple 3-4 reasons as I've stated in 
other posts.

Rim, pinblock, and frame could all conspire to alter the end points 
somewhat.  I still dont quite get why this should effect the lowest 
tenor strings sooooo much more then others.

btw... it always seems to me like there are 4 independent sections and 
they all respond pretty similarly to each other.  Pitch drops most in 
the lowest notes of each section.   The bass and top sections behave a 
little differently then the middle to... but not all that much.  That 
points me back to the bridge..... grin.

Cheers
RicB


    Hi Ric,

    Most interesting figures. I've not believed soundboard moving up and
    down
    had much to do with pitch corrections for some years.

    What I *do not* understand is *why* damppchasers work to ameliorate
    seasonal pitch change. Clearly they don't have much effect on metal.
    That
    leaves the rim and the main frame as possibilities.