Loose Plate bolts = ?

[Ron Nossaman]

OK, here we go,

>      For tuning stability, the rigidity of the case is a factor, as it
>provides the anchor for the sound board.  Having that laminated case bolted to
>a big piece of iron is going to change the way the case moves in response to
>humidity.  Would not loose bolts allow more movement?  

* Yes they would theoretically allow more movement, but how much case
movement is there with seasonal swings, and would this case movement
necessarily affect tuning stability to a noticeable degree? The floating
plate mount system is not a horizontally rigid mount. There will be enough
spring in the bolts, and give in the wood that they won't effectively
restrain case movements with humidity swings. I'd say a conventionally
bedded system doesn't either because the bedding crushes and you don't get a
positive clamp anyway. Since the floating plate systems aren't any more
rigid a mounting system than a conventional system with less than absolutely
tight lags, and since you can't do anything about it in the floating plate
systems, wouldn't it stand to reason that the floating plate systems
contribute to tuning instability? Have you found that to be the case? I
haven't, nor have I noted any long term improvement in tuning stability by
tightening plate bolts in conventional systems. I think it has very little
to do with anything unless possibly, as Barry said, you are talking about a
full turn of the bolts.   


>     What does string tension do to the case? ........ before removing the
>tension prior to restringing,  tape a length of non-elastic material, ( I like
>1/4" recording tape) from side to side, across the bottom of the piano, making
>it just barely taut.  You may also want to place one across the belly of the
>soundboard. 
>See what happens after the tension is let down!
>Regards, 
>Ed Foote
>

* Well, sure, and taking all the plate bolts out with the piano at pitch
will probably produce some interesting phenomenae too, but it has little to
do with how tightening plate bolts affects tuning stability. Interesting
experiment though, I'll try it next time I tear something down. 

 Ron