Pin flexing/bending/twisting

[Dave Davis]

David & MicS,

When my mechanical engineer client first brought this up, I found myself answering him based on my experiences and the hearsay that abounds in the piano technician world. Thanks to Ron, Ed, MicS :-) and your responses, it confirmed that my theories are correct, but also that we often don't have controlled laboratory studies to prove our educated theories. 

Dave Davis RPT

p.s.  sorry to bring up the false beat thing again...heh heh.


----- Original Message ----
From: David Skolnik <davidskolnik at optonline.net>
To: Dave Davis <dave at davispiano.com>; Pianotech List <pianotech at ptg.org>
Sent: Monday, November 6, 2006 6:43:25 AM
Subject: Re: Pin flexing/bending/twisting

Dave -
The most difficult aspect of responding to your question(s) is to navigate through the "triggers" that would ultimately derail an otherwise intelligent discussion of a reasonable question(s). Not wanting to point any fingers, I'll just sort of lean in Mic Sprekne's (name misspelled to protect identity) direction.  I thoroughly respect Ric Mic's formidable body of contributions, but, to prove to myself that he's human, I'll occasionally look for something to criticize.  I think the last post in this thread dallied unnecessarily in the danger zone...false beats and round or flat earth controversy!  While it may ultimately be related, there could be so much to talk about before succumbing to the urge for combat.  DOWN! (there's always the midterm elections tomorrow ta quench yr thirst fr blood, matey!)

I write "question(s)" because it IS two questions... tuning pin and pinblock.  This has nothing to do with bridge, bridge pins or false beats, but you would want to be able to distinguish the behavior of the tuning pin, as distinct from the block, in the almost infinite permutations.  I said almost.  For the pins, consider the size, composition, finish, consistency, method of fabrication, more.  The block...material selection, style (glue to wood ratio), drilling techniques, more.  Not to mention tuning pin bushings.

To look for distinctively 'negative' effects seems unnecessarily limiting.  To me, the more interesting draw of your subject is the understanding of tuning pin behavior given a range of variables.  I'm more interested in the impact on the tuning process.  Like, for example, the difference in the internal pin stresses between a piano such as Ed Foote described and one which might have, say, 110 lbs. torque, or less.  How thoroughly do we neutralize the stresses induced in the first instance?  What is the role of flexing/bending (same thing?)/twisting compared to turning in the process of fine tuning?

See - I can't ask just one question either.  Besides - if Ron's committee did conclude that there were negative aspects to tuning, would you change the nature of your business to have your customers pay you for NOT tuning?  Now there's a thought.  Work you can do from home!

David Skolnik
Hastings on Hudson, NY







At 11:23 PM 11/4/2006, you wrote:

Has anyone done a study of the negative effects that occur to a tuning pin or the pinblock while tuning? I service a new-ish 7' Bosendorfer for a Boeing engineer, who is a hobbist with older uprights and we've been discussing the rigors the pin endures while being twisted and flexed, and also the affect on the pinblock.
 
Dave Davis, RPT
Renton, WA
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