[pianotech] Totally glueless

[Terry Farrell]

You're preaching to the choir Ron!  Perhaps it wasn't obvious, but my post was really a string of rhetorical questions - asking why do people believe these things?

Nice explanation though. Thanks!

Terry Farrell

On Jan 30, 2013, at 11:05 PM, Ron Nossaman wrote:

> On 1/30/2013 8:41 PM, Terry Farrell wrote:
>> Good Grief! Common sense?????  I always wonder with polite
>> questioning in my mind when I hear tech talk about transmissions and
>> vibrations shooting this way and that way - along bridges, along
>> ribs, etc., etc.
>> 
>> The theory that "strings move the bridge and the bridge moves the
>> soundboard" is the only thing that makes any sense to me. Why else do
>> we have "vibrations" zinging this way and that, through this
>> structure and that, bla, bla, bla. And then there is conversation
>> about the rim - vibrations reflecting off the rim and back into the
>> field of music (somewhere in the soundboard). What's that all about?
>> I suspect it has some origin in the "sound collector"........
>> 
>> :-(
>> 
>> Terry Farrell
> 
> 
> I've explained this on list three or four times already, but it's something that needs to be looked at realistically, so I'll take yet another pass at the windmill in hopes that someone will get it.
> 
> Look up the speed of sound in maple. you'll find something around 14,000 feet per second along the fiber, and something in the 4000 fps range across grain, give or take depending on grain orientation. Okay, so pick a note, say A-440. In 0.00227 seconds (1/440), the string completes one cycle at the fundamental. In that time, the impulse of the push of the string on the bridge will travel approximately 0.9 feet down through the bridge, which puts it half way to the floor and clear out of the piano before the next cycle even starts. In other words, no vibration, but a slow push followed by a slow pull. Along the bridge, that impulse will travel about 32 feet, which again puts it well outside the piano before the 440 string even completes one cycle. Adjust the frequencies to those found in the bass, and the concept of vibrations in the bridge gets as distant as the numbers generated. Once the initial pulse moves the bridge, the bridge, by moving, moves all the other strings attached to it. It also moves the soundboard, which moves the other bridge and all the rest of the strings. The complexity of the result comes from the interaction of all the moving strings and how they collectively push and pull on the bridge at a huge number of different frequencies, not from little vibrations in the bridge turning corners and reflecting off of glue joints or bouncing around in the bottom of the hole under an un-seated bridge pin. This doesn't make the whole thing predictable in great detail any more than speculating on what the molecules are doing, but I think it's a far more rational description of the basic action.
> 
> People have an absolute genius for complicating anything and everything and feel compelled to invent detailed explanations whether they have any facts or logic to work with or not. It's intuitive, instinctive, and fundamentally irrational. It's also nearly universal. "I've heard", "I was taught", "I believe", "it's obvious", "simply", and "stands to reason" are the enemies. Innate contradictions like the glue joint blocking sound, while a loose joint not passing vibrations because there was no glue with the screws, should be questioned. Bridge laminations must be continuous through the length of the bridge is another one, when it's been demonstrated by people building bridges with discontinuous laminations with no apparent audible penalty.
> 
> That's the bare bones pitch so far, until a more sensible basic explanation comes along.
> 
> Ron N