[pianotech] Totally glueless

[Ron Nossaman]

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