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#1125494 - 08/03/04 06:49 PM Re: Lack of crown?
Keith D Kerman Offline
3000 Post Club Member

Registered: 03/12/03
Posts: 3316
Loc: Gaithersburg, MD (Washington D...
 Quote:
Originally posted by Rick Clark:

Del I am curious if the new pianos you are mentioning were Chinese product that may have been overtensioned as described above.

Regards,

Rick Clark [/b]
Del, I am curious as to the actual brand of the piano. I don't think you have written anything here that would offend a manufacturer.
_________________________
Keith D Kerman
PianoCraft
Rebuilding & Sales of vintage and pre-owned Steinway and Mason & Hamlin
New Steingraeber, Estonia, Charles R. Walter, Brodmann, Feurich
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Piano & Music Accessories
#1125495 - 08/03/04 07:11 PM Re: Lack of crown?
Del Offline
5000 Post Club Member

Registered: 09/04/03
Posts: 5246
Loc: Olympia, Washington
 Quote:
Originally posted by BDB:


1] Other variables that might have a bearing would be the metallurgy and heat treatment of the strings, the method of stringing, and the chipping and first tunings.

2] If there is such a difference even in the same make and model of piano, then that means that the variability is beyond the those which could be attributed to design and construction of the soundboard. After all, they all would have had the same design and construction.

3] Perhaps the most important thing that comparisons like this show is that most people don't care enough about the sustain of the tone, at least not enough to demand that it be consistent.
[/b]
1] The quality and consistency of Mapes IG wire is exceptionally good. The strings would receive no heat treatment other than that of the very carefully controlled factory processes. Chipping and first tunings should be fairly consistent within a given manufacturers process. Unless this is done horribly wrong it will have little, if any effect on the tone performance of the piano.

2] The primary difference in this case is the soundboard assembly and how the individual soundboards have responded to essentially identical climate exposure.

3] What can I say. When I visited the same showroom some months after my initial examination two of the three pianos were gone. Guess which one remained.

Del
_________________________
Delwin D Fandrich
Piano Research, Design & Manufacturing Consultant
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Stupidity is a rare condition, ignorance is a common choice. --Anon

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#1125496 - 08/03/04 07:13 PM Re: Lack of crown?
Del Offline
5000 Post Club Member

Registered: 09/04/03
Posts: 5246
Loc: Olympia, Washington
 Quote:
Originally posted by Rick Clark:
Del & All,

I have seen some new Chinese pianos that arrived from the factory 25-35 cents sharp. (However from the same factory others arrived flat, or approx on-pitch.)

A tech will of course realize that it must have been set quite a bit sharper than that before it fell down to +30.

I was really quite concerned if this overtensioning practice was going to have the effect of killing string tone/elasticity or perhaps other deadening effects. Unfortunately circumstances were not such that I could follow the future progress of the pianos.

Del I am curious if the new pianos you are mentioning were Chinese product that may have been overtensioned as described above.

Regards,

Rick Clark [/b]
No, they were not Chinese. They were made in the good old U.S.A.

Del
_________________________
Delwin D Fandrich
Piano Research, Design & Manufacturing Consultant
ddfandrich@gmail.com
(To contact me privately please use this e-mail address.)

Stupidity is a rare condition, ignorance is a common choice. --Anon

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#1125497 - 08/03/04 07:14 PM Re: Lack of crown?
Del Offline
5000 Post Club Member

Registered: 09/04/03
Posts: 5246
Loc: Olympia, Washington
 Quote:
Originally posted by Keith D Kerman:
 Quote:
Originally posted by Rick Clark:

Del I am curious if the new pianos you are mentioning were Chinese product that may have been overtensioned as described above.

Regards,

Rick Clark [/b]
Del, I am curious as to the actual brand of the piano. I don't think you have written anything here that would offend a manufacturer. [/b]
It certainly should.

Del
_________________________
Delwin D Fandrich
Piano Research, Design & Manufacturing Consultant
ddfandrich@gmail.com
(To contact me privately please use this e-mail address.)

Stupidity is a rare condition, ignorance is a common choice. --Anon

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#1125498 - 08/03/04 08:25 PM Re: Lack of crown?
Dan M Offline
500 Post Club Member

Registered: 12/30/03
Posts: 770
Loc: California
In NYC I bet. Compression crowning will give that amount of variability, I've heard \:\)

"“Violence is the last resort of the incompetent.” Isaac Asimov"

Indeed.

Dan

 Quote:
Originally posted by Del:
 Quote:
Originally posted by Rick Clark:
Del & All,

I have seen some new Chinese pianos that arrived from the factory 25-35 cents sharp. (However from the same factory others arrived flat, or approx on-pitch.)

A tech will of course realize that it must have been set quite a bit sharper than that before it fell down to +30.

I was really quite concerned if this overtensioning practice was going to have the effect of killing string tone/elasticity or perhaps other deadening effects. Unfortunately circumstances were not such that I could follow the future progress of the pianos.

Del I am curious if the new pianos you are mentioning were Chinese product that may have been overtensioned as described above.

Regards,

Rick Clark [/b]
No, they were not Chinese. They were made in the good old U.S.A.

Del [/b]
_________________________
The piano is my drug of choice.
Why are you reading this? Go play the piano! Why am I writing this? ARGGG!

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#1125499 - 08/03/04 08:35 PM Re: Lack of crown?
Keith D Kerman Offline
3000 Post Club Member

Registered: 03/12/03
Posts: 3316
Loc: Gaithersburg, MD (Washington D...
 Quote:
Originally posted by Dan M:
In NYC I bet. Compression crowning will give that amount of variability, I've heard \:\)

Dan

[/b]
Well, Del said 7', mapes wire, and made in USA, so that could be M&H, or Steinway. I usually have 5 new BBs set up side by side, and while they do differ a bit in sustain, I have not noted anywhere near the discrepencies Del noted, so I have to assume you are right Dan.
_________________________
Keith D Kerman
PianoCraft
Rebuilding & Sales of vintage and pre-owned Steinway and Mason & Hamlin
New Steingraeber, Estonia, Charles R. Walter, Brodmann, Feurich
www.pianocraft.net
http://www.youtube.com/user/pianocraftchannel/videos

keith@pianocraft.net 888-840-5460

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#1125500 - 08/03/04 08:49 PM Re: Lack of crown?
curry Offline
3000 Post Club Member

Registered: 08/17/02
Posts: 3769
Loc: Hamilton Twp, NJ
It might have been the Baldwin SF that Del is hinting at.
_________________________
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Dampp-Chaser installations, piano appraisals. PTG S.Jersey Chapter 080.
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#1125501 - 08/04/04 12:03 AM Re: Lack of crown?
BDB Offline
Yikes! 10000 Post Club Member

Registered: 06/07/03
Posts: 21444
Loc: Oakland
So if there is one bad sample out of three which did not sell, and it wasn't caught by QC at the factory, either it was damaged in transportation, possibly for climatic reasons, or it was not deemed defective by the manufacturer. In any case, it seems it wasn't thought defective by the dealer.

I actually do doubt that there was a problem manufacturing the wire. After all, that would likely only affect one size, and as I said, everybody changes gauges much too often in the treble.

Defects in design shouldn't result in sample defects. If there was a defect in worksmanship, it is as likely be with the stringing as the belly work. Damage in shipping seems most likely, but it's a mystery to me.
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#1125502 - 08/04/04 07:07 AM Re: Lack of crown?
byebye Offline
1000 Post Club Member

Registered: 02/18/03
Posts: 1426
Three new Baldwin SF-10s in one showroom? Where?

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#1125503 - 08/04/04 08:25 AM Re: Lack of crown?
Del Offline
5000 Post Club Member

Registered: 09/04/03
Posts: 5246
Loc: Olympia, Washington
 Quote:
Originally posted by BDB:
So if there is one bad sample out of three which did not sell, and it wasn't caught by QC at the factory, either it was damaged in transportation, possibly for climatic reasons, or it was not deemed defective by the manufacturer. In any case, it seems it wasn't thought defective by the dealer.

I actually do doubt that there was a problem manufacturing the wire. After all, that would likely only affect one size, and as I said, everybody changes gauges much too often in the treble.

Defects in design shouldn't result in sample defects. If there was a defect in worksmanship, it is as likely be with the stringing as the belly work. Damage in shipping seems most likely, but it's a mystery to me. [/b]
When the problem of abnormally short sustain shows up in a piano that is known to be capable of good sustain the cause is nearly always traceable to changes taking place within the soundboard assembly. Like it or not, wood under constant strain does undergo physical changes. Especially when that stress is predominately compression perpendicular-to-grain. Compression set is a fact of life and can be ignored or dismissed only at our peril.

This is a phenomena that still seems to be poorly understood within our industry even though the wood technology governing it has been well understood and quantified for decades.

As to whether this is a design issue, a construction issue or a materials issue is moot. The three are tightly interrelated. Personally, I am skeptical of any design feature that regularly places any material at levels of stress and/or strain at levels beyond its physical capacity. Unless, of course, you are preparing a car for the Indy 500 and expect it to fall apart after 500 miles.

Del
_________________________
Delwin D Fandrich
Piano Research, Design & Manufacturing Consultant
ddfandrich@gmail.com
(To contact me privately please use this e-mail address.)

Stupidity is a rare condition, ignorance is a common choice. --Anon

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#1125504 - 08/04/04 08:54 AM Re: Lack of crown?
Rick Clark Offline
1000 Post Club Member

Registered: 01/04/03
Posts: 1810
Loc: North County San Diego CA
Del,

I suspect what you call "compression set" is what wood technologists call "stress related deformation" (SRD). I have suspected this (SRD) to have something to do with tone deterioration in old pianos from stressful climates, and of course it hurts pianos in many mechanical ways as well.

This is the first I have read the same SRD might occur in new sound boards. It's an interesting subject and it would be great if someone really gets a handle on it and can get the rest of the industry acting on the knowledge.

What is the "design feature" you are writing about that is overstressing sounbdboards?

Regards,

Rick Clark
_________________________
Rick Clark

Piano tuner-technician

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#1125505 - 08/04/04 12:56 PM Re: Lack of crown?
Del Offline
5000 Post Club Member

Registered: 09/04/03
Posts: 5246
Loc: Olympia, Washington
 Quote:
Originally posted by Rick Clark:
Del,

I suspect what you call "compression set" is what wood technologists call "stress related deformation" (SRD). I have suspected this (SRD) to have something to do with tone deterioration in old pianos from stressful climates, and of course it hurts pianos in many mechanical ways as well.

This is the first I have read the same SRD might occur in new sound boards. It's an interesting subject and it would be great if someone really gets a handle on it and can get the rest of the industry acting on the knowledge.

What is the "design feature" you are writing about that is overstressing sounbdboards?

Regards,

Rick Clark [/b]
Wood technologists call compression set, well, compression set. It is the result of stress related deformation. This latter phase can also be applied to tension deformation. This is the term used primarily by R. Bruce Hoadley in his book, Understanding Wood.

The USDA Forest Service’s Wood Handbook deals more with the concept of ‘creep.’ When a stress is applied to wood it deforms elastically. In the case of the compression-crowned soundboard panel it creates its own load as it expands by taking on moisture after being ribbed. If this load is maintained (as it is in the compression-crowned soundboard panel) additional time-dependent deformation occurs. This is called creep. It occurs even at very low stresses, particularly when those stresses are perpendicular-to-grain compressive stresses.

If a constant deformation is imposed and maintained on the wood member (in this case, the soundboard panel) the initial stress relaxes at a decreasing rate to about 60% to 70% of its original value within a few months. This is called ‘stress-relaxation,’ or compression set. This stress relaxation continues until some equilibrium is reached and there is no longer enough compression stress to matter. Obviously, if the soundboard system was relying on this compression to form and maintain crown there is going to be a problem.

In general, wood can sustain perpendicular-to-grain compression levels up to about 1% without instantaneous wood fiber failure. Above this and the wood fibers begin to deform quickly and often catastrophically. The typical compressive stress levels within a compression-crown soundboard panel can start as high as 1.5% to 2.0%. This level of compression drops rather rapidly as compression stress takes its toll. Along with it goes some of the crown that was initially built into the system. The rate at which the compression level drops is dependent on a number of factors, including:
— The strength characteristics of the specific wood samples.
— The specific amount of initial compression.
— The range of temperature and, more importantly, humidity the wood sample is exposed to.
— The peak level of compression realized during the highest humidity peaks.

Obviously, there are a number of variables and a system has evolved which works reasonably well most of the time. I suspect, however, it has worked some better in the past as we chewed our way through those wonderful old Sitka spruce giants that were able to grow to enormous heights and impressive ages within the protected confines of the old-growth temperate rain forests. Most of which are now history. Such wood is becoming increasingly rare and we are now working on what is left. And what is left would have been rejected out of hand even as recently as half a century back. Times change.

Del
_________________________
Delwin D Fandrich
Piano Research, Design & Manufacturing Consultant
ddfandrich@gmail.com
(To contact me privately please use this e-mail address.)

Stupidity is a rare condition, ignorance is a common choice. --Anon

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#1125506 - 08/05/04 12:35 AM Re: Lack of crown?
BDB Offline
Yikes! 10000 Post Club Member

Registered: 06/07/03
Posts: 21444
Loc: Oakland
 Quote:
In general, wood can sustain perpendicular-to-grain compression levels up to about 1% without instantaneous wood fiber failure. Above this and the wood fibers begin to deform quickly and often catastrophically. The typical compressive stress levels within a compression-crown soundboard panel can start as high as 1.5% to 2.0%.
If a soundboard is 1 meter wide, 1% compression would be squashing from side to side until it is 1 cm. narrower. That's quite a bit. If that's the difference in width from the top of the soundboard to the bottom, that would make quite a curve in it. How do you figure that much stress?
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#1125507 - 08/05/04 09:26 AM Re: Lack of crown?
Del Offline
5000 Post Club Member

Registered: 09/04/03
Posts: 5246
Loc: Olympia, Washington
 Quote:
Originally posted by BDB:
 Quote:
In general, wood can sustain perpendicular-to-grain compression levels up to about 1% without instantaneous wood fiber failure. Above this and the wood fibers begin to deform quickly and often catastrophically. The typical compressive stress levels within a compression-crown soundboard panel can start as high as 1.5% to 2.0%.
If a soundboard is 1 meter wide, 1% compression would be squashing from side to side until it is 1 cm. narrower. That's quite a bit. If that's the difference in width from the top of the soundboard to the bottom, that would make quite a curve in it. How do you figure that much stress? [/b]
But not exceptional. I once took an unribbed Baldwin 743/5 (the designation for the Hamilton back assembly) soundboard panel and drew a line across it diagonally (perpendicular to grain), dried it down to 4.0% MC (as weighed and compared to an oven-dry sample), placed two marks on it exactly 60” apart and left it to sit in the Trumann, Arkansas plant warehouse for 48 hours (during August). It took about that long for the marks to be just shy of 61.2” apart. That’s an expansion of about 2%. Just about what the books predict.

Putting the same panel back in the conditioning room soon brought it back to 4% MC at which point it was taken to the rib press and immediately ribbed (with flat ribs). Once the glue was dry it was taken back to the warehouse and allowed to reach equilibrium. I don’t recall the exact distance between the two marks but it was something like 60.2” and the assembly was highly crowned. This soundboard assembly was allowed to sit, undisturbed, in that same warehouse for a year. At the end of this year the crown was down to about three-quarters of the original amount (with similar temperature and humidity readings in the warehouse). Even without being glued to a back assembly and held down by any string bearing the soundboard panels internal compression was dissipating.

While this was not the most scientific of tests it was still a graphic illustration of the process and what happens to the wood as a consequence.

Del
_________________________
Delwin D Fandrich
Piano Research, Design & Manufacturing Consultant
ddfandrich@gmail.com
(To contact me privately please use this e-mail address.)

Stupidity is a rare condition, ignorance is a common choice. --Anon

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#1125508 - 08/05/04 09:43 PM Re: Lack of crown?
BDB Offline
Yikes! 10000 Post Club Member

Registered: 06/07/03
Posts: 21444
Loc: Oakland
However, the stress in a soundboard that wants to be 61.2" wide when it is being held at 60" doesn't depend on how the soundboard is crowned. That is a result of gluing ribs across its grain, no matter how the soundboard is formed. It is how compression ridges get formed.
_________________________
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#1125509 - 08/05/04 11:56 PM Re: Lack of crown?
Del Offline
5000 Post Club Member

Registered: 09/04/03
Posts: 5246
Loc: Olympia, Washington
 Quote:
Originally posted by BDB:
However, the stress in a soundboard that wants to be 61.2" wide when it is being held at 60" doesn't depend on how the soundboard is crowned. That is a result of gluing ribs across its grain, no matter how the soundboard is formed. It is how compression ridges get formed. [/b]
I'm not sure I understand your point here. The only reason for taking a soundboard panel down to 4.0% MC at ribbing is so that it will subsequently form the crown that results from the resultant stress interface between the (now-compressed) soundboard panel and the ribs. A high level of internal compression is necessary both to form and maintain this crown and that is (usually) how it is developed. That is how the design works and that is why they are called 'compression-crowned' soundboards.

If the soundboard system crown is formed by machining the requisite curve into the rib it is not necessary to reduce the panel’s MC to 4.0%. The system is designed such that there will be little or no internal compression during normal climatic conditions. In general, internal compression is considered to be counterproductive and the system is designed to reduce it as much as possible. We control the MC of our both our soundboard panels and our ribs to between 6.5% and 7% MC as the ribs are glued on. This figure is fairly typical for most rib-crowned soundboard designs.

Del
_________________________
Delwin D Fandrich
Piano Research, Design & Manufacturing Consultant
ddfandrich@gmail.com
(To contact me privately please use this e-mail address.)

Stupidity is a rare condition, ignorance is a common choice. --Anon

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#1125510 - 08/06/04 08:46 AM Re: Lack of crown?
Rick Clark Offline
1000 Post Club Member

Registered: 01/04/03
Posts: 1810
Loc: North County San Diego CA
Del,

I appreciate your writings on this. You know from past threads I have a skeptical thought process so I may probe your assertions or bring up a counterpoint sometimes, but please don't mistake that for criticism. Mostly I'm just trying to get a grasp on these things myself.

Regards,

Rick Clark
_________________________
Rick Clark

Piano tuner-technician

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#1125511 - 05/04/06 04:59 PM Re: Lack of crown?
Stevester Offline
2000 Post Club Member

Registered: 10/04/03
Posts: 2851
Loc: New Jersey
I found this two year old thread in the archives and I thought I would "light it up". There is a lot of good information in the archives.
_________________________
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anon

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