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Joined: Sep 2018
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For an unbelievable clear singing treble I make ribs that are the proper dimensions for their location and load. Then I adjust the driving point with my asymmetrical rib process. Then the panel is thicknessed to the proper cross sectional shape. Then driving points are rechecked and aligned. Then the bridge cap material i now use is Hickory, and that density is the key, although you will have to perfect your chisel sharpening skills. The string scale is lengthened, and so are the string segments. Then i set the downbearing to 1/2 a degree. The accu- adjust is the best for this, although you can get creative with shimming the aliquots and/or cast string rest.

The rib work i mentioned is primarily weight reduction in nature without compromising strength. Very dense caps stop all internal pin movement(false beats), and lengthened string segments to reduce excess wire stiffness(more volume,clarity and sustain).

-chris


Chernobieff Piano Restorations
"Where Tone is Key"
Lenoir City, Tennessee U.S.A
www.chernobieffpiano.com
grandpianoman@protonmail.com
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Chris,
I would like to hear one sometime. But nowadays my interest is the pianos made before 1900 or so.
This driving point thing you do is interesting.
And what makes me curious enough to react to some of this is that you keep saying all the greats were off in their engineering.

Here's a question???. if the inner rim beveling is on the bent side only, where does that shift the anti node, "towards it? or away from it? "the bent side"

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Hi Blaisguitars,
Driving points (energy distribution areas) in a sense are anti-nodes. And having them done correctly made a large impact on my piano research work. My sense on adjusting panel nodes and anti-nodes is that the impact on piano soundboards would be very negligible due to the piano being a large percussive instrument. On soundboards for violins, guitars, and harpsichords their is much more impact to the tone due to the more intimate nature of the instruments. Since i am getting fantastic results beyond what i could even imagine just two years ago, i think i have traveled down the acoustic path of research as far as i want to go.
Even though i am not endorsing it, Keith Hill's book has some chapters on these types of things that if you don't have it, you may be the perfect candidate for getting it as he goes quite far(albeit too far) into the details.

All the best.
-chris


Chernobieff Piano Restorations
"Where Tone is Key"
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Chris,

Which book? He has several.

Peter Grey Piano Doctor


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Chris,
Yes I like to read up on them things.
A perfect candidate.??? I'll look.
Acoustic path? Yeah.

I don't remember the words node or anti node mentioned before this.

Anti nodes are not driving points! they are the result of wire behavior. "WAVE MOTION"

My god it seems like you are trying to reproduce a loudspeaker. They have a driving point!. (voice coil)

I wish you would answer the questions I ask. I guess you don't know!!!!!.
You really don't think the mounting has any influence in pushing that bubble one way or the other?

And yes there are areas in some soundboard mountings that match the curve to put the stress at neutral, one section is behind the bass end, we've found this to be so, forcing the soundboard down flat there pushes down too much of the crown. Incidentally this would also influence wavelength along the length of the SB Placing optimum response toward the center!

This beveling thing that no one pays any attention is a most serious player in adjusting the SB to be optimum. Let's discuss this a little. It is very interesting. You know the old torch in a dark tunnel.

These boards you make would you say they are diaphragmatic?

We started making guitars 3 years ago now. what an adventure.
R.Blais

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Chris,
I think I mentioned this before, 1881 A1, we did the SB was glued down flat all around, and what a tone they produced! but we just did an 1867 Chickering, and the beveling of the rim, and the grain orientation was what one will find in most pianos made after that time looking at the examples we have here it seems Chickering was very early in this development. Just to say.

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Hi, Peter, search Keith Hills piano book. and a lot comes up. Geeeze.
RB

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Blais,

I suppose i cannot answer your question regarding where the anti-node goes if only one side is beveled. Can anyone??

I truly believe the bridge has to be in the center of amplitude to get the most out of any board. And no one ever did it. The scalloping alone would not be even, nor would the rib dimension be the same cross section across the span.

The diaphragmatic fails completely. It arbitrarily creates a singer central driver away from the bridge. What i do is place the numerous rib drivers directly under the bridge. So my system naturally has much more available energy.

I like your rim angle theories, they make much sense to me. The point you make about the bass section being pushed flat is the very reason i start with downbearing setting there first. That assures the least amount and accurate setting.

I also agree that grain direction has a big effect too. Which is why i always thought it was odd that RC Hybrid boards use a compression crown grain direction. A 90 degree makes sense to optimize compression crowning, but not so much so when the ribs are pre crowned.


Peter,

The title of the book is "Treatise of the true art of making Musical Instruments". Just remember this is NOT an endorsement. Just a couple good paragraphs in a couple chapters is all IMHO. It was one of those books that leave you with more questions than answers.


Chernobieff Piano Restorations
"Where Tone is Key"
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Chris
I never made a SB only re crowned them, that is what we find.

Sometime in the 80's Chris Robinson, Ct. gave a demonstration Re: the behavior of the pulsator on those Steinways and M&H's, and he did this right in our shop, with a wood yardstick and a tuning fork.
Did you ever see this demonstration. It is really cool.
With the tuning fork touching on this stick he could find the anti nodes and nodes and also how the pulsator affected the wave motion. Hmmm.

Yes and the bridge should be placed at the optimum position on the board.
Note! M&H's are unique in this beveling, Gerts beveled the rim all around to meet the SB curve, but the high treble is flat, from where the damper's end and continues along the bent side up to about the first rib, and so did Steinways, and every one we did, "flat mount in high treble".
This shifts the anti nodes to a better place which is darn close to the belly.
The bevel thing is not my theory, it is a discovery.
This moisture expanded SB thing began about 1880 in England it seems, and it wasn't widely accepted until about 1865 or 66'.

I wish you well with your invention. and I;m understanding a little now about your weight reduction theory, and why you need to do it.

Amplitude theory?, why do you think this was never done, maybe it was.

The sand jiggling doesn't reveal everything.

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why you are so focused on first mode of vibration only?

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Me??

There is something pretty cool about the first frequency that causes the sand to move. But, its not an answer all either.

After studying several boards, it quickly became apparent to me one frequency was enough for comparing boards to one another. The most valuable aspect for me was the location were the sand stops up in the treble. The treble sections that are under-engineered will attract the sand. I like the sand to stop before entering the second section. This is verified by examining the rib structure and panel thickness. Another aspect that can be useful, is if the fundamental frequency is still high, then the board is probably worth saving.

You can use the sand as a tool any way you want to, that's just the way i found useful.

-chris


Chernobieff Piano Restorations
"Where Tone is Key"
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Maybe back to the topic. There is a west system 105 epoxy with 206 hardener available in my country, will it be good for this?

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That is what I have used.


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I see that some uv protection is recommended, what did you put on top?
And thank you, you are very helpful!

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The first time I did this, I headed down to our local building supply center and looked for a spray can of some kind of clear finish that specified UV protection on the label. I came home with Rust-Oleum Painter's Touch 2X Ultra Cover Multi-Purpose Paint and Primer in Gloss Clear. Now there's a pile a marketing in a product name!


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Originally Posted by ambrozy
Maybe back to the topic. There is a west system 105 epoxy with 206 hardener available in my country, will it be good for this?


That is also what I used first time around

Peter Grey Piano Doctor


Peter W. Grey, RPT
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www.seacoastpianodoctor.com
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I use 105 with 207 hardener. The 207 is designed to be used as a clear finish.


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I was using the 105 with the 207 hardener myself, but have changed over to System 3 ClearCoat A and B. The West system was too darkly amber for my taste, the ClearCoat is water clear.

Thanks to Peter Grey for the recommendation.


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207 hardener is not in stock at the moment, but if others are using 206 I understand it looks ok-ish, this board is not pretty anyway, so if it is not too dark yellow or too milky then I will be satisfied

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The longer the open time the better


Peter Grey Piano Doctor


Peter W. Grey, RPT
New Hampshire Seacoast
www.seacoastpianodoctor.com
pianodoctor57@gmail.com
https://www.youtube.com/watch?v=PK0T7_I_nV8
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