Hi, All!

This is primarilly for unknown008. He and I have been planning this type of thread for awhile. However, anyone else is certainly welcome to chime in here!

One of the things that I do, is that I'm a piano tuner/technician. I've heard about vector forces in acoustic pianos. I'd like to have a better understanding as to what they are and how knowing about the use of them might be beneficial in the rebuilding of an acoustic piano.

Thanks!

Here we go again. Trying to explain something. I could do better with pictures.

Vectors have magnitude and direction. They can be represented with lines with an arrow on them.

If you put a 1 lb block on a 45 degree incline. There is the force of gravity acting on the body straight down and there are frictional forces acting on the body. They are different if at rest or if the body is moving.

By drawing the forces, you can solve what the force is action on the block in the 45 degree direction. From that you can determine the acceleration of the block.

To solve these things you can use polar to rectangular conversions and complex number arithmetic and some trig. Initially you learn to solve them visually.

A piano has a force on the string and a force on the hammer for instance.

So, do vector forces have to do mainly with gravity or with the working forces within a machine?

Please know that I'm truly a novice at this sort of stuff! The simpler the terms, the better for me!
Thanks!

Either. A machine example is say the accelerator or brake pedal design. You could analyze the system for any angle of pedal depression.

Gravity can still act on that system, but you may or may not be able to ignore it's contribution.

Fourier analysis can be used to model sound waves when plucking a string. This may be worth your while to look into, but it can become rather complicated.

Or maybe get a scope or some software for an PC audio card that records using a calibrated microphone and can then do an FFT on the audio signal.

FFT of waveIn audio signals - CodeProject

The FFT converts time domain signals to the frequency domain.

e.g. http://www.sigview.com/

I don't know what to say... :o

Since I don't know much about how pianos work, I've done a little search.

This site seems quite good. The images are not large enough though to get the full grasp of what is happening.

Musical Services, Inc. - Piano Types

Oh, this site offers quite a lot to read:

Back check for piano - Patent 7169990

What I can see from the animation from the first site:
- There are moments involved (moments occur when you have long rigid object and a pivot, like a see-saw)
- For the horizontal piano (grand piano) gravity is definitively involved for the hammer to strike the string.
- What drives the hammer is the little 'L' shaped part, which also work on a system of moments.

I don't quite know what to talk about now... maybe someone can add?

What do you mean by rebuilding an acoustic piano? Repairing one which no more works or has defective keys?

If you knew what isn't working, you can easily replace the malfunctioning part I think... It's only my opinion, since I've got no experience with repairing pianos, nor tuning them.

Quote:

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Originally Posted by galactus

Fourier analysis can be used to model sound waves when plucking a string. This may be worth your while to look into, but it can become rather complicated.

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Hi, galactus!

I'm willing to go with trying to understand the analysis, as long as it's put in terms that I can understand.

Thanks!

Quote:

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Originally Posted by Unknown008

I don't know what to say... :o

Since I don't know much about how pianos work, I've done a little search.

This site seems quite good. The images are not large enough though to get the full grasp of what is happening.

Musical Services, Inc. - Piano Types

Oh, this site offers quite a lot to read:

Back check for piano - Patent 7169990

What I can see from the animation from the first site:
- There are moments involved (moments occur when you have long rigid object and a pivot, like a see-saw)
- For the horizontal piano (grand piano) gravity is definitively involved for the hammer to strike the string.
- What drives the hammer is the little 'L' shaped part, which also work on a system of moments.

I don't quite know what to talk about now... maybe someone can add?

What do you mean by rebuilding an acoustic piano? Repairing one which no more works or has defective keys?

If you knew what isn't working, you can easily replace the malfunctioning part I think... It's only my opinion, since I've got no experience with repairing pianos, nor tuning them.

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I know all about acoustic pianos, Unknown008, at least in the physical as well as practical sense. Rebuilding them involves replacing the strings, (piano wires), chipping to pitch, really tuning, replacing felts in the action, regulating and perhaps, refinishing. I've done all of those things a number of times for almost 40 years.

I would like to have more knowledge about the mathematics concerning acoustic pianos though. Something to take me to another level of understanding...

I've read a lot about vector forces, but I just don't understand them. Am looking for just a basic, working knowledge here.

Thanks!

Quote:

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Originally Posted by KeepItSimpleStupid

Or maybe get a scope or some software for an PC audio card that records using a calibrated microphone and can then do an FFT on the audio signal.

FFT of waveIn audio signals - CodeProject

The FFT converts time domain signals to the frequency domain.

e.g. Sigview spectrum analyzer - FFT based signal analysis software

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I will be checking out what's on those sites, K.I.S.S.

What does FFT mean, please?

Thanks!

Fast Fourier Transform

The theory goes as any waveform can be made of any number of sine waves.

Hence you convert amplitude vs time (time domain)

To

Amplitude vs frequency (frequency domain)

This allows you to see the fundamental and the various harmonics of that signal (depressed key on the piano) being generated.

When you check out the site, there is an exaple of a guitar string.