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Topic Options
#640761 - 05/03/06 04:52 PM Petrof touch
Soren Offline
Junior Member

Registered: 06/04/03
Posts: 9
Loc: UK
Anyone out there with practical experience of re-thinking and re-setting up of Petrof grand actions. I am looking at a Petrof from the 1990's with a rather poor touch.

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#640762 - 05/03/06 07:13 PM Re: Petrof touch
BDB Offline
Yikes! 10000 Post Club Member

Registered: 06/07/03
Posts: 22267
Loc: Oakland
First thing on any piano is always to regulate the action as well as you can.
_________________________
Semipro Tech

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#640763 - 05/03/06 07:16 PM Re: Petrof touch
Larry Buck Offline
2000 Post Club Member

Registered: 10/27/04
Posts: 2400
Loc: Lowell MA
The FOUR "R"s

Regulate
Regulate
Regulate

Good Luck
_________________________
"If I have seen further than others, it is by standing upon the shoulders of giants."
Isaac Newton

E. J. Buck & Sons
Lowell MA 01852
978 458 8688
www.ejbuckpiano.com
http://www.facebook.com/EJBuckPerformances

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#640764 - 05/03/06 07:39 PM Re: Petrof touch
Cy Shuster, RPT Offline
3000 Post Club Member

Registered: 12/18/05
Posts: 3448
Loc: Albuquerque, NM
Soren,

What problem are you trying to solve?

--Cy--
_________________________
Cy Shuster, RPT
505-265-4234
www.shusterpiano.com
www.facebook.com/shusterpiano
Albuquerque, New Mexico

Registered Piano Technician
Dampp-Chaser Certified Installer
PianoDisc Certified Service Technician

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#640765 - 05/03/06 10:53 PM Re: Petrof touch
scutch Offline
Full Member

Registered: 05/04/04
Posts: 347
Loc: california
The Petrofs that I have had experience with mainly have problems with factory installation of key leads. They appear to be installed at random but I know there is logic to it.
The action spread can also be adjusted on most Petrofs and sometimes this needs to be corrected as well.
Remove all excess friction first, regulate the action and check your up-down weights. Then make a map of touch weights and key leads and see if you can make any sense out of it. If not then some reorganization may be in order.
Pick your best feeling keys and make note of touch weights and key lead location an number. If this is close to what you want you should have a good idea of what to do next. If not then you should measure your geometry.
Other than that Petrof can be an outstanding piano.

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#640766 - 05/04/06 05:43 AM Re: Petrof touch
Jay Online   content
Full Member

Registered: 07/24/01
Posts: 473
Loc: AUD
About regulation, what do you test in an action and how do you know if is working correctly? For example, you know the piano is not in tune when a note doesn't sound unison.

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#640767 - 05/04/06 05:43 AM Re: Petrof touch
Soren Offline
Junior Member

Registered: 06/04/03
Posts: 9
Loc: UK
Thanks for your replies. I am taking it for granted that the whole action will have to be gone through for friction areas, centering being a key element. Although I have years of experience of practical action rebuilding etc., I have never really had the opportunity to re think the geometry of a particular make of piano action and there is an increasing number of technicians out there who are sharing information on this area. I wish someone would publish a flow chart of steps to be taken after an action has been relieved of unwanted friction and well regulated. Any offers?? Regarding the points raised by Scutch, have the Petrofs you have worked on also had wippen assist springs? This seems to be a further complication when trying to understand the factory designers logic. Have you changed hammers for weight reduction? et. etc.

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#640768 - 05/04/06 07:27 AM Re: Petrof touch
Larry Buck Offline
2000 Post Club Member

Registered: 10/27/04
Posts: 2400
Loc: Lowell MA
Nick Gravagne has been developiong this comprehensive action geometry paper and computer program. It is well well worth the investment.

http://home.att.net/~nickware/
_________________________
"If I have seen further than others, it is by standing upon the shoulders of giants."
Isaac Newton

E. J. Buck & Sons
Lowell MA 01852
978 458 8688
www.ejbuckpiano.com
http://www.facebook.com/EJBuckPerformances

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#640769 - 05/04/06 09:51 AM Re: Petrof touch
curry Offline
3000 Post Club Member

Registered: 08/17/02
Posts: 3770
Loc: Hamilton Twp, NJ
Call Geneva International and have them send you The Grand and Vertical Service Manual and Regulation Procedures. 800 533-2388.
_________________________
G.Fiore "aka-Curry". Tuner-Technician serving the central NJ, S.E. PA area. b214cm@aol.com Concert tuning, Regulation-voicing specialist.
Dampp-Chaser installations, piano appraisals. PTG S.Jersey Chapter 080.
Bösendorfer 214 # 47,299 214-358

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#640770 - 05/04/06 11:57 AM Re: Petrof touch
scutch Offline
Full Member

Registered: 05/04/04
Posts: 347
Loc: california
have the Petrofs you have worked on also had wippen assist springs? This seems to be a further complication when trying to understand the factory designers logic. Have you changed hammers for weight reduction? et. etc.
_________________________________________________
Yes. Just disconnect them to get an idea of their impact on touchweight - not complicated.
I am the type that likes the most massive hammer that I can get away with. I will even add mass to the hammer tails with brass rod in the bass section. Yes I have changed hammers but not for weight reduction. I like Isaacs as they are much more dense than others so the change was for increase in weight. There are limits to this.
Why reduce hammer weight just to satisfy touch weight desires at the expense of tone quality? Normally this is done to avoid solving action geometry problems in my opinion.
The whippen assist spring when engaged will decrease up and downweights. It will allow a heavier hammer.
When the action is regulated and friction on moving parts is correct measure touchweights with and without the springs engaged. You may find that they were used to compensate for an uneven touch across the piano - not very judicious.

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#640771 - 05/04/06 12:44 PM Re: Petrof touch
Roy123 Offline
1000 Post Club Member

Registered: 09/20/04
Posts: 1729
Loc: Massachusetts
Note that heavy hammers will cause high inertia--all the damper springs in the world won't deal with this issue. Unless the action ratio is changed to accommodate the heavy hammers, the action will feel heavy, especially when playing quickly. If the action ratio is changed, the key dip must increase or the hammer travel must be reduced. There's no free lunch!

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#640772 - 05/04/06 07:43 PM Re: Petrof touch
scutch Offline
Full Member

Registered: 05/04/04
Posts: 347
Loc: california
I agree there is no free lunch - getting the best out of a piano is difficult work.
I have never found that heavy hammers contribute to inertia - will disagree there - they just add to the up and downweights.
When I change action spread it is done to correct the problem/s that exist - it has never created a situation where key dip or hammer travel is unusual or excessive. I will also change the position of key capstans, whippen heals and knuckles to get it right.
Many pianos can have lead removed from keys if certain action geometry problems are solved.
This is where the inertia is located.
The actions that I have done will repeat like a machine gun.
A typical example of resulting touchweight from such work could give 40 to 45 grams down and to 35+ grams up - would you call this satisfactory?
What then could be changed to get the touchweight in the 50 down and 30 up range?
Heavier hammers. This is not inertia.
Whippen assist springs if used correctly help with this.
I will admit that heavy hammers will contribute to excessive wear at the hammer flange busgings. Just rebush - the tone is worth it - in my opinion.
I realize that this issue is in conflict with the accepted norm. Many techs will decrease the hammer mass in order to balance an action. I find this distasteful.

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#640773 - 05/04/06 08:51 PM Re: Petrof touch
Soren Offline
Junior Member

Registered: 06/04/03
Posts: 9
Loc: UK
Oh dear! The last two posts are perfect examples of why sincere and skillful technicians become confused and bewildered with the whole business of trying to understand action geometry.

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#640774 - 05/05/06 12:50 PM Re: Petrof touch
Roy123 Offline
1000 Post Club Member

Registered: 09/20/04
Posts: 1729
Loc: Massachusetts
In fact, and I have the math to back it up, hammer mass and action ratio contribute by far the most to action inertia. The effect of these two factors is so large that one can almost ignore any other components.

Just to be clear, inertia in a piano action is felt as an increase in the force to depress a key the faster the key is depressed. No offense to Scutch, but there is simply no debate about this.

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#640775 - 05/05/06 10:49 PM Re: Petrof touch
scutch Offline
Full Member

Registered: 05/04/04
Posts: 347
Loc: california
None taken.
There is inertia in all action parts if you want to look at it that way. Excessive key leads, when removed is most desirable.
That can usually be done when action ratios are corrected, also - key lead is minimal if the ratios are good from the factory.
Lacking math I can say that given the same touchweights I can get suprior performance from an action that has less key lead and more hammer felt.
There is always room for debate.

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#640776 - 05/06/06 12:51 AM Re: Petrof touch
FogVilleLad Offline
4000 Post Club Member

Registered: 03/02/05
Posts: 4683
Loc: San Francisco
Here's an excerpt from an April, 20006 thread in the PTG archives: The short version is that the geometry is really good. It's like 5.2 to 1. Problem is they then over tax the system with a hammer that weighs way too much. ie. Note 4- 12.5 grams note 40.--8.5 grams. Then they compensate with lead & wippen helper springs so they end up having an action that feels like to[o] much intertia. Mostly with the springs. The real fix is to lighten or replace the hammers.

Here's the link to that thread: http://www.ptg.org/pipermail/pianotech/2006-April/subject.html. Scroll down to "Petrof Grands."

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#640777 - 05/06/06 12:35 PM Re: Petrof touch
scutch Offline
Full Member

Registered: 05/04/04
Posts: 347
Loc: california
Thanks for the link. This describes very well the random nature of the Petrof action.
Dale's solution is one solution, not a law of action rebuilding.
I choose to remove key lead and take advantage of the whip helper springs. With excessive key lead I just cannot get the repetition that I want. With too light hammer I just cannot get the tone color that I want.
Agree about the hard hammers - replace is my solution.
12.5g at #4 is huge - probably lots of lacquer, Isaac's are usually 10g and all felt(we are talking about a 6ft piano here). But I will add mass to this if the hammer is not moving the string enough especially in the lo-bass.
I agree that the tone that results from action rebuild can be superior. Petrof has huge potential and the end result is what counts. Does it sing, have great sustain especially in the killer octave(this is more related to the way Petrof installs boards) have great dynamic range in tonal color and volume, have superior repetition and touchweights within a normal range, are the lowest 5 bass notes clear and well defined?If the answer is yes to all then the action was rebuilt very well.

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#640778 - 05/07/06 08:44 AM Re: Petrof touch
Cy Shuster, RPT Offline
3000 Post Club Member

Registered: 12/18/05
Posts: 3448
Loc: Albuquerque, NM
David Stanwood has published most of his helpful formulas on this:

http://www.stanwoodpiano.com

--Cy--
_________________________
Cy Shuster, RPT
505-265-4234
www.shusterpiano.com
www.facebook.com/shusterpiano
Albuquerque, New Mexico

Registered Piano Technician
Dampp-Chaser Certified Installer
PianoDisc Certified Service Technician

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