Grand Touch

[Ric Brekne]

Hi again Ric

I should like to point out that most of the repliers to your posts operate with Stanwoods measurments and metrology.  If you would like comments more specific to basic touchweight issues then you should provide us with a few more specs.  Front weights and Strike weights of 6 or 7 keys along with their whippen radius weights and key ratios in addition to the up and down weights.

That said... if you do have a 5.5 strikeweight ratio along with the up and down weights you supply along with a more or less usual whippen radius weight of around 19 grams.... the only reason for over excessive key leading would be if Petrof was using gargantuan (or at least very heavy) hammers.  The Petrofs I have seen through the years weigh in well under this catagory and typically have Front weights slightly under Stanwoods recommendations for maximums... tho there is a bit of variance with these instruments. 

I'd guess that if you were to look for a medium Petrof spec... youd find a balance weight of around 38-40 grams as your instrument has, a 5.7ish Stanwood ratio, top medium to mid heavy Strike Weights and Front weights hovering around the max table.... and pretty darn uneven key to key.

Petrofs are often good jobs for the field tech as you can easily improve the touch by evening things out without actually changing the overall configuration.

One other point...  You mention that keys are not binding.  Try doing a few samples of up and down weight measurements with only the keys on the action frame to get key friction levels.  You might be suprised what you find... but again you may have observed quite correctly after all.  Still, if you havent done it... try a few and post your results if you would.  I for one would be interested.

Cheers
RicB

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Hello List,
  It has been fascinating reading the posts on inertia, initially sparked off by my original posting on the Petrof action I am dealing with.  Unfortunately I still don't have any further clarification as to whether inertia is the problem.  I have been back to the piano and checked certain areas which I had not previously been able to do.  If I could reiterate, the situation is:-

  
A Renner action in a 12 year old Petrof concert grand which feels heavy and tiring to pianists.
  The D/W  average is 48g and U/W average 28g. Action ratio around 5.5
  The regulation is not perfect but is good.
  The damper pick up point is right.
  The keys are not binding at the balance point or at the capstan.
  The key weighting goes from 3 half inch weights in the bass through a (curious) tenor octave of 4, then to 2 and 1.  Obviously, the positioning of weights is crucial but without photos I can only describe the positioning as not looking unusual in any way.
  I noticed that the whippens are the Renner design to take a helper spring.  I don't see evidence though, that a set of springs or looped flanges has been removed. They are usually just unhooked if a technician decides against them.

  So, given that friction does not appear to be a problem in the general feel of the action, what would be your next steps in solving the problem.

  ric