Theoretical Action Weight Question (kinda long)

[Bdshull@AOL.COM]

Terry:

<< My question revolves around re-weighing a keyboard.>>

Actually, as you point out, your question involves the entire action.  The 
variations occur all over the place, in the keys, the action;  Sure, improper 
leading should not compensate for gross errors in the action - but you need 
to find these problems and fix what you can, or you will still be 
overcompensating with lead in the keys, and the action will perform poorly - 
with gross variations in down and up weight, as you described earlier.   
Excluding the top action will prevent you from finding important causes of 
touchweight problems related to leverage, such as knuckle placement, hammer 
weight, and although key related - whip foot/capstan placement, and 
irregularities in any of the above, for starters.  Understanding the levers 
in the action, and refining these relationships - Stanwood's articles 
thoroughly cover this, and the archives have plenty to say.  Friction and 
parts weight are important, and understanding the geometry is helpful (the 
coinciding arcs principle - tangenting circles), but you have to analyse the 
action as a lever and understand how to rectify problems you find.  This 
action may have significant leverage problems.  Hopefully, you will find 
these, and you may end up removing some key lead (excess mass/inertia) as 
well.  Stanwood's own method of calculating smooth front weight 
specifications is patented and requires working with one of his licensed 
technicians, but his articles provide the basis for a thorough understanding. 
 Check out these articles in the PTG Journals: "Mastering Friction with the 
Balance Weight System", October 1990, "The New Touchweight Metrology," PTG 
Journal, June 1996, "Standard Protocols of the New Touch Weight Metrology," 
PTG Journal, February 2000, "Through the Eyes of the New Tough Weight 
Metrology Metrology," March 2000.  

Bill Shull
University of Redlands, La Sierra University, 
 
 I have been trying to find a good resource for a description of an effective
 methodology for weighing-off a keyboard. I have had little luck. My
 assumption is that established procedures follow: Get hammers in good shape
 (new or filed, etc.), get all friction components to acceptable levels
 (within a few grams of each other), and regulate the action. Then, with the
 action in place, put your desired gram down weight on the end of the key and
 balance the key with various desirable combinations of key leads. Re-test
 the down weight and up weight to be sure you are where you want to be,
 readjusting the key leads as required.
 
 It seems to me that you would always have a great potential for a several
 gram error that way because of friction variations from note to note (which
 is going to be continually changing), and because of the one or two gram
 error inherent in measuring down weight and up weight.
 
 Is it possible that the following method would yield more consistent
 results?
 
 1) Be sure that excess friction in key bushings is eliminated.
 
 2) Identify several notes at both ends of the keyboard that perform ideally
 (your call) with regard to friction (ideally #1 and #88 - and be sure they
 are properly regulated) by precisely measuring up and down weights.
 
 3) Record the measured up and down weights of these notes (realizing that
 they may be higher or lower than that desired).
 
 4) Remove action stack.
 
 5) Place round tube (plastic or metal pipe about 1" tall) over capstan of
 one of the ideal notes.
 
 6) Set weights upon capstan (actually on tube) such that they exactly
 balance the same down weight (measured in step 3) of that note. Do the same
 procedure for the other notes measured in step 3. These should be
 consistent, varying only with varying hammer weight.
 
 7) We have now accurately replaced the action weight plus an ideal friction
 component with the weights resting upon the capstan. After doing this at
 both ends of the keyboard, a simple mathematical calculation will provide
 the idealized action weights (at the capstan) for all 88 keys (you will need
 to do this process twice - once for the naturals and once for the sharps
 because of differing center rail pin locations causing different key
 leverage components).
 
 8) Remove old key leads and properly plug.
 
 9) Place the idealized action weights on one capstan at a time, place your
 desired down weight at the end of the key, and balance with appropriately
 placed lead key weights (each key lead should be the weight of your intended
 key leads less the weight of the wood plug that will be removed during key
 lead installation). Mark key lead locations.
 
 9) Install new key leads.
 
 Now you have a set of keys that are weighted independently of any variations
 in action friction from note to note (which will always be changing anyway)
 and the small inaccuracy associated with measuring down weight (it seems to
 me that is always an opinion call within perhaps two grams - if you balance
 a nearly frictionless key, you can repeatedly do that to within one gram).
 
 Am I like way out in right field or do these thoughts seem to have any
 merit? Can anyone recommend a resource for an excellent methodology?
 
 Terry (can't blame a guy for thinkin') Farrell
 Piano Tuning & Service
 Tampa, Florida
 mfarrel2@tampabay.rr.com
  >>