[CAUT] Keydip--how deep

[Chris Solliday]

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Re: [CAUT] Keydip--how deepRon, if this is a reference to my post =
regarding ratio, I should have been more clear, the relationship is the =
successful marriage of the overall Action Ratio (or StrikeWeight Ratio =
ala Stanwood) to the Hammerweight (again StrikeWeight ala Stanwood). =
Hope this helps. BTW I agree with what you say in general here regarding =
key ratio. I just want to be sure everybody has got apples to apples.  =
Chris Solliday=20
  ----- Original Message -----=20
  From: Overs Pianos=20
  To: College and University Technicians=20
  Sent: Wednesday, October 12, 2005 4:46 PM
  Subject: Re: [CAUT] Keydip--how deep


  Hi Mike and all,


  There have been some good posts on this thread.


    . . .  I don't think any hard-fast rule is going to suffice.
    -Mike Jorgensen


  With the exception of the final jack position relative to the roller, =
I agree.


  The jack position (relative to the roller) at full key dip (with the =
hammer in check) is probably the only hard-fast rule when it comes to =
key dip/hammer blow considerations. Since the hammer/key ratio varies so =
widely, as others have also mentioned, even within the one brand/model =
of instrument, there will need to be an adjustment from the standard =
spec of dip and/or blow in many situations. Increasing the blow distance =
on a high-ratio action will tend to place the already =
ordinary-relationship of the jack roller contact even further away from =
its line of centers. Reducing the blow distance in the case of a low =
ratio action will tend to improve it.


  If the dip is insufficient for a given action ratio, the lack of =
jack/roller clearance at check may cause the action to blubber at =
let-off, particular when played softly. If the dip is set so deep as to =
cause considerable clearance between the jack and roller at check it =
will slow repetition.


  The much mentioned problem of the hammer/key ratio varying so much =
with the US S&S pianos got me thinking about the problem again recently =
when retro-fitting one of my actions to another factory piano (the =
instrument in question seemed to have a plate position problem which was =
accommodated in the original action by fitting the hammers 3 mm short of =
130 mm. When I fitted my action I followed suit and hung the hammers =
short also, since I wanted to keep my action stack at the correct =
position with respect to the keyboard (to preserve the action ratio I =
wanted - 5.7:1). The shorter hammer position will reduce the hammer/key =
ratio, but only by a small amount.


  In the factory situation, if the plate is not positioned according to =
the standard specification, I believe it is inappropriate to shift the =
action stack relative to the keyboard, in an attempt to shift the strike =
position (line). If a piano is built with the plate out of position, it =
should be a simple matter to tolerate a small adjustment in the hammer =
position along the hammer shank. A 3 mm + or - adjustment of a hammer =
from say a standard 130 mm standard distance from the hammer center pin =
will allow for an out-of-position plate to be accommodated without =
turning the action geometry into a disaster.


  If an action stack is moved only 2 mm relative to the keyboard it will =
have a major influence on the hammer/key ratio, which will cause major =
headaches at regulation time (if the regulator is aiming to obtain a =
workable regulation with standard specifications). The truth is we often =
need to bend the specs somewhere, to get real-world actions working at =
their optimum level.


  Ron O.
--=20
OVERS PIANOS - SYDNEY
     Grand Piano Manufacturers
  _______________________

  Web http://overspianos.com.au
  mailto:ron@overspianos.com.au
  _______________________
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