[pianotech] ever changing hammer line response

[Roger Jolly]

Hi John,
               Balance rail hole height and excessive friction can 
sure change the hammer line.  Depending on the force of the blow, it 
will change where the hammer comes to rest, as will any other 
inconsistency of friction.
You are correct in your assertion that some evidence in key level 
will be apparent.
Time Tom is observing 1/2" difference in sharps to naturals, this 
will not be the problem.  However I have never seen this kind of 
swing in 35yrs.  The only way that this could happen, is a mobile 
balance rail, or a combination of incorrect key height, and a too 
tightly set up stop rail.
A 1/2" differential tends to indicate several things are out of place 
at the same time.

One remote possibility is the unicorda arm pushing up on the key 
frame with humidity swings.  Graphite the top of the arm, and look 
for some transfer to the bottom of  the key frame.

Regards Roger


At 03:49 PM 02/11/2008, you wrote:
>On Sun, Nov 2, 2008 at 1:49 PM, Paul T Williams 
><<mailto:pwilliams4 at unlnotes.unl.edu>pwilliams4 at unlnotes.unl.edu> wrote:
>
>  Tight balance rail holes can alter lots of things....If they don't 
> always settle down, freely, to the BR punchings, your hammer line 
> will indeed be off...Slightly lift your keys and see if they fall 
> right back...if sluggish, then there's a problem.
>
>
>
>I'm certainly no expert, and am merely repeating what is taught in 
>Yamaha's 37 Steps.
>
>The balance hole, according to Yamaha, should be tight enough so 
>that when the key is lifted about 10 mm, it does not return on its own.
>
>If the BR holes are too tight, how do they work themselves up a BR 
>pin?  I'm trying to visualize how that would happen when there is 
>the return force on the capstan from the whippen, the lead in the 
>front part of the key, the key stop rail in proper position, and the 
>BR pins angled slightly backward.  I'm not disputing here -- just 
>trying to learn some more.
>
>Plus, wouldn't you also see obviously unlevel keys in such a case? 
>And would it cause uneven hammer line of the 1/2 inch that Tom mentioned?
>
>--
>JF
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