[CAUT] Jack speed, (was Tight balancier

[A440A at aol.com]

Jim writes: 
<< I don't
think I can add much to what has already been said, except for one thing.
I don't remember who said it, or when, but it had to do with pinning the
jack as tightly as the balancier.  I don't agree with that.  You are far
more likely to have repetition problems due to a jack that's too tight than
you are with one that's too lose. >>

Greetings, 
  Um, That was me that said that!  I have found that an action will play just 
as fast with a jack pinned at 6 grams as a jack pinned at zero friction.  The 
jack pinning doesn't seem to interfere with repetition until it passes 8 
grams, and even so, you have to have somebody that can play real fast to create a 
problem.
    A 6 grams, a jack will still move faster than the eye can see.  For heavy 
use pianos, the pinning will loosen up from where it begins, so I have always 
pinned them near 6 grams and never had a problem with repetition speed. The 
jack will move faster than it needs to, even with 6 grams of tension. (Alicia 
de La Roccha played Ravel on a piano I had set up with jacks pinned like this, 
and told the stage manager it was the first time she had ever found a piano 
that needed nothing but tuning.) 
    Many techs think that looser pinning and/or stronger springs will 
increase repetition speed, but I disagree.  Repetition speed depends primarily on how 
fast the key returns and checking height.  The jack reset speed of an a 
spring set to throw the hammer off the balancier will not exceed that of one that 
has a so slow of a hammer rise that it cannot be felt in the key.  If you 
compare return speeds of two adjacent keys, one with a lot of spring, the other 
with much less, you will see that both come up together.  The problems with heavy 
springs are found in pianissimo playing, where the resistance to escapement 
is higher due to the drop button interfering at the last possible moment of 
control.  
    The near instant empirical capacity of this list is such that if we 
wanted, there could be a hundred different techs try the tighter jack pinning and 
publicize their findings in the next couple of days.  I certainly don't think 
everybody should believe what any one of us says!  Try a tighter jack for 
yourself and see if you can play it fast enough to fail, let us know what you find. 
 
Regards,  

Ed Foote RPT 
http://www.uk-piano.org/edfoote/index.html
www.uk-piano.org/edfoote/well_tempered_piano.html