[CAUT] knuckles & bobbles

[A440A@aol.com]

Otto writes: 
<< Though there was not noticable friction on the knuckles, I decided to put a

little teflon on them in the form of a dry aeresol spray to speed up

repetition.  >>

   I am not sure of the logic here.  How is reducing the friction at the 
knuckle going to speed up repetition? 
Repetition is dependant first on the height of the backchecking and then the 
speed of the key return, (not the speed of the hammer rising from check, since 
at fast repetiton, the hammer doesn't move up or down until the jack is once 
again under it).  Is the very slight difference in knuckle friction going to 
increase the return speed of the key? 
   To my thinking, greater friction at the knuckle will cause there to be 
more spring strength for the same speed of the hammer rise when released from 
check.  This additional spring strength may be of use in speeding the key's 
return, so reducing it may actually hamper repetition.  There is virtually no 
difference in key return speed between a spring that causes a smooth steady rise 
and a spring that kicks the hammer up fast enough to feel it in the key.   
  If there are bobbles in the hammer, I would look first to let-off, then to 
the interaction of the hammer tail and the backcheck and the friction in the 
grub,(spring slot), and how much aftertouch you are allowing. Many times, I 
have found bobbles when the spring was too strong for the system.  Hammershank, 
as well as balancier pinning is very important in this equation. If they are 
too loose, the spring will be hard to regulate. 
   Going even further, a loose jack pinning will allow the jack to fly back 
and forth uncontrollably, and it may be that repetition will suffer from an out 
of control jack.  Since my eyes are not able to discern such rapid movement, 
this is only a theoretical question. 
regards,

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