Spring behaviour

[A440A@aol.com]

Oleg writes:

>I used to worry about the graphite gunk in the balancier slot, but have
>find it to act as a regulator of the spring tension, anyway when not too old.
>As it slows the top of the lever it eventually send more energy towards the
>key , thus helping more repetition that a very slippery spring that will tend
>to push up the hammer too fast.  
>Any idea about it?

Greetings, 
   I don't believe that the increased friction at the top of the spring will 
increase repetition speed.  Under fast repetition, the hammer doesn't rise 
from check before the jack is reset.  Rather, the spring uses the inertia of 
the hammer to increase the speed of the key return.  This necessitates that 
the spring move in the slot,(called the grub at the factory), and any 
friction here will reduce the speed of the spring's work.  
   As friction increases at the grub, the spring may be strengthened to 
compensate, which may put more pressure on the jack to return, but the spring 
doesn't lift the hammer in the time it takes the key to rise far enough to 
allow the jack to reset. (try it,  put a hammer into check and let go of the 
key as rapidly as possible, you will see the hammer drop to rest without 
moving upwards at all. )
   Also, the difference in key return speed between a spring that slowly 
lifts the hammer and one that throws the hammer off the jack is virtually 
nil.  There is no need for a spring to be strong enough to feel the recoil in 
the key upon the hammer's release from check.  An overly strong spring just 
creates wasteful resistance to fine escapment control at pianissimo levels of 
play. It may force the drop to be set too low, creating even more resistance 
during final escapement. It will also create problems with checking, and a 
hammer that isn't checked will cause a much slower key return than one that 
is.  
Regards, 
Ed Foote RPT