Lost motion: (was puzzler on M & H BB

[A440A at aol.com]

Conrad  writes:

<<  I agree with the method of setting the wink,('tis how I do it) however I 

> have to disagree with the conclusion that there is no lost motion.

      Small point here, but I never said anything about a wink.  I said that 
I want to feel the jack in contact with the knuckle.  I often feel the 
leather/jack friction without seeing a movement.  




> 

> I believe that the scraping is felt as the _edge_ or corner of the jack 

> rubs as it leave from under the knuckle. As it stands at rest, with the 

> jacktop surface tangent to the knuckle curve, that there is a very small 

> amount of a gap. That little gap (paper thin?) amounts to lost motion 

> and is there for the same reason as that in an upright - to allow the 

> jack to reset for the next stroke. >>

     I don't know about this.  I also don't know how one would measure it.  
However, I can't assume that the knuckle and jack are not in contact by the 
theoretical geometry of the jack's arc, ie. given the resilience of the leather, 
if the distal edge of the jack is aligned with the distal edge of the 
knuckle's core, the  arc of the jack's leading edge will easily compress the  small 
amount of leather that would interfere with the sweep of the jack as it is moved 
out from under the knuckle.  
     There is no need to guess at this, though.  simply block the whippen so 
that it cannot move, and regulate the balancier so that the jack can just be 
felt moving across the leather.  I find that I can do this and not see any 
dropping of the hammer, which suggests that there is no lost motion between the 
two.  
Regards, 

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