[CAUT] tight balancier - defining bobble

[Willem Blees]

Quoting David Ilvedson <ilvey at sbcglobal.net>:

> Maybe Wim could send a photo...?
> 
> David Ilvedson, RPT
> Pacifica, CA  94044
> 

Sorry, I don't "do" digital photos. Too much trouble for this camera 
neophite

Wim  


> ----- Original message ----------------------------------------
> From: RicB <ricb at pianostemmer.no>
> To: caut at ptg.org
> Received: 11/14/2006 4:32:31 AM
> Subject: [CAUT]  tight balancier - defining bobble
> 
> 
> >Hi again Wim
> 
> >One thing is for sure.  If your hammers are not even touching the
> check 
> >on medium to light blows... then the field is narrowed quite a bit.
> What 
> >happens when you just push the keys through aftertouch without
> enough 
> >force to let the hammers actually hit the string ?  I dont mean like
> an 
> >aftertouch check. Use as much force as you can without letting the 
> >hammers make contact with the strings.  One test I ran into for 
> >rep-spring strength a while back went along these lines.  The
> rep-spring 
> >should be just tight enough so as to prevent the hammers from
> checking 
> >with this kind of test... but no stronger. You should see the
> hammers 
> >dipping say about 8-10 mm before springing back up to drop position.
>  
> >They should dip more then drop but less then check.
> 
> >If you arent getting any of this kind of action then the rep-spring
> is 
> >too tight for whatever other conditions you have. Tight hammer
> centers 
> >will slow things down for example so a certain combination of these
> / 
> >tight balancier pins and strong rep springs could cause your
> trouble.  
> >Even if each of the individual parameters seem ok when checked 
> >by-themselves.  Point is... if the tails are not even hitting the 
> >checks.. then it cant be really much of anything else.  At least not
> 
> >unless something else is ridiculously out of wack. 
> 
> >What else could cause the hammers to hang up so much that hammers
> wont 
> >even touch the checks ?... Hmmm... I suppose a lot of rather strange
> 
> >stuff could get into the picture... but I cant think of anything 
> >reasonable off hand.  Perhaps a very strong jack spring with minimal
> 
> >knuckle clearance could contribute.. ? I dunno..  what kind of
> strange 
> >tail arc and check angle could cause what you describe below ?
> 
> >In any case seems to me you want to make sure whether the tails are
> 
> >actually making contact with the checks or not at this point. Maybe
> mark 
> >a few of the worst offenders with a bit of chalk on their tails and
> see 
> >if it rubs off on the checks ?
> 
> >You really got an interesting thread rolling in any case there Wim.
> 
> >Cheers
> >RicB
> 
> 
> >     > Hi Wim
> >     >
> >     > Are they actually bouncing off the checks ?  Or are they
> simply
> >     > hitting
> >     > the rep lever and getting sprung back up before they even
> touch the
> >     > check ?
> >     >
> >     > Cheers
> >     > RicB
> 
> >    It's hard to tell. I beleive they don't even make contact with
> the
> >    check, but I've had notes that even on a medium hard blow, much
> less a
> >    hard blow, where the hammer doesn't check. It acts like it is
> not even
> >    touching the check, but it goes down far enough where the it
> should be
> >    hitting the check. But if I move the check forward, the tail
> hits it
> >    on the way up.
> 
> >    Wim
> 


Willem Blees, RPT
Piano Tuner/Technician
School of Music
University of Alabama
Tuscaloosa, AL USA