[CAUT] tight balancier - defining bobble

[David Ilvedson]

Maybe Wim could send a photo...?

David Ilvedson, RPT
Pacifica, CA  94044


----- 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