[pianotech] Grams, swings and centre pin sizes [was Kawai parts - response]

Ron Nossaman rnossaman at cox.net
Thu Jan 8 13:46:12 PST 2009


V T wrote:
> Hi Ron,
> 
> Interesting that you put the tight ones in the treble! The
> opposite of what I am doing. I will do some experiments,
> although, as you say, if the action is within an acceptable
> range, it would be very hard for the player to know.
> 
> I am curious as to why you see more need for a tight center
> in the treble. 

I used to put the tight ones in the bass too. Then I got to 
thinking (uh-oh) how repinning a relatively loose treble can 
improve the tone. I also considered that, when setting up an 
action with new parts, the problematic part was the bass. If I 
could get the bass to work, the rest was not a problem. So I 
tried it, didn't notice any particular problems, and have been 
doing it like that since.


>My thinking is that hammers that are angled
> and heavy will twist the shanks the hardes. The angle of
> the hammer creates a difference in load for the two sides
> of the bearing (left side center-of-mass is not at the same
> radius as the right side).

I'm not so sure it works that way, since the two sides are 
connected. Even so, the forces put on the flange bushing can't 
be higher than those put on the bottom half of the bushing by 
the jack shoving a heavy hammer up toward the string at over a 
5:1 leverage ratio, can they?


> The one thing I have noticed is that loose centers in the
> bass make the action feel like a shot gun with a light
> trigger; it's more difficult to control the low dynamic
> playing levels.
> 
> Vladan

I've noticed something like that too, when everything's loose. 
A tighter pinning of the rep lever helps that.
Ron N



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