Dithering Hammers

[Avery Todd]

>Alan,
>
>I haven't seen this mentioned yet, so I thought I would. I don't know if 
>it's the "correct"
>answer or not but......
>
>I'm assuming you've established that the dip/key height is correct? If you 
>don't have
>enough dip/aftertouch, you will definitely have "dithering" hammers (I 
>love that term!)!
>
>At full dip, the jacks HAVE to have escaped enough to be in front of the 
>hammer butt!
>If not, they will definitely "dither" on the hammer butts on a soft, maybe 
>even a medium,
>blow.
>
>I believe some people (Yamaha?) says that the jacks should be about half way
>between the butt and the catcher at full dip!
>
>I don't know if this will help or not but I thought it would be worth a post!
>
>Avery
>>A message I tried to send a few weeks ago!
>>
>>
>>
>>Hi guys,
>>I am Alan and have been servicing pianos in Edinburgh for the last 10 years
>>with also a previous short stint in Southern Africa.
>>
>>I too have been baffled by the problem of dithering hammers in Yamaha
>>uprights (brand new) after re-regulating the set-off to 1/8". It seems to me
>>that the factory set the set off wider than usual to accommodate the muffler
>>rail so that the hammers would not block when the muffler rail was in the
>>down position. However, with the set-off being 1/4", without the muffler
>>rail (practise pedal) in use, does not give the piano a very dynamic touch
>>i.e. you cannot play very loud, and above all you cannot play very soft!
>>which is what "piano" is. The closer the set-off to the string the more
>>dynamic control the player has . Set- off is the point at which the jack
>>disengages from the butt and from then on the player has no control over the
>>hammer.
>>
>>If the set-off is too far away you have less control from the moment of
>>escapement. Now in most actions if you regulate to 1/8" set-off and even
>>less in the treble, (I'm talking upright actions here) and all the other
>>measurements are left standard, the action works fine. But on some actions
>>this just does not happen as with Yamaha. Playing loud is fine, but as soon
>>as you play very softly, the hammer dithers.
>>Now this hammer dither is caused by the butt bouncing off the jack before
>>the hammer has had a chance to go in to check, and not by the balance hammer
>>bouncing off the check
>>
>>  You mentioned a design problem, but just exactly where is the design
>>different from other actions? The only design feature I can think of is that
>>the length of the jack is too short. In other words there is not enough
>>leverage on the jack by the set-off button. If the jack were longer, the tip
>>of the jack would move much faster away from the butt during the aftertouch
>>motion. The jack must get out of the way faster than the hammer bounces off
>>the string! So to cure the problem is problematic; one can't obviously
>>lengthen the jack, but you might be able to increase the leverage on the
>>jack. I have tried moving the set-off rail closer to the jacks themselves
>>but this only seems to make a very slight difference. Changing the tension
>>of the butt springs does not solve the problem either. The only reasonable
>>solution I have found is to adjust the check distance much closer to the
>>strings. But then this becomes a non standard measurement, 1/4" instead of
>>1/2".
>>
>>Of course all this begs the question; How softly is a piano supposed to
>>play? I have had many years experience playing piano in restaurants and
>>believe me, if there is a table right next to the piano, you have to play
>>VERY SOFTLY.
>>
>>I sure hope one of you out there has not just a solution, but the correct
>>solution. This has been bugging me for years.
>>
>>Best regards
>>Alan Forsyth
>>
>>_______________________________________________
>>pianotech list info: 
>><https://www.moypiano.com/resources/#archives>http://www.ptg.org/mailman/ 
>>listinfo/pianotech
>>
>>
>>     I don't think you can expect to play quite as softly as a 
>> well-regulated grand, but almost.  When I used to complain about this to 
>> the tech. folks at Yamaha in Buena Park, they would say to check the 
>> same things listed in Carman Gentile's reply, including the pinning, the 
>> latter being an item you might not expect to be a contributor to the 
>> problem.  Any hesitation in the key stroke, which might be partly caused 
>> by a tight key bushing, could contribute to the tendency to dither, or 
>> "bobble".  So you might take the action out, and tap with quick 
>> repetition on the rear end of the keys and see that they all return with 
>> no sluggishness.  Maybe allow the key dip to be slightly larger than normal.
>>     Regarding let-off, if I'm not mistaken, the Yamaha uprights that 
>> have a Disklavier with the "Silent Piano" feature have let-off at almost 
>> 1/2" !   Maybe it's only 1/4".   I first heard of this at a Disklavier 
>> servicing seminar given by  LaRoy Edwards at a Yamaha dealer's store.  I 
>> believe he was claiming that it didn't affect the playablility of the 
>> piano all that much, which seems doubtful.  I didn't play the piano, but 
>> the Disklavier mechanism played it at what I would call a pp level, 
>> maybe even ppp.  So maybe let-off can be a bit wide.  Don't know what 
>> else to suggest, except call Yamaha and see if they have anything new on 
>> the subject.  --David Nereson, RPT, Denver