Yamaha bobbling

[Isaac OLEG]

Hello,

I've find that the hammer bouncing problem is mostly due to a
synchronization problem between the bottoming of the key and the
checking moment.

The hammer bounce on the jack before the jack have traveled enough to
be out of the way in fact, even if, when moving slowly you can see the
jack out of the leather.
Yes it is a lack of acceleration oàr move at the end of the jack's
path that look like the most probable cause, but also the fact that
the buckskin (ecsaine) groove , making the letoff occurring faster,
the hammer is yet bouncing while the move is in its regulated letoff
moment possibly ?

It occur even when playing normally. Extra heaviness at the end of the
stroke is another problem, , but may certainly add something to the
first.

I'll have to check it out on some instrument to be sure - I know a
good candidate.

Regards.

Isaac OLEG

-----Message d'origine-----
De : caut-bounces@ptg.org [mailto:caut-bounces@ptg.org]De la part de
Richard Brekne
Envoyé : samedi 17 avril 2004 22:16
À : College and University Technicians
Objet : Re: Yamaha bobbling


Hi Ron, and list

Nice points made here, and I can go a long ways down the road to
agreeing with the issue of pressing through lettoff correctly. On both
uprights and grands for that matter.

That said there are several things that can cause a borderline
pianist/piano combination to uncessessarilly suffer from this bobbling
condition that can be easily enough addressed without compromising the
actions power and control. Several of these have already been
mentioned
and many of these easily fall into what most techs would allow for as
<<reasonable, yet not critically PERFECT>> regulation.

Most of that is found looking at what parts are doing what at that
last
2-3 mm of keystroke, and much of the rest of it has to do with
friction
issues.  But I agree that finding real bobbling problems in Yamahas on
a
regular basis is not something I run into often.  Quite the opposite,
I
find Yamahas by and large to be one of the most problem free out of
the
box, most stable long term instruments available.

Cheers
RicB


Ron Nossaman wrote:

> I've never seen this problem in a Yamaha that's being played like a
> piano, but I suppose it's possible. Typically, this has always been
a
> problem with these actions with beginners, kids, and folks with a
very
> tentative touch. To me, it looks like a design thing. The ratio of
> jack length to toe (tender) length is high, so any drag of the jack
at
> the butt translates to increased resistance at the toe, which is
more
> readily felt at the key. As the key is depressed, the pianist picks
up
> resistance from the damper spring first. This isn't far into the
> stroke, isn't out of the ordinary, and is ignored. Near the bottom
of
> the stroke, added resistance is encountered at letoff, when the jack
> toe hits the letoff button, and they quit pushing. When they don't
> push through the letoff resistance and finish the stroke, it makes
the
> hammer bobble because the jack is still under the butt. Assuming the
> action is in reasonable, though not critically PERFECT regulation,
the
> bottom line is that the person playing the piano needs to learn how
to
> work it and the "problem" goes away. Since that isn't likely to
happen
> immediately, I find the quickest and most easily reversible cheap
> trick is to bend the letoff rail brackets down a tad to make that
> letoff about 1/4" - maybe more. That gets the letoff resistance
> farther up in the stroke where they tend to push through it instead
of
> stopping. There will be a point where even the most relentless and
> determined soft paw won't be able to make the hammers bobble. That's
> where to leave it. Feels funny? No power, no control? No sweat. If
> they were capable of power and control, the problem wouldn't have
come
> up in the first place, or at least it wouldn't have been a problem
> unless they are just looking for trouble. Next year, when they've
> learned to work the piano and complain about the lack of power and
> control (or not), these same brackets can be bent back up to get the
> letoff close enough to even it out quickly without having had to
crank
> all the buttons down, then up again. Sure, I hate to compromise a
> functional action to accommodate someone's inability to work it, but
> they aren't going to change until (and if) they change, so all
that's
> left is minimizing the damage until, and if, they do.
>
> These actions work fine, in my opinion, but just aren't the sloppy
and
> infinitely forgiving worn out old spinet or upright action they
> typically replace, and demand some portion of the player's attention
> to adapt to.
>
> For what it's worth, that's my take.
> Ron N
>
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