[pianotech] Bobbling hammers and jack spring pressure?

[Ron Nossaman]

Gregor _ wrote:

> There is no lost motion, check is about 15 mm, aftertouch is okay and I 
> gave some talkum powder to the jack tip and the let off button. The only 
> thing that helped was to set the let off to 10 mm, but that´s not a 
> satisfying solution. The strange thing is that one could play without 
> bobbling hammers but something makes the player stop pressing down the 
> key before the let off point. A very subtile resistance gives the player 
> a hint that the key is pressed down now, but that´s not right. The 
> player could and should press further on. The strange thing is that this 
> problem is new for a few days. I should mention that we had very dry air 
> last weeks and the customer has a floor heating. Therefore I suspect a 
> connection between this problem and the dry air.
> 
> Any comments?
> 
> Gregor

I've seen this happen a lot with new Yamaha verticals in the 
last 30 years. It's just as you describe. The action works 
fine, but the player feels a slight resistance at the bottom 
of the stroke and stops pressing the key before the jack can 
escape. It seems to me to be the design of the jack. The 
leverage ratio of the jack is quite high, and a little 
(normal)  resistance of the jack against the butt feels like a 
greater resistance at the key. Having just picked up the 
damper spring, the added feel of resistance means they stop 
the key stroke before it bottoms out.

In my experience, there are two ways to fix this. The first is 
to try to explain to the player what is happening and impress 
upon them that the action works fine, but they need to learn 
to work it. If they will listen to you, the problem 
miraculously goes away - every single time. The second 
approach is to trash the regulation in whatever way best 
accommodates the idiosyncrasies of the player, so they won't 
have to learn to use it in a functional state. This includes 
weakening damper, jack, and/or hammer return springs, 
increasing let off, increasing key height, shortening blow 
distance, or any other deviation from a well regulated action 
you can think of that fools the operator into thinking it's 
fixed. My preference is that they learn to work it.

The only real problem I've had with Yamaha vertical actions 
through the years is that the capstans tend to be too high, 
floating the hammer shanks off of the rail. For this, I slice 
the rail props and insert a small piece of bushing cloth, no 
glue, to prop the rail up a tad. This takes care of the 
immediate problem, and several years later when the butts pack 
down some, I can pull the shims and touch up the capstan 
adjustment quickly and easily.

My take,
Ron N