Bass hammer checking

[David Skolnik]

Phil-

Hammer checking and springs are especially subject to change going from 
"lap to gap", due to the flex in the keyframe.  Actually, the other 
regulating steps would also be affected except these are the two most 
lap-friendly steps.  I think Ron Koval was  correct in suggesting that it 
is probably discrepancy.   In other responses, Kevin Ramsey suggested 
finding a balance point to do the regulation on your lap, but I think this 
is unreliable.  Joe Garret's point re: frame bedding  is good, especially 
since it's easy to be careless about the bass bolt (if there is one). Roger 
Jolly made all the points I was about to in my response.  I would only add 
that a short tail will make it impossible to achieve the regulation spec he 
mentions (shank center line), and that the actual tail profile is dependent 
upon the shape of the back check.  "Grooving" the tail sometimes doesn't 
work as well as removing any glazing that has built up on the wood., and if 
you are describing having to "roughen" the backcheck leather, there may be 
no nap left, indicating the need for new leather.

Regarding the "phantom checking",  you said you weakened the springs.  If 
the dip is deep enough to jam the jacks, It could be that the friction of 
the back (or is it front) of the jack against the rep lever felt block (#38 
on Steinway diagram), especially with weakened springs.

I know you'll figure it out soon.

David Skolnik


>Hi Phil,
>              Your problem is probably poor tail arc, and or check Rake, 
> (angle)   The radius of the tail needs to be 2 1/2" radius, and square 
> with the hammer rail. Back check angle about 22 degrees back from 
> vertical. And the check height needs to have the centre line of the 
> shank, at the top one third line of the check at rest with the correct 
> blow distance set.  1 7/8" approx.
>Hope this helps.
>Roger





At 06:45 PM 03/14/2002 +0000, you wrote:
>Yesterday I worked on an older Baldwin with a Schwander action that
>had a characteristic that I've encountered on other grand pianos,
>some having it more than others.  The hammers check perfectly on the
>bench or when the action is pulled out in your lap, but won't check when
>the action is in the piano.  This behavior is usually only noticeable in the
>low end of the scale and becomes most pronounced at the bottom.  On some
>pianos it seems that you can't get the hammers at the bottom end to truly
>check no matter what you do; make the checking shallower, make it deeper,
>groove the tail, rough up the check leather, change the back check angle,
>reduce rep spring strength to almost nothing, etc.  When I say 'truly check'
>I mean behave as in the rest of the piano.  The hammer is held
>some distance below the string when the key is down and rises
>when the key is released.  Apparently some sort of 'checking'
>is going on because even on a hard blow the hammers don't bounce back to
>the strings.  But the tail isn't really being held by the backcheck when the
>key is down.  What's the reason for this?
>
>Phil F
>---
>Phillip Ford
>Piano Service & Restoration
>1777 Yosemite Ave - 215
>San Francisco, CA  94124
>
>
>
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