[pianotech] problem in mating hammers to strings

[Paul McCloud]

Hi, David:
    I came across the same thing, but mostly in the bass.  It perplexed me until someone on this list explained it.  I think it was Frank Emerson.  The geometry of hammers bored at an angle is very complex, and surprising things happen.  The striking surface of an angled hammer doesn't stay level as it swings.  Straight bored hammers will always stay level.  
    To illustrate, take a small jar in your hand and keep the axis perpendicular to your arm and level to the floor.  If you lift your arm, you'll see that the jar axis will always stay level.  Now angle the jar, and raise your arm.  One end of the jar will be higher than the other as the axis begins to tilt.  
    This may help envisioning why you're having trouble this way.
     Angled hammers must be hung so they are perpendicular to the strings as they contact, not as they rest on the rail.   Perhaps your hammers aren't hung properly..
    I hope this makes some sense.
    Paul McCloud
    San Diego


----- Original Message ----- 
From: 
To: pianotech at ptg.org
Sent: 03/01/2011 6:54:13 PM 
Subject: Re: [pianotech] problem in mating hammers to strings


David

When you say you level the strings, do you use Joe's level, or do you just feel that all the strings are in the same plane?

It really doesn't matter if the strings are perfectly level, as long as the hammer hits all three strings at the same time. That's what you've got to go for, even if the hammer looks uneven. 

Correctly spaced hammers next to each other can travel at an angle, and not touch each other. The best way to check this is to bring the hammer up with a hook, or and see if it comes up straight or at an angle. 

Wim


 



-----Original Message-----
From: David Nereson <da88ve at gmail.com>
To: pianotech <pianotech at ptg.org>
Sent: Tue, Mar 1, 2011 4:40 pm
Subject: [pianotech] problem in mating hammers to strings


I've encountered this several times now with grand pianos.  I 
level strings.  Then for each unison I hold the hammer up 
against the strings by pressing upward on the jack tender, and 
pluck the strings.  The ones that ring aren't being damped by 
the hammer.  The ones that don't ring are being damped, 
indicating (supposedly) that the hammer is "high" under that 
string.  Trouble is, I get the indication that all the hammers 
in the low tenor are high on the right.  Yet when tipping the 
front of the action up and viewing the strike points (which 
appear just above the flange screws from this vantage point), 
they appear straight across.
( _ _ _ _ _ _ _ _ _ _ )
    If I then file the right side of each hammer so that all 3 
strings of each unison are damped equally when holding the 
hammers against them, then look at them again from the front, 
they appear like the teeth of a giant rip saw  (|\  |\  |\  |\ 
|\  |\  |\  |\ , but imagine the line slanting to the right --  
the strike point-- slants only about a third as much as the 
backslash.)  But when I leveled strings, nothing told me that 
the right string of each unison was low, especially not that far 
low.
    This problem doesn't occur in the section with 
non-angle-bored  hammers nor in the capo sections.  So I'm 
wondering if, because of the angled hammers (not in line with 
the shank), the shank flexes when pressing up on the jack, 
causing the hammer to lean to the left, and giving me a false 
indication of how the top of the hammer is shaped.
    I've also had situations when, after spacing hammers, some 
of them still get thrown aside slightly on a hard blow, so that 
one unison string doesn't sound as loudly as the others.  In 
other words, the angle bore or something else is causing the 
hammer to travel or lean on a hard blow.
    --David Nereson, RPT 
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