[pianotech] problem mating hammers to strings

[Joseph Garrett]

David N. Said: 
"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,
Hmmmm? Have you ever hung a set of grand hammers? If so, then you should know that the whole process needs to be thought of in a 3 dimensional perspective. If the angled hammers are hung at true vertical, oft-times the tails will drag on it's neighbor and the shoulders will bind on the opposite neighbor. To avoid this the hammers are actually hung with a slight tilt. What you are observing, IMO, is that "tilt". Put a flat board under the tails and check, with square,  to see if the hammers are exactly at Vertical or some degrees off. If they're off, then that would produce the problem you are perceiving. OR...there is a situation with some grands, where the agraffes are consistantly off, because of the angle of the overstringing and way they were seated. That is not as common, but I have seen it. (or, at least, I thought I did.<G>)

Regards,
Joe



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Joe Garrett, R.P.T.
Captain of the Tool Police
Squares R I
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