[pianotech] problem in mating hammers to strings

[Shawn Hansen]

Howdy,
Is this happening to you on new hammers when doing an action rebuild?

How does the strike line look when you prop the shanks up so that they are
parallel with the "ground" or key bed?

The shorter the piano, the more flare there is in that tenor section of
strings, making the need for more of an angle in the hammers.  The more
angle in the bore of the hammer, the more that section is tilted towards the
bass so that the length of hammer can pass its neighbors without touching.
 When you hang brand new hammers with a good deal of tilt the right side
will be higher than the left.  It is usually a pretty subtle thing, but a
shaping of the new hammers when the shanks are sitting parallel to your
bench will help remedy that.  In the end though, the strings, when leveled
are your real guide to fitting the hammers.

Shawn

On Tue, Mar 1, 2011 at 8:33 PM, David Nereson <da88ve at gmail.com> wrote:

> 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
>



-- 
Shawn Hansen RPT
certified piano technician
816.896.4047
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