hammer "throw" on hard blow

[Marcel Carey]

Dave,

I had not caught that you were talking about uprights. I've seen this
problem often (Hamiltons and a few others). The problem also happened
in the treble so I don't think the hammer boring is at fault. I've
noticed that the shanks were not aligned with the hammer butt. It's
the way the hammers are hanged. They install the butts and then glue
the hammer shanks with the hammers already glued. They usually do this
in the piano and align the hammers to the strings. If you align your
eyesight with the middle of the action you will probably notice that
there is an angle at the butt-shank joint. This is why hammershanks
are files(tapered) in the bottom so the side angle can be adjusted to
mate the strings. This makes OK for string mating, but on hard blow it
clearly make the hammers wobble.

Have a good look and let us know if this applies to your problem
pianos.

Marcel Carey, RPT
Sherbrooke, QC

> -----Original Message-----
> From: pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org]On
> Behalf Of David Nereson
> Sent: September 2, 2005 2:43 AM
> To: Pianotech
> Subject: Re: hammer "throw" on hard blow
>
>
> V T wrote:
>
> >Hi David,
> >
> >When hammers are bored, it's really important to drill
> >the hole so it passes right through the vertical
> >center line of the moulding.  (This imaginary line is
> >inside the moulding.)  The desired effect is to
> >ditribute the mass of the hammer about evenly on both
> >sides of the hammer shank.  I often see hammers that
> >are not bored very accurately and the heavier the
> >hammer, the worse the problem will be.
> >
> >This too is an approximate solution to the problem.
> >On bass hammers where you might have, say, 15 degrees
> >of angle on the hammer relative to the shank, the
> >weight on one side of the hammer will be closer to the
> >action center than the weight on the other side.  That
> >really isn't balanced either.  However, you can see
> >that the problem could be quite serious on a heavy
> >bass hammer that has been drilled off center, and in
> >such a manner that the side that has its mass further
> >from the action center is also further from the shank.
> >
> >In that case, you have an unbalanced mass that is
> >about 5" away from the center pin, so that can cause
> >quite a distoring force on the bushing and the shank.
> >
> >Hope that applies to the problem on hand.
> >
> >Vladan
> >
> >
> >
>  Yes -- I hadn't considered the hammer being bored
> off-center.  I kept
> checking the hammer-to-string mating, and it seemed OK --
> i.e., when
> held against strings by pushing on the butt (not the hammer
> tail), then
> plucking the strings, none of them "ring" longer than the
> others.  I
> encounter these "shaking", or wobbling hammers a lot on the
> Hamilton
> studios, and some Yamaha studios and uprights, especially
> in the very
> low tenor, where they have a few shanks longer than the rest of the
> tenor section.  But when there's a lot of them, I can't
> imagine they're
> all bored off-center.  If they are, it's not by much (I
> haven't miked
> them), but maybe it doesn't take much.
>     I checked the pinning very carefully since that was the
> most likely
> suspect.  I purposely re-pinned the thing very tight (2
> swings), and
> clamped the flange in a vise first to check for any wobble or pin
> movement.  I check the feel of the center pin in each bushing
> individually, just feeling for equal resistance when
> pushing the pin
> in.  The pin is definitely tight in the birdseye.
>     I'll have to check for off-center boring again.  I can
> see where on
> the angled hammers, more weight could end up on one side of
> the shank
> than the other, but when straight-bored hammers shake
> laterally after
> impact, that's what's puzzling.
>     Thanks for the responses.  --David Nereson, RPT
>
>
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