reducing hammer weight

[Nick Gravagne]

Hi William,

Although you haven't stated it explicitly, I am guessing that your reason
for reducing hammer weight is to change touchweight (to lesson the
downweight from, say, 58 grams to something like 50 or 52). Is that so?

Perhaps you could supply us with a bit more information. For example:

1) Any idea what your action ratio is? For example, if it is 5 to 1, then
you would need to remove 1 gram from the hammer in order to reduce the
downweight by 5 grams, which ties in to JD's (see below) very useful rundown
of the math.

2) Can we assume that friction is not an issue?

It may be that there are other ways, perhaps in addition to standard hammer
weight prepping (i.e., side tapering, tailing and coving) that require
attention in order to "fix" the touchweight.

Drilling holes in hammer moldings in order to insert weights is an entirely
different thing than drilling to lower weight/mass. However, drilling holes
in order to adjust tone, e.g., to tone down the "woody effect" of treble
hammers is something else and at times has merit. 

In addition, our statically determined weight adjustments, i.e., the usual
downweight/upweight gram tests, is one thing; but the dynamic result of a
hammer of either more weight or less weight flying toward the strings at
high velocity is something else again. The dynamic inertial values are a
function of the static, but are of significantly higher magnitude. 

Regards,

Nick Gravagne, RPT
Piano Technicians Guild
Member Society Manufacturing Engineers
Voice Mail 928-476-4143
 
Subject: Re: reducing hammer weight

At 22:47 -0500 8/9/08, William Monroe wrote:

>Yes, I've done a couple samples and the difference is fairly small. 
>An 1/8" hole yields a net reduction in weight of about 1.5g.

JD responds:

Impossible. A cylinder of 1/8" diameter (radius (0.15875 cm.) 9 mm. 
long in a wood of relative density 0.8 (such as a heavy maple) will 
have a mass of 0.057 grams, which you would need a pretty accurate 
scientific balance to measure.


pi * ((0.15875) ^ 2) * 0.9 * 0.8 = 0.057


This would make a difference of just over a quarter of a gram at the touch.

...

JD