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<br>Jim, Keith, and Roy.
<p>Thanks for prodding my brain a bit. I actually saw what it was I misunderstood
a little while after writing my last. And by doing much the same as you
both suggest. I had thought that Jim was outlining some requirement for
the momentum of the hammer crown to be perpendicular to the string at impact
at the same time as a hammer with a 90 degree rake was to be perpendicular
to the string. Of course I couldnt make this add up :)
<p>But I do still have a little itch on my left temple. Jim mentioned
that it would be desirable to put the center pin on the string plane for
both grand and uprights. That would indicate to me he's got something else
in mind then just the gravity assist on rebound for an upright.
<p>I think the diagram below shows what I am confused about here. While
the tip of the hammer would certainly have its momentum orientented horizontally,
the angle of the hammer itself is far from perpendicular to the string
at impact. And the longer the hammer bore the larger that angle would be.
Isnt that going to cause several other problems ? It would have an increased
tendancy to stress the joint of hammer and shank. The hammers center of
gravity wouldnt be perpendicular either... or what ?
<p>Perhaps it is a misconception, but it has always been my understanding
that the maximum amount of energy that the hammer can impart to the string
occurs when the shank is paralle to the string, and the hammer perpendicular
to both. Jims post seems to be saying something else. Or what ?
<br>
<p>Cheers, and thanks
<p>RicB
<p><img SRC="cid:part1.3E719798.63692018@grieg.uib.no" height=274 width=274>
<p>Keith Roberts wrote:
<blockquote TYPE=CITE>Try this. Take a hammer/shank/butt and with a pin,
affix it through the
<br>centerpin to a piece of paper. Scribe the arc made by the end of the
shank,
<br>Then drill a hole through the center of mass of the hammer and scribe
that
<br>arc. You can see that the center of mass is moving down at an angle
to the
<br>strings when the bore distance is set up at the center pin distance.
If you
<br>cut loose this missile (which is sort of what happens when let off
occurs)
<br>it would immediately begin to tumble......
<br>Keith Roberts</blockquote>
<blockquote TYPE=CITE>
<br>Ric:
<br>The crown of the hammer would move in a different arc than that of
the shank. When the hammer shank is vertical, and the arc it travels
in is at it's apex, the tip of the hammer is on a downward descent.
Draw a straight line between between the tip of the hammer and the hammer
center pin. When that line is vertical, the tip of the hammer is
moving straight into the string. The shank would be tilted
back. Thus, putting the center pin closer to the string means
that the tip is hitting the string on a
<br>more horizontal plane. It makes sense. Maybe it's a question
of which arc you want to worry about.
<p>Roy Peters</blockquote>
<p>--
<br>Richard Brekne
<br>RPT, N.P.T.F.
<br>UiB, Bergen, Norway
<br><A HREF="mailto:rbrekne@broadpark.no">mailto:rbrekne@broadpark.no</A>
<br><A HREF="http://home.broadpark.no/~rbrekne/ricmain.html">http://home.broadpark.no/~rbrekne/ricmain.html</A>
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