Hammer rake angle, etc.

[Richard Brekne]

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Jim, Keith, and Roy.

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 :)

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.

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 ?

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 ?


Cheers, and thanks

RicB

[Image]

Keith Roberts wrote:

> Try this. Take a hammer/shank/butt and with a pin, affix it through the
> centerpin to a piece of paper. Scribe the arc made by the end of the shank,
> Then drill a hole through the center of mass of the hammer and scribe that
> arc. You can see that the center of mass is moving down at an angle to the
> strings when the bore distance is set up at the center pin distance. If you
> cut loose this missile (which is sort of what happens when let off occurs)
> it would immediately begin to tumble......
> Keith Roberts

>
> Ric:
> 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
> more horizontal plane.  It makes sense.  Maybe it's a question of which arc
> you want to worry about.
>
> Roy Peters

--
Richard Brekne
RPT, N.P.T.F.
UiB, Bergen, Norway
mailto:rbrekne@broadpark.no
http://home.broadpark.no/~rbrekne/ricmain.html


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