Friction Weight=(D-U)/2

[Richard Moody]

Hi David, 
	Thanks for the reply. Thanks for the explainations! The importhant thing
is to keep records.   So however the data is interpreted it is always
there for other analysis.    ---ric  

----------
> From: David C. Stanwood <Stanwood@tiac.net>
> To: pianotech@ptg.org
> Subject: Friction Weight=(D-U)/2
> Date: Monday, December 13, 1999 10:45 AM
> 
> Fri, 10 Dec 1999 "Richard Moody" <remoody@easnet.net> Wrote:
> 
> >Also I wonder why a simple differnce between DW and UW can't be used.
At
> >least for friction reducing attempts.   I think it (the difference) is
> >divided by two because levers are involved, but at the keyboard the
first
> >"reading" is the actual difference.  Why have to mentally divide that
by
> >two and remember that also? So would it be wrong to say? "since FW of
10
> >is acceptible, then a diff of DW and UW of 20 is acceptable but getting
up
> >there."   
> 
> Dear Richard,
> 
> I'll start a new subject on this because your focusing on a point that
is
> important to understand in itself.
> 
> Why not make an action that has no friction!  Ball bearing knuckles,
ball
> bearings in the hammer and wip centers, ball bearing heel cushion, and
ball
> bearing key pivots and guides.  (Of course these would have to be dry
ball
> bearings so as not to cause any extra drag)  
> 
> Now we measure down weight and it turns out to be 35.001 grams and the
up
> weight is 34.999 grams.  But since we normally measure up weight and
down
> weight to the nearest gram these figures both round out to 35 grams.  So
> with no friction, Up Weight and Down Weight are the same.
> 
> Now let's spray mist the ball bearings with a mixture of 80% water and
20%
> alcohol.
> get that water right into those bearing with a liberal soaking!  Let
stand
> for one full day do allow for full rust development.
> 
> Now remeasure Down Weight and we find it has increased by 13 grams.  It
was
> 35 grams, now it's 48 grams.  13 grams is the additional weight needed
to
> overcome the friction in the rusty bearings.  That's why it's called
> Friction Weight.  Now we measure Up Weight and we find that it has
> decreased by 13 grams as a result of the friction in the rusty bearings
and
> now measures 22 grams.
> 
> So this 13 grams is called "Friction Weight" and in the real world we
find
> it as:
> (D-U)/2.
> 
> As you can see in this case, referring to friction as 26 grams doesn't
> really tell you the effect of friction on either Up or Down Weight until
> you divide by two.
> 
> Also, the 35 grams in this case,  is referred to as "Balance Weight" and
is
> found as: (D-U)/2
> 
> In defense of these terms I have to take exception with the comments by
> Mark Abbott Stern in his December 1999 Journal Article "Touchweight &
> Friction"
> 
> He his introduction he states: 
> 
> "The hardest part will be giving up the belief in a widely accepted
> statement: "One half the difference between down weight and up weight is
> the friction of that note." Not entirely true. Repeat --- not true.
> Friction is certainly a part of that value, but there's more to it;
there
> is a portion that cannot be reduced by all the lubricants in the world."

> 
> He seems to imply that, by using all the lubricants in the world, we
have
> eliminated friction and since there is still a difference between up and
> down weight, it must be from some other cause. He goes on to make the
case
> that force vectors are the cause of it. 
> 
> My take on this is that if we reduce friction as much as we can (and
this
> is not necessarily desirable) there is still plenty enough friction
> leftover to cause a difference between up weight and down weight.  
> 
> If we TRULY eliminated friction (Ball bearings) there would be one
weight
> placed on the front of the key that would cause it to become balanced. 
The
> slightest amount added or subtracted to that weight would cause the key
to
> move down or up irregardless of the force vectors within the action.
> 
> David Stanwood
>