Friction Weight=(D-U)/2

[David C. Stanwood]

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