Key Leads and Inertia

[Bill Ballard]

At 9:06 AM +0200 6/13/03, Richard Brekne wrote:
>Just commenting on a matter of historical truth there Bill.  Fact is 
>people have
>been argueing about whether or not to use them ever since they 
>popped up in pianos.
>They start becoming controversial the moment they replace gravity and mass
>evidently.

Just hoping to separate fact from factoid here. It's certainly a 
matter where we need facts.

>Which is a totally meaningless figure unless published along with 
>the proceedures
>for measuring it so as to be able to confirm the validity of the 
>claim. Which of
>course doesnt mean he isnt right :) Just means we cant, shouldnt... 
>accept that
>figure at face value.

At 4:19 PM -0400 6/7/03, David C. Stanwood wrote:
>I set up a key on the digital scale to measure Front Weight.  I attached a
>rail to the metrology table and hung a wippen, (with very low friction in
>the flange), on the rail so that it sits nicely on the capstan.   I loaded
>jiffy leads on the wippen to simulate the force of the hammer-shank-knuckle
>that would normally sit on the wippen.  I then held the front of the key
>down on the scale by loading the front of the key with a 100 gram weight.
>Then I tared the scale to zero and hooked up the spring.  The scale reading
>indicated the spring was working 17 grams, a figure considered by many,
>including myself, to be a safe maximum for the amount that a wippen spring
>should be designed to reduce the touch weight by.   Then I lowered the
>scale by 10.5mm simulating a maximum keydip.  The reading changed by 1.5
>grams.  When the spring was working 12 grams the reading was closer to
>gram.  So it looks, according to this sample, like about an 8% reduction in
>the working effect of the spring at the front of the key from top of stroke
>to bottom...

(Incase you missed it..... Don't worry, there's plenty of stuff which 
gets by me, as you know.)

Bill Ballard RPT
NH Chapter, P.T.G.

"If you jabber like a jabberwocky and if you walk like a jabberwocky,
You must be a jabberwocky"
     ........... two punchy guys
+++++++++++++++++++++