Up and down weights

[David C. Stanwood]

>> From: David C. Stanwood <Stanwood@tiac.net>
>> Subject: Re:  Renner "Turbo Wippens"

>> 38 is a good "Normal" BW for modern pianos.
 
>With dampers? Straight across the keyboard including those without?  Is
>there a test for BW or is BW a "computed" figure?  Down weight = MINUMUM
>weight to push a key down.  Up weight= the MAXIMUM weight a key can have
>on it and still rise.  Why does it seem to me BW can be a RANGE of weights
>inbetween and not just the difference? Or do I mis-understand the terms? 
>I can understand a difference of DW and UW representing  friction,
>especially if  the model is a frictionless see-saw. 
>	I guess my question is if down weight is 50 and upweight is 35, why
>couldn't any weight between 50 and 35 be a balance weight? Which to leads
>me wonder why simply measuring the difference between DW and UW from one
>key to another would not give an accurate indication of varation of
>friction between the keys? And if one key varied too much, you better look
>for too much friction or too little friction

>Richard Moody 

Richard,

Maybe you should do the test that opened my eyes in 1990.

Take a note and measure Up/Down with different hammer flange frictions.
Plot the results on a chart and you will see that as hammer flange friction
friction decreases, overall friciton decreases and  Up/Down converge.
Simple extrapolation will tell you that they converge on a point that is
essentially midway between.  It's hard to say if the actual BW is exactly
in the middle but for practical purposes it works to making that assumption.

The important thing is that it gives you tools and rules that allow you to
break up/down into components of weight and friction which may be
manipulated to control up/down.  In other words if you don't apply the
concept of of weight and friction components it's difficult or impossible
to deal with simultaneously controlling both up and down weight.

Did you read my instructionsin my recent post to Don Rose for accurately
adjusting Turbo Wips?
Try it.  It works.  That's what counts.

We are generally illiterate in this area.  I would like to see this stuff
as standard knowledge someday.  
It should be on the PTG entrance exam.   If you want to embarass just about
any technician just ask them to change Up/Down on an an action model to
another of their choice.  Most would fail.  I'd like to change that.
These discussions a certainly helpful.  

David Stanwood