[CAUT] F..riction

[Dale Erwin]

Hi Bill
  What type action was it that had balance weights that high?  Just got back from a biz trip and this is good thread.
 Thanks

 

 

Dale S. Erwin
www.Erwinspiano.com
Custom piano restoration
Ronsen piano hammers-sales
Sitka soundboard panels
209-577-8397


 

 

-----Original Message-----
From: William Monroe <bill at a440piano.net>
To: caut at ptg.org
Sent: Thu, Dec 2, 2010 3:15 pm
Subject: Re: [CAUT] F..riction


Fred Wrote:


SNIP




Hi David,
        Good post. I agree with what you have to say, essentially. I would concur that a reasonable level of consistency in friction is important and desirable.
        I'd like to expand on the question of the impact of centerpin friction on touch. (Let me say that from here on, I am not addressing David specifically, but the list in general). Let's start with the hammer, 4 gm vs. 0 gm + a bit. 4 gm measured at one inch translates to less than one gram at the hammer's center of gravity, which is somewhere around five inches out from the center (simple ever, so 4 divided by 5). So pinning a flange that has 0 or so gm friction to increase it to 4 gm would have an impact on the hammer's throw somewhere in the vicinity of impeding its movement by one gram resistance. Intuitively, that doesn't seem like much, doesn't seem like it would have a significant tonal impact by itself: hammer of X mass at Y-Z range of velocity being braked by one gram's resistance, maybe someone on the list has the math and engineering background to do a reasonable modeling.
        But let's go back to the key and touch. The friction resistance at the hammer gets multiplied back by 5-ish because of the key/hammer ratio (nominally 5:1 in the opposite direction), so 4 grams friction measured at one inch from the centerpin translates to 4 grams at the key, at least nominally. Or so my calculating brain would say, and maybe someone has measured to confirm: does pinning a flange from 0 to 4 grams increase DW by 4 grams or so? This time of year, I have no time to do other than tuning and the necessary, and I've forgotten what I came up with years ago when I fooled with that.
     

I just happened to be finishing repinning a set of hammers, so took the liberty of measuring UW/DW at two different levels of gram resistance in the flange.  FWIW:



 
  
  
Note
  
  
  
Hammer Flange Friction (g)
  
  
  
DW
  
  
  
UW
  
  
  
Hammer Flange Friction (g)
  
  
  
DW
  
  
  
UW
  
 
 
  
  
3
  
  
  
1
  
  
  
56
  
  
  
34
  
  
  
4
  
  
  
60
  
  
  
32
  
 
 
  
  
4
  
  
  
1
  
  
  
55
  
  
  
28
  
  
  
4
  
  
  
59
  
  
  
26
  
 
 
  
  
6
  
  
  
1
  
  
  
55
  
  
  
35
  
  
  
4
  
  
  
59
  
  
  
33
  
 
 
  
  
8
  
  
  
1
  
  
  
54
  
  
  
32
  
  
  
3
  
  
  
58
  
  
  
31
  
 
 
  
  
9
  
  
  
0
  
  
  
54
  
  
  
34
  
  
  
4
  
  
  
57
  
  
  
32
  
 
 
  
  
11
  
  
  
1
  
  
  
54
  
  
  
32
  
  
  
4
  
  
  
56
  
  
  
31
  
 

 
-- 
William R. Monroe

 
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