[CAUT] F..riction

[William Monroe]

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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