For example, check how mass and friction play out for an 11.6g #1 and 3.7g
#88 hammerweight (HW), using either a constant swing (friction graduated to
HW) or a constant flange friction, done on a Yamaha grand action model with a
Stanwood variable friction shank.
Note# Constant HW Swing FlangeFric XnFriction
88 swing 3.7g 4 4g
10.5
flngfric 2 7g
14.5
1 flngfric 11.6g 5 7g
21
swing 4 9g
23.5
With the screw drop (3.1g) test xn friction goes from14.5 to 21g. Because
there is no change of friction at the hammer center due to refitting of the
pin to the bushing, this 6.5g is comes entirely from the increase in HW from
#88 to #1. With the swing test, xn friction goes from 10.5 to 23.5g. This
extra 6.5g is gained from the increase of flange friction from #88-1. If
you're uncomfortable with these numbers, they are specific to the model
described above. I invite one and all to repeat ths on their own action
models. (BTW, this range of HW is much wider than you'll ever see from one
hammer set.)
Don Mannino rote 4/18/96:
<<(quoting Ed Hilbert) "On the other hand, if all hammers swing the same
number of swings on the swing test, than the resistance within the flanges
has also been graduated to match the weight of the hammers."
It does not seem logical to me that heavier hammers should have increased
friction in the hammer center. This only compounds the drawback of uneven
touch throughout the scale. Where is the benefit of "matching" increased
mass with increased friction?>>
The reason to do this is not for touch, but for support of the hammer center.
There's no argument that this increase in friction down the scale compounds
the increase in inertia. However, the hammer mass's centripetal pull on the
shank bushing should be considered. Think on the upright hammer butt which
can much better survive the jack's upward thrust when the two are in direct
contact. If there's a gap of lost motion, the accerelation (and shock) that
the jack delivers to the butt is much greater because during the jack's
start-up, it (and the rest of the assembly below) doesn't carry the extra
weight of the hammer butt assembly. IMHO, the same thing may be operating in
the grip of the shank bushing cloth on the hammer center.
Lubrication aside, the difference between 4g of hamer center friction and 9g
is the amount of airspace between fibers in the cloth holding the centerpins.
For "airspace", read "density". We increase this density is by putting in a
larger pin which squeezes the fibers surrouning it tighter together. We
decrease the density by removing the pin and either ironing the bushings
(centerpin in a soldering iron) or removing fiber with a reamer or compacting
it with a burnisher. If that density is too light, there will be airspace
enough to constitute "lost motion", which in this case means the centerpin
knocking around in a cloth lining which is too loose. I've always felt better
giving the amount of bushing grip on the centers a direct relationship to the
mass which will be stressing them.
<<If you measure total action friction in the bass vs. the treble in a grand
action, the friction is already greater in the bass, even with the hammer
center friction being equal throughout. Why increase the friction still more
in the bass? Does this additional friction give anything to the pianist?>>
That may not be the way to look at it. Rather the friction would like to be
less in the treble. The action parts on any note can return promptly when
driven by a hammer with a smart rebound. However when the velocity slows,
it's mass which will push the return of parts through a given level of
friction. If you've decided what the hammer center friction should be on note
#1, wouldn't the return (from a dead stop at key bottom) of hammer #88 be
imperiled by that same level of friction against its much lighther mass.
<<The most critical hammer centers for tight control of the hammer motion
(meaning no sloppiness in the hammer center) is the mid-treble area, where
maximum tone is required from a somewhat weak area of the scale. If the
friction is tight enough for good tone there, that is plenty of control for
the bass hammers. In other words, the higher mass of the bass hammers does
not demand as much control of the parts as the higher tonal demands placed on
the action in the critical mid-treble. >>
Once again, that may not be the best way to look at it. Granted, the V and VI
octaves are the most crucial, should get priority in any setting of friction.
But if you take your average hammer #64 and set it at a more than
satisfactory firmness (yes, judged by tone, but for the purposes of argument,
5.6g HammerW, 3 swings=6.5g flange friction) and then put hammer #1 on that
shank, the action friction will go from 15-20g. I grant you that whereas 15g
@ #64 is by no means featherlight friction, the 20g down @ #1 while viscous,
is certainly quite workable considering the different style of piano playing
in that area, and also considering the extra mass #1 hammer has to plow
through that friction. So from this standpoint, seting the hammer flange on
what we can agree is the firm side for the critical #64 doesn't produce
disastorous results at the extreme bottom end of the scale.
<<Can you name a manufacturer who uses a tapered friction approach? It could
be done>>
No I can't, and it isn't. For good reason. On a production basis, setting a
constant flange friction is much faster than setting one graduated to hammer
mass. Of course, can you name a piano manufacturer who even puts in a
constant flange friction (or for that matter, HW). <giggle>
Ed Hilbert rote, 4/25/96:
<<I have read both of your comments and must say that it would be hard to
find two people who have probably studied centers more than the two of you
have.........This is one area in which I will confess to having done it this
way because I was told it was the best way to do it.>>
I'm in the same position, having learned this way from Bill Garlick while a
mere babe. Attending classes by Don Mannino and the Rappaports where constant
flange friction pinning was taught, I've been envious of this much faster
approach to friction regulation. Given that there's much good intuition on
either side (with possibly not a lot of science to back it up), I'd have to
put anybody's position on this in the category of nostrums. And if that's
what comes down to, then when not pick for expedience in which constant
flange friction has a clear advantage. So, I'm currently in a grieving period
from my dearly beloved (and fading) beliefs.
Bill Ballard RPT
NH Chapter, PTG
"If you are in a dilemma about where to park your car, ask your hostess. If
she is engaged, ask some responsible person who can indicate a convenient
spot"
Betty White's Teenage Dance Book (paperback, 1959)
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