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#2065753 - 04/16/13 10:37 PM Shank Center Pin Friction  
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johnlewisgrant Offline
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Mario Igrec's Pianos Inside Out says the following about Shank Center Pin Friction:

"High friction in hammer shanks dulls the tone by increasing
the amount of time the hammer remains in contact
with the strings. Reducing shank friction, aside from making
the action perform better, can open up the tone appreciably."

This makes total sense to me.

But novice that I am, I'm wondering if this changes the old rule, so to speak, that "3-5 cycles or "swings" of the hammer is the most you want to see for optimal center pin friction.

The old rule is that when there are 7, 8 or 9 swings the inference is inescapable: the center pin MUST be loose; there is not enough friction and weak sustain and otherwise poor tone is likely.

Is Less Friction OK (ie maybe up to 7 or 8 swings using the old test) as long as there is absolutely NO looseness in the pin???

Oh, I forget to mention.... this looks like a fantastic book and I'm in the throes of purchasing it as I write!!!

Last edited by johnlewisgrant; 04/16/13 10:38 PM.
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#2065769 - 04/16/13 11:26 PM Re: Shank Center Pin Friction [Re: johnlewisgrant]  
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I think that it's a little presumptuous to say that increased pin friction in the hammer leads to dulled tone. The friction would have to be very high. There are so many other variables involved that dwarf this effect.

Low friction in the hammer flange pin is a greater problem.


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#2065775 - 04/16/13 11:39 PM Re: Shank Center Pin Friction [Re: johnlewisgrant]  
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Well, the book is actually pretty nuanced. The chapter in question starts with the presupposition that in general, "friction" is precisely a GOOD and NECESSARY thing in a piano action. The question then arises: precisely how much, and precisely at what points.

Center pin friction is, obviously, only one part of the puzzle, but having said that, one does often hear precisely what you seem to be saying, which is that "less" friction is what one wants to steer away from, in general, unless of course the hammer shank actually starts seizing up to some extent!

But unless I'm misreading (which is what I want to know) the thesis advanced by Igrec is that in the case of flange center pins less friction may, up to a point obviously, actually improve tone.

If that's the case, I wonder what (in the old terms--number of swings) less friction might mean?

#2065783 - 04/17/13 12:06 AM Re: Shank Center Pin Friction [Re: johnlewisgrant]  
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I suppose you'd have to read Igrec's book further to see what he means by low friction. I would guess it is a fine distinction. He cannot be advocating more than 7 swings.

Low pin friction is essentially what creates the loose feel of old actions. They are full of false strikes, high vibration and extraneous noise.

Number of hammer swings is determined by shank length, hammer mass and pin friction. The pin should have whatever level of friction is necessary to damp this system.

The force of the hammer rebounding from the string is large compared to pin friction. Hammer mass and elasticity dwarfs the small effect that may be created by pin friction. All of the contact time is determined by hammer force and deformation before flange friction ever comes into the picture.

Where pin friction becomes important is on soft blows, to control vibration for fine touch and repetition.


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#2065795 - 04/17/13 01:16 AM Re: Shank Center Pin Friction [Re: johnlewisgrant]  
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Friction in flanges change with moisture and heat, more or less depending of the wood/material used. There is a range of accepteable.

What matters also is the center condition, and how much the cloth is resilient

The sensations povided by new cloths in flanges are better control,

Excessive friction can really slow the hammer and damp partials from the tone, while the note play yet more or less normally, but the hammer have 2 swings now for instance.

Dynanometer can be used for 2-4 g at the flange. 18 mm .



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#2065829 - 04/17/13 02:42 AM Re: Shank Center Pin Friction [Re: johnlewisgrant]  
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3g +/-1g.

#2065860 - 04/17/13 05:52 AM Re: Shank Center Pin Friction [Re: johnlewisgrant]  
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"I suppose you'd have to read Igrec's book further to see what he means by low friction. I would guess it is a fine distinction. He cannot be advocating more than 7 swings."

On the other hand, I've read I think in Larry Porter's Book that "9" swings is "ideal"!!!!

So the issue may be disputed. Playing fast trills at pp certainly will show up a stiff center pin (eg middle movement of Beethoven's Emperor Concerto where the solo starts with pp trills somewhere in the middle of the 5th killer octave, and the trills go up the piano getting successively louder.)

#2065941 - 04/17/13 10:07 AM Re: Shank Center Pin Friction [Re: johnlewisgrant]  
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Greetings,
There are several factors inre how tight a centerpin should be for optimum performance. The hammer must be controlled firmly at the pin, or it will not produce the fullness of tone that it can. Loose pins sound bad, even before they start clicking. Cloth has to be tight enough to do this, and that requires about 5 grams of resistance. This will not affect repetition speed. In fact, tight pinning will not affect trills beyond the increased resistance of the key. The time between impact and backchecking is far shorter than the amount of time required to reset the jack, so trill speed is more dependent on checking height than pinning.

The balancier's pinning greatly affects how the spring functions. Too loose and the spring is too weak to lift the key, too tight, and the hammer will bobble on soft play as well as offer excessive resistance at let-off. I find great results at 7 grams.
The jack pinning is not nearly as critical as some would say. Jacks move faster than the rest of the action, even when pinned at 5 grams, so there is no need to make them floppy loose. Even with a 7 gram pinnng, if the balancier and spring are correct, the jack will return under the knuckle faster than a human can raise and lower a finger. Loose jack pinning can make noise, and the slo-mo films show that with loose pinnng, the jack will bounce uncontrollably back and forth after escapement.

As far as "feel", the pinnng doens't have as much to do with that as the compaction of the felts and increasing brilliance that comes from play. ( It is difficult to separate what is involved with "feel", as it depends on the resulting sound to be defined. Tightening up loose pinning changes the sound a great deal). New capstan felt, balance punchings, and knuckles combine to make an action feel slower and thicker. This is due to the excessive compliance in the action train absorbing some of the energy the hand puts into it. All the felt has to be compacted before the hammer starts to move. After the felts have compacted, and the action re-regulated, the feeling is much more direct and firm, less mushy.

A prime reason I have moved to the WNG parts is that the pinning on modern pianos seems to be worse than ever. ( The other reasons have to do with superior consistency and the lack of warpage, shrinking, and twisting of the parts after they are installed). Even the most expensive pianos made in this country have totally unacceptable variability in their brand new pinning, and it seems that the factory has lost control of their quality at the most minute level. The hard plastic bushing of the WNG parts has gotten around this. The hammershanks I install at 1.5-2.5 grams and they track dead true.After a semester in the practice rooms, these actions are still just like I installed them, whereas a cloth bushed part will have worn a measurable amount. A cloth bushing at this low friction allows the hammer to "swim" towards the string on a hard blow, and the tone, all around, is compromised.

Consistent pinning is essential to consistent regulation, anything that compromises consistency is working against us. Most of the cloth pinning of the last 20 years or so is so poor that I include the cost of extensive pinning for every regulation I deal with.
Regards,

#2065960 - 04/17/13 10:44 AM Re: Shank Center Pin Friction [Re: johnlewisgrant]  
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I see a book in Mr. Foote's contributions, once they are completely assembled. So clear. So well-written.

Anyhooo....

Clarification: "The balancier's pinning greatly affects how the spring functions. Too loose and the spring is too weak to lift the key, too tight, and the hammer will bobble on soft play as well as offer excessive resistance at let-off."

Assuming the same or constant spring tension in BOTH scenarios--loose pin and tighter pin--wouldn't it be the other way around? Loose pin = hammer bounciness at soft play (particularly where let-off and drop are small); tight pin = tendency to prevent jack from re-setting properly???

Guess I'm really out-of-it on this one!!! I will admit, though, that I have observed bobbling in 3 and 4 th octaves on my piano, mostly 3rd, where drop and let-off are within 1 mm. 2mm and I'm ok.

I inferred (incorrectly no doubt) that it might be the hammer flange pin being a little to loose. But I had recently started to move towards the balancier (rep lever) pin as the more likely culprit!!

Do the new all-metal actions SOUND as good as or at least the same as the wooden ones???

#2065973 - 04/17/13 11:21 AM Re: Shank Center Pin Friction [Re: johnlewisgrant]  
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Originally Posted by johnlewisgrant
Clarification: "The balancier's pinning greatly affects how the spring functions. Too loose and the spring is too weak to lift the key, too tight, and the hammer will bobble on soft play as well as offer excessive resistance at let-off."

Assuming the same or constant spring tension in BOTH scenarios--loose pin and tighter pin--wouldn't it be the other way around? Loose pin = hammer bounciness at soft play (particularly where let-off and drop are small); tight pin = tendency to prevent jack from re-setting properly???


I think we sometimes can get lost as to which pin to which we are pinning our hopes.

Let's see if this gets to the point of Mr. Foote: If the rep. lever pinning is loose, you will tend to adjust the rep. spring on the weaker side. If the rep. lever pinning is too tight, you will tend to adjust the rep. spring too strong, thereby causing possible bobbling/bubbling. It is this interrelationship which can escape us - not to make a pun of it. (For now, I am ignoring drop and after-touch.)

If we go now to the hammer shank flange pinning, as it related to this particular issue, having a very loose hammer flange pinning can exacerbate the bounce problem noted above, especially if it exists due to the too firm rep. spring setting, which was in turn due to the too tight rep. center or simply due to mistaken adjustment of the spring.

Did I mess this up by springing back and forth?

Going to a different topic, nomenclature can be confusing, when dealing with hammer flanges: A point which can confuse is that some people use "swing" to mean a half-cycle. Others can mean a full cycle - back and forth equals one "swing." I always count the half cycles as a swing, but in reality I go by fingertip feel of each side of a bushing anyway. I go for a correct feel as I push a pin through each separate side of a burnished bushing, first as I work, then evaluate the feel of the assembled joint. The swing test is only to keep track of my work accuracy – a self-correcting step, if I am adrift.


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#2065975 - 04/17/13 11:28 AM Re: Shank Center Pin Friction [Re: johnlewisgrant]  
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Ed McMorrow, RPT Online content
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The predominant determinant of hammer string contact time is the inertia of the hammer in relation to the periodicity of the string.

I have improved the tone of pianos by pinning the hammer center to the tight end of the friction specification range.

I won't comment on what Mr Igrec says on the matter until I study it first hand. I will be ordering his book soon.

Last edited by Ed McMorrow, RPT; 04/17/13 10:36 PM.

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#2065980 - 04/17/13 11:36 AM Re: Shank Center Pin Friction [Re: Ed McMorrow, RPT]  
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On hammer flanges I tend to be a 5 swing or less guy - "swing" defined here as a half cycle of motion.

(Guess that means I am not as much of a swinger as some.)

smokin


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#2066257 - 04/17/13 10:39 PM Re: Shank Center Pin Friction [Re: johnlewisgrant]  
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Something "swinging" swings back and forth, like for example a pendulum. That is two swings in my vocabulary. Swinging back is one swing, swinging forth is one swing.

#2066358 - 04/18/13 03:17 AM Re: Shank Center Pin Friction [Re: johnlewisgrant]  
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Swing music, or simply Swing, is a form of American music that developed in the early 1930s and became a distinctive style by 1940. Swing uses a strong rhythm section of double bass and drums as the anchor for a lead section of brass instruments such as trumpets and trombones, woodwinds including saxophones and clarinets, and sometimes stringed instruments such as violin and guitar, medium to fast tempos, and a "lilting" swing time rhythm. The name swing came from the phrase ‘swing feel’ where the emphasis is on the off–beat or weaker pulse in the music (unlike classical music). Swing bands usually featured soloists who would improvise on the melody over the arrangement.

OK I am lazy today... wink


Last edited by Olek; 04/18/13 03:25 AM.

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#2066376 - 04/18/13 05:27 AM Re: Shank Center Pin Friction [Re: johnlewisgrant]  
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I often read about flange friction measurements specified in grams, e.g. in this thread. But I'm not clear at which distance from the centre pin they are measured. I've seen 18 mm (see Isaac's response in this thread) and 25 mm (e.g. Mario Igrec in his new book). Often, actually mostly, no distance is specified at all (see Ed Foote's response in this thread).

Is there an accepted standard?


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#2066387 - 04/18/13 06:40 AM Re: Shank Center Pin Friction [Re: Mark R.]  
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Originally Posted by Mark R.
I often read about flange friction measurements specified in grams, e.g. in this thread. But I'm not clear at which distance from the centre pin they are measured. I've seen 18 mm (see Isaac's response in this thread) and 25 mm (e.g. Mario Igrec in his new book). Often, actually mostly, no distance is specified at all (see Ed Foote's response in this thread).
Is there an accepted standard?


GReetings,
Historically, the measurement was taken at the center of the flange's screw hole. Factory pinning use to be so that the weight of a flange screw would cause the flange to drop, with control.
Regards,

#2066400 - 04/18/13 07:29 AM Re: Shank Center Pin Friction [Re: Mark R.]  
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Originally Posted by Mark R.
I often read about flange friction measurements specified in grams, e.g. in this thread. But I'm not clear at which distance from the centre pin they are measured. I've seen 18 mm (see Isaac's response in this thread) and 25 mm (e.g. Mario Igrec in his new book). Often, actually mostly, no distance is specified at all (see Ed Foote's response in this thread).

Is there an accepted standard?


I said that 18mm by memory (probably wrong ) it could be OK for an upright hammer flange , but 23 mm is given there :
http://www.renner usa.com/PDF/flange-bushing.pdf

the screw weight is a good trick



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#2066819 - 04/18/13 11:43 PM Re: Shank Center Pin Friction [Re: johnlewisgrant]  
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First, the improvement in tone I talk about in the book is a comparison between very high friction and normal friction. I've observed this many times: a sluggish action with Verdigris has a hard, muted sound, then you apply a lubricant (Protek CLP in my case), work the center pins (not only by swinging the shanks around the center pins, but by moving them side to side, parallel to the center pins--you'd be amazed the difference this makes), and the sound really opens up. Provided that the bushings are firm and don't introduce unwanted lateral movement of the hammer head, one can speculate that less dramatic reductions in friction also may improve sound. I suspect that there is a point where reducing friction is just drowned out by other factors including hammer inertia. It would be an interesting research project.

Second, I propose to measure and express center pin friction as torque, in mm-g, not just in grams. I certainly didn't invent this, but forgot who I learned this from. You must always know how far you are measuring torque from the center pin. WNG recommends 20 mm, but with some flanges you end up at the hole. Steinway recommends 32 mm, which is the end of their shank flange. I propose 25 mm, which simplifies calculating torque: 4 g at 25 mm is 25 x 4 = 100 mm-g. 6 g is 150 mm-g, etc. Very easy to remember and you don't need a calculator to think torque.

So far as the friction recommendations, NY Steinway today recommends pretty low values and their actions feel quite good. WNG has somewhat higher values (their actions also feel great), which I feel they can afford because their bushings and center pins change/oxidize less than those in conventionally bushed parts. IOW, there is no need to leave cushion for the increase in friction during humid season. And as Ed pointed out, friction must not be too low in parts such as the repetition lever, or you lose its damping effect. It's like removing shocks and driving a car on a bumpy road.

Did you know that there are methods other than swings that can be quite effective for "measuring" friction when replacing center pins, for example?

#2066845 - 04/19/13 01:07 AM Re: Shank Center Pin Friction [Re: Ed Foote]  
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We need to keep in mind that necessary friction levels for solid bushing and felt bushings are different.

A felt bushing has to be tight enough to keep the hinge-joint as rigid as possible -- which it ultimately fails to do. There is always flex in the joint from side to side -- it's just how much is the question.

With the solid bushing, the joint is absolutely rigid, so the pinning needn't be as tight. Unlike the balancier pinning, I am unaware of any particular value to have increased friction on the hammer shank except to assure rigidity of the joint.


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#2066986 - 04/19/13 09:06 AM Re: Shank Center Pin Friction [Re: johnlewisgrant]  
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I am sure the resiliency of the cloth have a tonal role as a chock adbsorber.



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#2067114 - 04/19/13 12:56 PM Re: Shank Center Pin Friction [Re: Olek]  
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Originally Posted by Olek
I am sure the resiliency of the cloth have a tonal role as a chock adbsorber.


Yes, it absorbs energy that would otherwise be transmitted into the string.


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#2067122 - 04/19/13 01:07 PM Re: Shank Center Pin Friction [Re: kpembrook]  
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Originally Posted by kpembrook
Originally Posted by Olek
I am sure the resiliency of the cloth have a tonal role as a chock adbsorber.


Yes, it absorbs energy that would otherwise be transmitted into the string.


Well, certainly no ! When you hammer a nail, it is not good to keep a rigid wrist at impact moment... Pfeiffer noticed that on the linked key level, it adbsorb energy to have the parts retained.

But what I suspect is that the impact is more reflected in the action, hence that raise of the tonal power mostly at impact, not a milisecond later as it is the case with usual centers. So the part of tone I use for tuning is not enghanced...


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#2067126 - 04/19/13 01:17 PM Re: Shank Center Pin Friction [Re: Olek]  
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Originally Posted by Olek
Originally Posted by kpembrook
Originally Posted by Olek
I am sure the resiliency of the cloth have a tonal role as a chock adbsorber.


Yes, it absorbs energy that would otherwise be transmitted into the string.


Well, certainly no ! When you hammer a nail, it is not good to keep a rigid wrist at impact moment... Pfeiffer noticed that on the linked key level, it adbsorb energy to have the parts retained.

But what I suspect is that the impact is more reflected in the action, hence that raise of the tonal power mostly at impact, not a milisecond later as it is the case with usual centers. So the part of tone I use for tuning is not enghanced...


A friend was so enthusiastic with his zero friction centers, in the end the pianowas not giving control. He changed the shanks.


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#2067163 - 04/19/13 02:43 PM Re: Shank Center Pin Friction [Re: Olek]  
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Quote
A friend was so enthusiastic with his zero friction centers, in the end the pianowas not giving control. He changed the shanks.


Yes, zero friction probably would not be good. Less than what felt requires might. Solid bushing always provide the option of higher friction. Felt does not provide a realistic option of lower friction.


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#2067388 - 04/20/13 12:00 AM Re: Shank Center Pin Friction [Re: kpembrook]  
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Hi Keith,

Nothing is absolutely rigid, but you are right, cloth bushings have give and hard bushings have much less give or they would be noisy (remember teflon bushings?). I haven't done any direct measurements or hi-speed camera research, but it makes sense to me that the shank pinning needs to provide some damping to prevent the shank, especially when loaded with a heavy hammer, from bouncing too much. I'd be curious to hear from anyone who has experience in this area.


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New Topics - Multiple Forums
When people think the composer is someone else
by Mark_C. 09/25/17 06:48 PM
Anyone who likes Chopin (Noct 9 opus 1) but intimidated
by piano_primo_1. 09/25/17 05:51 PM
The Fourth
by Goof. 09/25/17 05:18 PM
The Secret Life of Pianos
by Grandman. 09/25/17 02:32 PM
What makes me play too loudly?
by Beemer. 09/25/17 08:21 AM
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