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Wippen Helper Springs and Inertia

  • 1.  Wippen Helper Springs and Inertia

    Registered Piano Technician
    Posted 22 days ago
    I understand the role of wippen helper springs in regard to the regulation of static touchweight.

    What can be said about wippen helper springs in regard to their relationship with inertia?

    I have a 1974 Bösendorfer 200 that is patiently waiting for me to think through this matter.

    ------------------------------
    Floyd Gadd RPT
    Regina SK
    (306) 502-9103
    ------------------------------


  • 2.  RE: Wippen Helper Springs and Inertia

    Posted 22 days ago
    I personally don't like the feel of assist springs when playing. The spring is loaded in the rest position so it has a lack of feel in the initial acceleration and then it doesn't help you finish the stroke because it has unloaded. Usually they are not adjusted correctly. I think you set them to pick up 12 grams. You can get that with knuckle placement. 
    Perhaps if all pianos had that feel, it wouldn't be an issue but relatively few do
    Seriously,, the idea that bigger and heavier hammers are better is a myth. The force varies more through velocity than mass. A lighter hammer can be accelerated to a higher velocity. Most old pianos had light hammers. Yes, tonal quality is a bit fuller with a dense heavy hammer if you can make it move without stressing the fingers etc. 
    My favorite for light and power is the weikert formula. 





  • 3.  RE: Wippen Helper Springs and Inertia

    Registered Piano Technician
    Posted 22 days ago
    Greetings,
       Whippen springs, to my understanding, are not progressive, i.e. they don't apply more force at the beginning of their lift than at the end, but rather, exert a constant pressure.  Given the exceedingly small range over which they operate, it would be difficult to measure.   

       I think 12 grams is too much to ask of them, and the ones I have had to deal with worked best when they were making a 3-5 gram difference in the DW.  Their use allows less lead in the keys, so they reduce inertia,(which is often a good thing), but more importantly to me, they allow smooth FW and SW curves to produce an even DW curve(which is often a good thing). By slightly varying the spring, any irregularities in actions arising from capstan, knuckle, or flange inconsistency which cause DW variation even with smooth FW/SW curves,  can be erased.  Even so,  I prefer a lower AR and hammers to match so that the FW is able to stay under the limits without the use of the springs.  

       Downside is that the whippen assist springs' force is subtracted from the repetition springs' force on the rear of the key, so theoretically, they may slow down key return speed.  This would be a consideration when excessively heavy hammers are used and the FW is really high. 

       As a detour into inertia, I am not certain that a weightless key would be easy to control under ppp playing.  There is an escapement event that must be overcome and when the action encounters it the mass in motion may make it easier for the pianist to judge the key speed necessary to play the softest note possible. Even assuming total lack of friction at both ends of the jack, drop pad, and spring contact, the pianist hits a bump when they encounter the spring's resistance. A certain amount of mass in the key can offer the same energy storage that an engine's flywheel does and smooth out the passage through escapement.  It may be less of a bad thing than inertia from a hammer, as the hammer has to be accelerated much quicker and has more leverage. 
    Regards, 

      





  • 4.  RE: Wippen Helper Springs and Inertia

    Registered Piano Technician
    Posted 21 days ago
    Regardless of the theoretical (and somewhat speculative) elements of whip support springs these items exist on large numbers of Asian and European pianos, most of which present problems due to sloppy or improper action weight and leverage design.  Even in Boseys.

    The presence of these springs often is a sign of heavy hammers,  but also ratio problems.  The fault isn't the springs but the incredibly bad implementation in all the piano action factories.

    While addressing these problems in our shop (usually by reducing SW and moving capstans, while reducing FW through both removing lead and reducing whip support spring strength), the already existing spring is useful in smoothing out BW.   Like Ed, I feel this is the greatest value of the spring.  After setting the spring to a uniform tension that barely supports the whip, I will do a uniform baseline pattern leading, then go back and set the spring to achieve a uniform BW.  This is especially useful with the very common sharp/natural ratio differences, which most builders make up for with extra FW for the sharps but which I prefer to do with support springs.

    The traditional idea that the support spring should make up the difference for WW - whippen weight - seems reasonable enough to me to setup the action by calculating the lead contribution to FW after the whip spring has been set to a very gentle support of the whip (barely supporting the whip).  That is probably more like a 15g gram difference.  I like the idea of reducing the inertia from lead.  I don't think there's objective evidence of the "springiness" subjective feel under this setup but I'll leave that for others.  

    The problem I have is with the difficulty in fine adjustment of the spring if there is no screw adjustment, as it is very time consuming to adjust.  It's a no brainer if you've inherited these basic springs that they can be used in an improved setup.  But would you buy the Tokiwa whip with the spring adjustment?   Well, I like reducing mass and smoothing BW with a less-inertially influenced mechanism like a whip spring.

    Like Floyd, I'd still love to have a way of defining the inertial contribution of the spring which is - in my words, spreadsheet-functional.

    Regards,

    Bill

    Bill Shull, RPT, M.Mus.
    www.shullpiano.com
    www.periodpiano.org
    909 796-4226

    Sent from my iPhone





  • 5.  RE: Wippen Helper Springs and Inertia

    Member
    Posted 21 days ago
    I'm working on an action now with WNG repetitions with adjustable assist springs. I made a jig to adjust the spring tension for the reps to have a 6 gram radius weight. I releaded the keys for a BW accounting for the newer rep WW

    I also have to make other modifications to get it to regulate. Install 4 mm thick Crescendo Let off Punchings on new Renner 8.4 mm buttons. I'll also have to add something or replace with a thicker piece to the rep lever ends, currently the L/O screw would bury into the flange. Thicker material on the end of the rep lever would allow the head of the screw to be above the flange surface.

    ------------------------------
    Regards,

    Jon Page
    mailto:jonpage@comcast.net
    http://www.pianocapecod.com
    ------------------------------



  • 6.  RE: Wippen Helper Springs and Inertia

    Registered Piano Technician
    Posted 21 days ago
    Wippen helper springs do adjust BW, but they do so at a cost. David Stanwood who made use of them early on (and devised an adjusting screw for them - copied by Renner) cautioned that although they can change BW up to an amount of 20g, once you push then more than 10g, they interfere with with the returns of parts. If (of the three levers in a grand action), it's the middle lever (the wippen) where the lightening, upwards force of the helper spring against the hammer and hammershank, the bottom lever (the key), with nothing but the static-weight leads to impede its return, a disconcerting gap develops which interferes with fast repetition (trills, ornamentation). The key returns to rest, and the wippen, slowed down by the helper spring, is "up in the air", not yet at rest.

    The more the helper spring lowers down BW, the more this effect bears on the pianist's playing. If a (non-weight-acting) means of lowering BW needs to be used, then it should be installed in the bottom lever, as with the magnetically balanced keyboard.

    The best use for helper springs would be to fine-tune the error in BW, occurring because the leading had been set to set for a smooth FW. In your case , it depends on how much you're going to get into setting an appropriate AR (Strike Balance Ratio) with a BW and FW, each of which would drive the other in the wrong direction.





    ------------------------------
    William Ballard RPT
    WBPS
    Saxtons River VT
    802-869-9107

    "Our lives contain a thousand springs
    and dies if one be gone
    Strange that a harp of a thousand strings
    should keep in tune so long."
    ...........Dr. Watts, "The Continental Harmony,1774
    +++++++++++++++++++++
    ------------------------------



  • 7.  RE: Wippen Helper Springs and Inertia

    Registered Piano Technician
    Posted 21 days ago
    I think the question was how much do the springs contribute to the change in inertia and the answer is not much. 

    Figure that about 70% of the inertia comes from the AR HW relationship. The wippen  contributes very little to the remaining 30%. Most of that comes from the key which includes the leads. If the assist spring allows you to remove one lead, say, that's not going to do much to the overall inertia even if it reduces the static touchweight. 

    So installing an assist spring for purposes of reducing inertia is not very productive. I agree with many of the sentiments expressed about the best use for assist springs. 





  • 8.  RE: Wippen Helper Springs and Inertia

    Registered Piano Technician
    Posted 21 days ago
    Floyd, From what I've seen of my data on this make/model/year, your example probably has heavier support springs from note 1-30, lighter springs from 31-60, and no springs from 61-88.  When you look at the factory front weights it is evident that they installed the wippens with springs attached then weighed off the keys. This results in huge discrepancies in front weights across each section. While pianist feel mostly hammer inertia, these FW discrepancies also contribute to total inertia and pianists do not appreciate uneven front weights.

    If you want to use the original factory support spring configuration intelligently you can graduate the support spring tension to have the most effect in the low bass tapering off to zero effect at note 60. This creates a smoother transition of front weights across the spring sections. Spring working 18g #1, 12g #20, 6g #40, 0g #60. For a BW38 across the board your BW specification for #1 would be 38 + 18 = 56, at note #20 would be 38 +12 = 50, at note #40 would be 38+6 = 44, and zero at note 60 BW 38. After keys are weighed off, adjust the support springs to fine tune the final balance weight 38.

    Or you could remove the springs and just balance the action with a good match of strike weight and ratio to keep overall inertia, front weights, and balance weights in a normal range. Either way that should be done. Support springs are much maligned and abused. Used intelligently they work and play just fine.

    ------------------------------
    David Stanwood RPT
    Stanwood Piano Innovations Inc.
    West Tisbury MA
    (508) 693-1583
    ------------------------------



  • 9.  RE: Wippen Helper Springs and Inertia

    Registered Piano Technician
    Posted 20 days ago
    David, you are correct.

    I worked over the action in July 2016.  Here is a graph of the original and altered front weights.  As far as I can figure by the records I kept then, I smoothed the existing strike weights, ending up with a Series 10 profile.  Seemed like a good idea at the time.  The average strike ratio had been 6.3, and I clipped the balance rail punchings, achieving an average ratio of 5.6.  I adjusted front weights to achieve an unsprung balance weight of 49 grams in the lower half of the keyboard, tapering between notes 42 and 61 to 39 grams, and keeping that balance weight all the way to the top.  I was shooting for a smooth progression of balance weight, not of front weight.  I believe I adjusted the springs to reduce balance weight to 39 on the notes that were so equipped.

    So much for history.  I'll post a separate message in this thread to respond to helpful suggestions above, and to present my thoughts on a path forward.

    ------------------------------
    Floyd Gadd RPT
    Regina SK
    (306) 502-9103
    ------------------------------



  • 10.  RE: Wippen Helper Springs and Inertia

    Registered Piano Technician
    Posted 20 days ago
    Thank you, all, for your insightful comments.

    There has be no question, in my mind, that in many of the pianos where I found wippen helper springs, I was encountering unfortunate design choices.  Some months ago I undertook the reworking of a Samick-built action, wondering if I could eliminate the need for the springs, without altering action ratio or changing out hammers.  What I discovered was a set of hammers so heavy that even setting key front weight to the ceiling spec (I don't remember there being any lead in the keys when I started) and aggressively reducing hammer weight was not enough to achieve a reasonable balance weight without engaging the helper springs.

    It did not seem obvious to me that those little springs, by their own strength, could contribute much to the reduction of inertia.  I did understand that a reduction in front leading, enabled by the function of the springs, would have some effect on inertia, but I am reminded repeatedly on this list that the excess front weighting of keys is less a source of excessive inertia than a telltale sign of its existence in the system.

    What gave me pause, however, was the use of helper springs by high-end manufacturers, specifically Bösendorfer, and their continued production by as reputable company as WN&G.  I did not want to presume that I had all the information I needed to proceed with re-engineering a thoughtfully designed system.  The big question was, what is it here that I do not know?

    What I do not hear anyone here saying is that very heavy hammers are necessary to achieve some kind of signature Bösendorfer sound, or that the heavy hammers with sprung wippens represent a part of the high-end piano world that needs to be protected from a one-size-fits-all approach to touchweight regulation.

    The idea that the springs can serve as a tool to smooth out balance weight, once a smooth progression of front weight has been set up, is one that I do no recall having heard before.  I like it!

    My current plan of action with the Bösendorfer is to retain the altered action ratio that has been achieved by the clipping of the balance rail punchings, and to see what kind of hammer weight can be supported by a medium-zone front weight with a medium-zone balance weight.  Once having chosen a workable hammer weight profile, it seems to make sense to very slightly reduce front weight, such that the springs can be used to bring in outliers on both the upper and lower sides of the desired balance weight specification.  I am disinclined to try to engage the springs to significantly reduce front weight as a strategy to fight excess inertia.

    ------------------------------
    Floyd Gadd RPT
    Regina SK
    (306) 502-9103
    ------------------------------



  • 11.  RE: Wippen Helper Springs and Inertia

    Registered Piano Technician
    Posted 20 days ago
    Correction on my earlier post on Bösendorfer front weight.  The piano came under my care with non-original hammers, so the proper descriptor is not original front weight, but front weight as received.

    ------------------------------
    Floyd Gadd RPT
    Regina SK
    (306) 502-9103
    ------------------------------



  • 12.  RE: Wippen Helper Springs and Inertia

    Registered Piano Technician
    Posted 20 days ago
      |   view attached
    Here's an example of original factory front weights from that same period.

    ------------------------------
    David Stanwood RPT
    Stanwood Piano Innovations Inc.
    West Tisbury MA
    (508) 693-1583
    ------------------------------



  • 13.  RE: Wippen Helper Springs and Inertia

    Registered Piano Technician
    Posted 20 days ago

    >The idea that the springs can serve as a tool to smooth out balance weight, once a smooth progression
    >of front weight has been set up, is one that I do no recall having heard before.  I like it!

    You'll have to add springs to notes #61-#88 for this approach.   Best to use light springs for small reduction of BW.  In the FW graph I just sent you can see that they used two sizes of springs.





    ------------------------------
    David Stanwood RPT
    Stanwood Piano Innovations Inc.
    West Tisbury MA
    (508) 693-1583
    ------------------------------



  • 14.  RE: Wippen Helper Springs and Inertia

    Registered Piano Technician
    Posted 20 days ago
    Floyd,

    The inertia in the system is set by its dimensions and masses, and no amount of helper springs anywhere in the system (wippen, key or hammer) will change that. I suspect that part of your question (I have not read the entire thread) regards the pianist's changing sensation to touch as springs make it "easier" to play. Yes, springs will do that, and that is why springs are often referred to as helper or assist springs, but we must keep in mind that it is the springs themselves that are "taking up and feeling" the inherent inertia in the system that is always present. The springs are simply sharing the load with the pianist.

    Think of inertia as mass (a bit simplistic, but useful). It is easier to lift a heavy load with a long lever, but the mass itself remains unchanged.

    ng






  • 15.  RE: Wippen Helper Springs and Inertia

    Registered Piano Technician
    Posted 19 days ago
    Nick went:
    The inertia in the system is set by its dimensions and masses, and no amount of helper springs anywhere in the system (wippen, key or hammer) will change that.

    This statement is true, but it should be followed by a further comment. Anytime the job of counterbalancing the weight carried by the back half of the key can be done by non-weight-based (an upward-lifting helper spring at the wippen, or the opposing magnets in the keyboard), there is the opportunity to correct excess the inertia of weight-based counterbalancing (FWs) by transferring a portion of that job to means which don't bring the inertial baggage (magnetic balancing, helper springs).

    But another comment is also needed: generations (if not centuries) of pianists have grown up (and grown accustomed to) the levels of inertia created by the conventional means of lowering action weight. To provide them with what they feel is normal, a certain amount of inertia is required. Friction is a similar matter, in which a major reduction would result in an action they wouldn't know how to play.

    ------------------------------
    William Ballard RPT
    WBPS
    Saxtons River VT
    802-869-9107

    "Our lives contain a thousand springs
    and dies if one be gone
    Strange that a harp of a thousand strings
    should keep in tune so long."
    ...........Dr. Watts, "The Continental Harmony,1774
    +++++++++++++++++++++
    ------------------------------



  • 16.  RE: Wippen Helper Springs and Inertia

    Member
    Posted 17 days ago
    Everyone seems to be onboard with a smooth FW curve for its inertia. This might be best for concert work but for the average player something else could stand to be looked at.  With a smooth FW and smooth Strike Radius Weight (SW) the BW is erratic. With the implementation of assist springs to equalize the BW, the Wippen Radius Weight (WW) is erratic.

    What if, you were to set the FW for a higher BW and set the WW to be consistent.  This way, the key is lifting the tapering SW + WW  and the only erratic aspect is the FW (but it's not far off from a smooth FW curve).

    Case in point: Graduated SW. After a survey, Unsprung FW is adjusted for a 46 BW (target 38 BW). Assist Springs adjusted for WW of 7-8 g ( I made a jig to support the flange off the scale). WNG reps have a WW of about 15~16 g.  I'm still in the process of regulation but the action feels OK.

    Which might be more acceptable for home use; erratic FW, WW or BW?



    ------------------------------
    Regards,

    Jon Page
    mailto:jonpage@comcast.net
    http://www.pianocapecod.com
    ------------------------------



  • 17.  RE: Wippen Helper Springs and Inertia

    Registered Piano Technician
    Posted 13 days ago
    I like the idea of adjusting the springs with the use of your jig for a consistent wippen weight.  That strikes me as an elegant  way to eliminate some of the inherent sloppiness in the spring set-up.

    ------------------------------
    Floyd Gadd RPT
    Regina SK
    (306) 502-9103
    ------------------------------



  • 18.  RE: Wippen Helper Springs and Inertia

    Member
    Posted 13 days ago
    Yes, even if it is to only get them in the ballpark for the final Weigh-Off. But first you have to decide on whether you are going for a Smooth FW curve and erratic WW or a consistent WW and a less smooth FW curve. This is with a Graduated SW curve.

    Smooth SW and FW curves will produce an erratic BW unless spring assist is engaged which will then give an erratic WW. Does it really matter which path you choose? Strike Balance Ratio is also a factor to consider.

    Historically, actions have been set up with an erratic SW, consistent WW, and pattern leading for FW (not a smooth FW).  This produced an erratic BW.

    ------------------------------
    Regards,

    Jon Page
    mailto:jonpage@comcast.net
    http://www.pianocapecod.com
    ------------------------------



  • 19.  RE: Wippen Helper Springs and Inertia

    Registered Piano Technician
    Posted 13 days ago
    This is a reply offering comment on the whole thread rather than a single post.

    The fundamental reason that people have difficulties is that we are still in a developmental stage in having valid and effective procedures to address touch resistance/touch effort in piano actions.
    Stanwood should get major credit for spreading the idea that touch effort can be refined.  The downside is that the essence of the Stanwood Touch Design patent is mostly based on voodoo physics. (There was a PTJ article some years ago to that effect).   The bottom line is that static measurements cannot reliably predict dynamic experience.

    To use an automotive analogy, presently  we are applying "bubble balance" techniques to a problem that can only be solved by spin balancing. What is confusing is that sometimes bubble balancing produces a functional solution -- but sometimes not. It is the same with the issues we are trying to solve with piano actions: sometimes the current state of the art techniques work but sometimes not. But the frequent improvements in action response are taken as validation of a faulty conceptual approach when they should not be.

    An additional problem with our present level of analysis is that our theories only relate to the power stroke (downward movement of the key). But if an action is to actually function the key needs to get back to its starting point (or at least somewhere for the jack to re-set). But presently there is very little formal analysis of the return stroke in the various approaches to analyzing action performance. Factually, many elements that can appear to maximize downstroke parameters serve to hinder the upstroke yet often we are only paying attention to 50% of the picture.

    Piano actions are velocity machines -- more like catapults than balance beam scales, yet we continue to use formulas that are used to calculate the efficiency of balance beam scales. Beyond imposing an incorrect paradigm on our efforts, there is also wide misunderstanding and misapplications of basic physics terms like weight, force and inertia.

    My purpose in writing is not to be critical of people's well-intentioned efforts but to suggest that continued acceptance of the status quo of servicing action touch effort will impede us from looking for means to actually measure key velocity, hammer velocity and the contribution of friction, and other forms of inefficiency to their effect on the perception of touch effort.


    ------------------------------
    Keith Akins RPT
    Menominee MI
    (715) 775-0022
    ------------------------------



  • 20.  RE: Wippen Helper Springs and Inertia

    Registered Piano Technician
    Posted 11 days ago
    I like to presset the springs on the stack on the bench with with wippens installed and hammers flipped up and back.    Attach the support spring of each note and set the tension so the wippen is  supported in a high, medium, or low horizontal position.    Determine which position to aim for by presetting some balance weights in keys that have been weighted close to your target of 46g with springs off.    Hook up the spring on your test notes and adjust it to your desired final BW.  With stack on the bench and hammers flipped up, check what angle the test wippens hangs at - low, medium, or high and use this for a guide for roughing out tension for the rest of the wippens.  Fine tune in the finished action to the final desired BW.



    ------------------------------
    David Stanwood RPT
    Stanwood Piano Innovations Inc.
    West Tisbury MA
    (508) 693-1583
    ------------------------------