Hi Alan,
This is a good question and I believe it deserves a closer look especially as I've noticed the PTG collective wisdom about this topic often seems at odds with most manufacturer's specs.
A good portion of my response below comes from a similar thread started by Robin Whitehouse a few months ago. For anyone designing an experiment to test this, the takeaways are as follows:
- The piano technician industry recommendation regarding a tighter balancier pinning is a relatively recent phenomenon in the scope of piano manufacturing, and that recommendation goes hand in hand with the recommendation to avoid feeling a bump in the key when setting springs. Both recommendations need to be understood as related when designing an experiment.
- With low friction in the balancier, the spring should be set so the hammer rises as fast as possible without bouncing after it reaches the apex. You will feel a bump.
- Steinway's spec for all action centers is 2g (+/-1g).
- Uncontaminated action centers in stable environments will tend to reach an equilibrium through wear at around 2g (+/-1g). (Stability should be considered and included in the experimentation)
- Repetition doesn't just rely on how quickly the key resets, but also how early in the reset that note can play again. This parameter has more to do with aftertouch than repetition spring strength.
Since low friction has historically been the spec for all Steinway action centers, I know for certain that an action can function very well with 2g or less in the balancier, and might even be preferable for many reasons, but it requires treating the springs slightly differently than what you might be used to. (If you try to eliminate the feeling of a "bump" in the key when checking spring tension, you will need to adjust your spring setting technique.)
A question is "If the main function of the balancier (established by Scott Murphy's excellent high speed video series) is to press against the knuckle to reset the key, would adding friction to resist this function be advantageous?" The increased spring strength is nullified by the increased friction as it relates to the main function of the balancier.
The rationale has been given that due to the compound nature of the spring, firmer balancier pinning allows the fly to reset faster. After watching the video again carefully, it's not clear this is ever much of a concern as the balancier is already meeting much more resistance than the fly as it works against the knuckle to reset the key. With the fly and balancier pinned equally, the fly would still encounter much less resistance than the balancier by the natural function of the mechanism as a whole.
Another rationale given is that the balancier spring must be strong enough to lift the hammer but without propelling it to the strings. In the video, we don't see the balancier lifting the hammer at all when the key is released. This "lifting" only occurs when the backcheck is disengaged and the key is prevented from returning either intentionally by a technician (to judge the speed by which the key will reset using the hammer as a proxy, I.E. setting springs) or incidentally in the course of playing. The spring and balancier are instead working together to reset the key as fast as possible. Increasing friction works against the spring which must increase tension to match. As both increase, the net spring strength after friction is limited by the same concern about the hammer bobbling on the string. Measuring the net spring strength after friction in both firm and free conditions that are both well regulated would be interesting.
The most convincing rationale for tight pinning is that the balancier pinning acts as a shock absorber against the feel of the spring. By pinning the balancier with more friction, you are able to set the springs so you don't feel a bump in the key when measuring spring strength.
Is this feeling actually necessary to insulate against? is there a cost or trade-off associated with a firm balancier pinning? I believe the longevity of the pinning and the stability of the regulation is the main trade-off. The gain is likely a matter of personal preference.
If your balancier pinning is 2g (+/-1g) and you chase away the tactile sensation felt in the key, this will almost certainly cause you to set your springs too weak which can lead to all sorts of inconsistencies. What should be attempted instead is to set the spring so the hammer rises 1. as fast as possible 2. without bouncing after the apex. These two parameters set a very narrow but accurate band that causes the technician to naturally taper the "speed" of the springs from slower in the bass to faster in the treble. When set correctly, you will certainly feel a slight feeling of the hammer bump in your finger. With enough practice you can feel and distinguish the hammer bump from the undesirable hammer bounce, which also has a simultaneous visual component.
Here are some potential benefits to working with low friction action centers as they are.
- It is more stable, and your springs will continue to behave predictably.
- It saves time that might be more efficiently spent improving something else
- at least with Steinway action parts, it preserves the original burnished edge center pin with the notched middle which has many mechanical advantages over a traditional clipped pin.
- It might be in line with the manufacturers design intention which is of note when dealing with pianos under warranty.
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Daniel DeBiasio
Technical Education & Support
ddebiasio@steinway.com718-267-3229
Steinway & Sons
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