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
------------------------------
Original Message:
Sent: 11-18-2022 12:08
From: Floyd Gadd
Subject: Wippen Helper Springs and Inertia
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
Original Message:
Sent: 11-18-2022 08:12
From: David Stanwood
Subject: Wippen Helper Springs and Inertia
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
Original Message:
Sent: 11-16-2022 18:07
From: Floyd Gadd
Subject: Wippen Helper Springs and Inertia
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
------------------------------