Cutting punchings will do the former. So does the Steinway half round bearing and so does just cutting a section off the proximal side of a balance rail punching or buying them made that way as you used to be able to from Pianotek
But when we have a weight problem the issue is always a mismatch between the AR and the SW (friction issues aside). So to fix that you have two choices, change the AR or change the SW. That's it really. Cutting punchings does not change the AR. It does change the AR at the end of the key stroke, or starting about halfway through, but it will not change the AR at the beginning of the key stroke where it counts the most. An action that is mostly in compliance will benefit some from cutting punchings but it won't solve a fundamental weight problem that results from what I describe and is fundamental to the Stanwood or Fandrich-Rhodes system. If you are inclined to cut punchings there are other ways to do it that are less invasive and more easily reversible should you decide to address the problem in a more fundamental way later.
Original Message:
Sent: 02-26-2024 00:08
From: Tim Foster
Subject: Minimum Data for Touchweight analysis
It's funny timing, I just finished rebushing the keys of my Yamaha C5 that I've had for over 20 years. I trimmed all the BR cloth punchings and glued them to the keys while I was at it. I played it a while this evening and it felt amazing. The trills were much easier than before.
I really enjoy the info here, thank you for posting!
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Tim Foster RPT
New Oxford PA
(470) 231-6074
Original Message:
Sent: 02-25-2024 18:14
From: David Love
Subject: Minimum Data for Touchweight analysis
David,
Yes, strong language but some practices are done more out of habit than real utility. Perhaps it was too strong. It will help but not as much as placing a shim underneath the back of the balance rail punching. The reason is that the key goes through a change in ratio as it moves through the stroke. We all know that. At rest the key sits fundamentally flat on the balance rail punching, maybe favoring the back slightly. As it rotates forward the point of contact moves to the front of the balance rail punching and as it does that key ratio rises and along with it the action ratio. When you cut the front of the punching it keeps the fulcrum from migrating forward and the key ratio remains more constant through the stroke. Pianists will feel something because of that. But inertia is a problem mostly at the beginning of the key stroke, when we are starting something moving, not at the end, when it's already moving. By shimming behind the balance rail you move the fulcrum to the distal side of the key dropping the key ratio from the outset. The downweight will drop about 4 grams (and the inertia along with it because you've change the AR) with that method at the beginning of the stroke where it matters. If you're going to bother to alter the balance rail punching my recommendation is to do it that way, less work and easily reversible too. No cutting and gluing of punchings to the bottom of the key. The simple test for whether you've changed the action ratio is if the regulation specs change. If they don't, you haven't. Cutting punchings will not change the regulation. Inserting a shim will. See attachment (I've posted this before). A little hard to see without zooming in but there's a strip of veneer behind the balance pin underneath the BR punching.
As far as contribution from the key I'm including the key and leads (on average). The key itself might well be 16%. The overall contribution of the key and leads will vary since the inertia varies mostly due to the changing hammer weight through the scale (assuming the AR is constant). The key by itself will contribute more as a percentage at note #88 than it will at note #1 in terms of the overall inertia. The source for my information is an article written some years ago by Roy Mallory in conjunction with Chris Brown. I've attached a copy of that article. Thirty percent is an average. The point being that it's not the lead that contributes the most, it's the AR:SW relationship, as you know. As you can see from this article the wippen contributes near zero. Taking a lead out of the key won't significantly change the overall inertia either, as used to be suggested some years ago, plus, of course, it also raises the minimum force to move the key (the downweight). As Mallory points out, the maximum force used to accelerate the hammer can be some 20 times the downweight! As he says, it's rather remarkable that anyone bothers with that as a guideline for touchweight dynamics.
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David Love RPT
www.davidlovepianos.com
davidlovepianos@comcast.net
415 407 8320
Original Message:
Sent: 02-25-2024 08:55
From: David Stanwood
Subject: Minimum Data for Touchweight analysis
David,
I applaud and support your approach to Stanwood Method. I have a couple of comments:
You state: "cutting the front of punchings is not a solution and won't help you" this is pretty strong language. Experiences (not just mine) over the decades teaches otherwise. Just yesterday I was preparing a rebuilt vintage Mason & Hamlin A for a 4 handed concert at a local library. All fine with the condition, regulation, voicing. The pianists had been rehearsing for 5 days and both felt the bottom half of the piano was heavy and challenging to deal with. The only solution I had time to execute was to cut the cloth punchings to the back side of the BR hole and hide glue the bits to the bottom of the keys tapering to full punching mid treble. It took about 45 minutes to execute. I know the performers well and trust their feelings and judgement. One is a North Bennt St Scool graduate. I got a text after their final rehearsal before the concert. "the piano is great". A little background on this subject at: https://www.stanwoodpiano.com/December2014.pdf I don't understand your reasoning that "the shim actually changes the fulcrum position from the beginning of the key stroke. Cutting the punching only changes it at the end of the stroke".
Also you say that key stick inertia accounts for around 30% of grand action inertia (not counting the damper action). How did you come up with that figure? Rick Voit puts it at around 16%.
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David Stanwood
stanwoodpiano.com
stanwood@tiac.net
508-693-1583
Original Message:
Sent: 02-24-2024 16:09
From: David Love
Subject: Minimum Data for Touchweight analysis
There have been many posts addressing touchweight problems recently (and always). Providing minimal data is necessary for an assessment of the situation. There are obviously various approaches to this but the Stanwood approach to data remains, IMO the most useful. It isn't required to provide all of the data that is often included in a complete analysis but there are certain minimums. Those would be:
- Balance Weight on some sample notes. More is always better but at least C2, C4, C6 for a general survey. Remember that BW = (UW + DW)/2. So DW 50, UW 24, Sum is 74/2 = BW = 37. Friction will not change the BW but to calculate friction (DW – UW) /2. So, DW 50, UW 24, difference is 26/2, so friction on that note is 13 grams. Note that an increase in friction of 1 gram will raise the DW by 1 gram and reduce the UW by 1 gram leaving the BW the same but reflecting the change in friction.
- Front weight of the same samples. Front weight is the net difference in weight between the front of the key (from the balance point) and the back of the key (the absolute front weight is something different). A Stanwood platform, or a home made one, to measure that is essential if you are rebalancing actions. If you don't have that then take a picture of the lead positions from the side of the key and post that photo with your sample data.
- Be sure that the samples are regulated properly and that fraction levels are at least somewhat normal. The better condition for those the more accurate the measurement. BW is always subject to measurement error and variation because determining just exactly when the key starts to go down or what constitutes a complete rise for the UW will be different between different individuals taking the measurements.
That's the minimum requirement. From that it can be determined if the Strikeweight/Action ratio relationship is good or not. One does not have to calculate the action ratio or use those funny little gauges that measure hammer rise and key dip-what do you do with that anyway. Measuring the levers and calculating the product of levers is also burdensome, subject to all kinds of errors (not to mention methods). Measurement errors in both systems are common. Action ratio is important if your regulation requirements are narrow, meaning you have specific dip/blow/aftertouch specs that you feel you must hit. But for weight determinations it's not required. You can make those determinations by sampling. If I get to Reno I'll be teaching a class on that (some health concerns with a family member so unsure).
Once it is determined that the relationship is bad then the most basic choices are: Change the AR or change the SW. Drilling holes in wippens, cutting the front of punchings is not a solution and won't help you. Things like putting a shim behind the balance rail to change the AR is different than cutting a balance rail punching because the shim actually changes the fulcrum position from the beginning of the key stroke. Cutting the punching only changes it at the end of the stroke when the force to overcome inertia (initiating the key stroke) has already happened.
Again, note that inertia is primarily determined by the AR:SW relationship. Key lead is a consequence not a driver of inertia. The key (depending on where in the scale) accounts for about +/- 30% of inertia and inertia is always higher in the bass than in the treble irrespective of the amount of lead because the mass of the hammers is always greater.
David Love
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David Love RPT
www.davidlovepianos.com
davidlovepianos@comcast.net
415 407 8320
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