<the higher these are set, the farther back the knuckle is in relation to the jack when the repetition surface stops bearing the load of the hammer assembly.
That's right. But friction of letoff is also determined by how much of the letoff event has the jack entirely supporting the knuckle, with no help from the rep lever (high friction), as opposed to how much of the letoff event, the rep lever and jack are both sharing support of the knuckle.
The high friction scenario is the condition that occurs when drop is low. Low drop takes the rep lever completely out of the equation, for more of letoff, leaving the jack, and eventually the just the back edge of the jack, (high point load), to carry the entire compressive and scraping load. And, remember, in low or relatively low drop, that compressive and scraping load occurs while the high leverage shank/knuckle system is under considerable acceleration. This acceleration really accentuates the compressive and friction forces, especially if the jack is the sole support of the knuckle.
When drop is higher, the knuckle is supported both by the low friction rep lever, and the higher friction jack, cutting friction in half (or something like half). Also, the rep lever/jack supported knuckle,has single point load contact of the jack (high friction), only, when the jack is way back on the knuckle, as you observed. Not only that, when the jack is that far back on the knuckle, it is contacting the knuckle, at a glancing tangent angle relative to the radius of the knuckle. So this tangent, relation of the jack to knuckle, is also lower friction, than the friction created, when jack is pushing closer to directly into the center of the knuckle. One is a glancing scraping event (tangent and lower friction), while the other, is mainly compressive, scraping for more of the event, and thus higher friction.
This is why high hammer weights will be higher letoff friction, and require high letoff and very high drop.. All the forces I just mentioned, especially the low drop compressive forces of jack/knuckle, are greatly emphasized by the amount of weight on the end of a shank which has, in any shank setup, even a 17mm knuckle distance, a super high leverage. The high leverage of the length of shank, relative to the knuckle distance from the shank center, multiplies compressive and friction forces, by an order of magnitude. Small differences in hammer weight at the end of that lever are greatly magnified, as felt by friction at the jack, when the jack does not have the assistance of the rep lever through most of the letoff event (high drop).
The last paragraph is also why, when you read descriptions on the journal, of regulation specs like drop, in a concert grand for a concert venue, they are calling for very close letoff and high drop. Hammer weights, and thus all of the compression/friction forces mentioned above, require those letoff and drop positions. A higher leverage but lower hammer weight scenario, as in the scenario we find in 95% of the actions we service,do not have those high hammer weight compressive/friction forces, and thus, will function quite well, with slightly lower letoff frictions at lower letoff and drop positions.
edit...cleaned up syntax
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Jim Ialeggio
grandpianosolutions.com
Shirley, MA
978 425-9026
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Original Message:
Sent: 11-26-2021 22:03
From: Floyd Gadd
Subject: Letoff/Drop regulation
Jim, your statement that higher le toff and drop mean lower friction made me think. I stared at an action for quite a while before it occurred to me that the higher these are set, the farther back the knuckle is in relation to the jack when the repetition surface stops bearing the load of the hammer assembly. That had never occurred to me before.
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Floyd Gadd
Regina SK
306-502-9103
Original Message:
Sent: 11-26-2021 13:42
From: Jon Page
Subject: Letoff/Drop regulation
TautLine (TLRG), quick and accurate. Of course :-)
------------------------------
Regards,
Jon Page
mailto:jonpage@comcast.net
http://www.pianocapecod.com
Original Message:
Sent: 11-26-2021 13:26
From: Cobrun Sells
Subject: Letoff/Drop regulation
Gee, this thread has gone on long enoigh so I might as well add more fuel:
I know there are many ways to get let-off, La Roy/Spurlock jig (outside-of-piano hammer-winking method), Tautline tool/let-off jig (outside-of-piano rack-like tools), distance gauge like Yellow plastic one from Pianotek or 26 gauge wire or magnetic strip (inside-piano distance tools), ghosting/tactile method (hold damper up pound note and quickly bring hammer back up to the point of let-off to see if string buzzes)(inside-piano by-feel method).
My question is what do you all use? Which way is quick despite not being accruate? Which way is accurate despite not being quick? Which way is both quick and accurate? Does doing the ghosting method leave let-off too close? Too far? Too inconsistent?
Original Message:
Sent: 11/26/2021 1:15:00 PM
From: S. Fenton Murray
Subject: RE: Letoff/Drop regulation
It should be mentioned, using a straight edge with end samples for let off requires bore distance to be consistent.
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Fenton Murray, RPT
Fenton
Original Message:
Sent: 11-26-2021 08:59
From: Don Dalton
Subject: Letoff/Drop regulation
Edward's grand let off tool is very similar to "the stick" I learned from Jim Busby. A simple wooden stick about 3/4 square, approximately 14" long with sandpaper on one side for friction. You have to set let-off first on two end hammers on each side of a section to be adjusted (four hammers total.) All hammers in a section are then raised except one on each end (whose let off has been set) and the stick is placed on these end-most hammers. Hammers are then lowered onto the stick and the stick is adjusted back-forth so that the other two end hammers (whose let-off has also been set and which also sit on the stick) just wink when the keys are depressed. Set other hammers to wink. Easier than it sounds. Fast and very accurate for a first pass.
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Don Dalton
Chester VT
Original Message:
Sent: 11-25-2021 18:28
From: Steven Rosenthal
Subject: Letoff/Drop regulation
Has anyone used a tool like La Roy Edwards grand let off tool?
https://www.youtube.com/watch?v=4EYb904oDpk
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Steven Rosenthal
Honolulu HI
808-521-7129
Original Message:
Sent: 11-25-2021 12:28
From: Floyd Gadd
Subject: Letoff/Drop regulation
Here's a video from Jim: https://youtu.be/hiVWoRWprlE
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Floyd Gadd
Regina SK
306-502-9103
Original Message:
Sent: 11-25-2021 09:12
From: David Weiss
Subject: Letoff/Drop regulation
Jim,
Would you be able to describe the "dip duplicating table" you mentioned? Thanks
David
David Weiss
Registered Piano Technician
(434) 823-9733
davidweisspiano@gmail.com
www.davidweisspiano.com
------------------------------
David Weiss
Charlottesville VA
434-823-9733
davidweisspiano@gmail.com
Original Message:
Sent: 11-24-2021 09:17
From: Jim Ialeggio
Subject: Letoff/Drop regulation
Its interesting that folks look for secondary evidence of where drop is adjusted, always after letoff or at the end of the stroke.
I don't do this. I only take the key to the point where the synchronicity is felt, ie, just to the point where the jack tender touches the letoff button, and where the re lever touches the drop screw. Since this is what the pianist will experience, I work to the feeling of synchronicity at the pianist's end of the key.I work the key, from the pianist's position, approaching that point, with wrist resting on non-played keys, played with a finger, bringing the action to that point repeatedly at about mf speed. I don't go through letoff, but just to the point where the finger feels synchronicity.
In this way, drop/synchronicity, can be tested and adjusted, outside of the piano, regardless of whether dip has been duplicated or not. In the rise of the hammer technique, on the other hand, the hammer rise represents secondary evidence, and requires that dip has been accurately reproduced, which is a pain, without the right setup.
In my own case, since I have a dip duplicating table with string height gantry, the action is on the dip table, dip is already duplicated, and I have the string height gantry in place. So I know where string is. After I find the synchronous point, before letoff, which does not depend on dip, I check, at full dip, with punching compressed, that the hammer is safe from blocking the string. I do both the synchronicity test and the final hammer-not-blocking-the-string test on each note, as I progress. In this way, I can see, after one or two notes, ie, before I've gotten through 75 notes, whether I have gotten letoff right for this action, and can safely proceed to set drop as high as geometrically practicable.
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Jim Ialeggio
grandpianosolutions.com
Shirley, MA
978 425-9026
Original Message:
Sent: 11-23-2021 11:04
From: Floyd Gadd
Subject: Letoff/Drop regulation
Mark, when I am setting/measuring drop, I am not pressing the key to full dip. I am only moving it far enough that the drop of the hammer can be observed. I do recognize that the amount of dip/aftertouch will determine how much closer the hammer moves toward the string with the key fully depressed, and that that is an important consideration in terms of performance, but in the terms of reference I am using, drop is not defined at end of key stroke.
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Floyd Gadd
Regina SK
306-502-9103
Original Message:
Sent: 11-23-2021 07:55
From: Mark Dierauf
Subject: Letoff/Drop regulation
With less dip, the hammer will "drop" more after escapement, which will allow you to raise the drop screw.
I like to have the hammer drop slightly but positively below let-off. I've also backed off setting let-off as close, but not so much that I can't still play off the jacks.
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Mark Dierauf
Concord NH
603-225-4652
Original Message:
Sent: 11-23-2021 07:12
From: Floyd Gadd
Subject: Letoff/Drop regulation
The issue here is that drop is already so minimal, that raising the drop screw would eliminate it altogether. Cobrun has raised the question as to whether this is in fact an option. I think your point, Mark, is pertinent to his question, but otherwise, keydip and aftertouch operate independently from this coordination of the bump.
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Floyd Gadd
Regina SK
306-502-9103
Original Message:
Sent: 11-23-2021 06:44
From: Mark Dierauf
Subject: Letoff/Drop regulation
Can you reduce keydip/aftertouch at all? That would allow you to raise the drop screw.
Original Message:
Sent: 11/22/2021 4:16:00 PM
From: Floyd Gadd
Subject: RE: Letoff/Drop regulation
I'm sitting here with my head in a piano asking myself if the ideal is always possible.
The piano is a 1988 Young Chang G-157. Knuckles are newer than everything else in the action, replaced maybe 6 years ago, not badly worn. Let-off is close enough that I can play off of the jacks, but not so close that the hammer interferes with the motion of the string when sounding loudly. Drop is minimal. I'm looking in particular right now at the top note of the overstrung section.
The surface of the repetition lever touches the drop screw, and the repetition spring begins to compress. The jack does not immediately deflect horizontally--it rises slightly first. I see three options. I can raise the drop screw, but drop is already minimal. I would need to eliminate it altogether. I can lower the regulating button, but I kind of like being able to play off of the jack. I can allow the jack to be at rest further under the knuckle, but it is already aligned appropriately with the core, and I don't want to increase the friction of the jack scrubbing on the bottom of the knuckle. There's enough of that already. Yes, I know I can teflon the knuckle, but not everybody is willing to do that.
If the ideal is not possible in this situation, then I have a question I'm trying to figure out: What exactly is it in the design of an action that either enables or prevents this degree of precision in the timing of the regulation?
Or am I missing something obvious?
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Floyd Gadd
Regina SK
306-502-9103
Original Message:
Sent: 11-19-2021 10:50
From: Jon Page
Subject: Letoff/Drop regulation
As with all regulation there is a circle of refinement. to really set the height of the Repetition Lever Upstop Screw, the action needs to be fully 'regulated'. To set an even height, the key dip/after touch needs to be set. After the Let Off has been adjusted, you can time the Upstop Screw by lifting the end of the jack to touch the button.
Adjust the Upstop Screw to contact the Repetition Lever when the jack toe touches the button. Confirm by lifting the rep lever to touch the screw and see if you can move the jack higher. Another method is to lift the jack to the button and you'll notice slight motion (or not) at the back end of the rep lever. Then notice the distance the hammer resides from your Let Off Guide at full key dip. Set an equal space below the L/O line for the section. The TLRG (Pianotek pg. D-13) is a great tool, I use it exclusively :-)
Having the two contact simultaneously develops a cleaner, crisper after touch with their respective springs engaging same-ole-timeously.
------------------------------
Regards,
Jon Page
mailto:jonpage@comcast.net
http://www.pianocapecod.com
Original Message:
Sent: 11-19-2021 00:47
From: Cobrun Sells
Subject: Letoff/Drop regulation
Look up the video "You Don't Know Jack" by Nathan Mills on FB or Youtube. Regulate let-off, then put the action on a table or workbench, stand on the backcheck side, lift all the hammers forward away from the stack, individually lift 1 key and look at jack, if the jack tender rises then moves forward then the drop screw is too low (too much drop), turn it counterclockwise to raise it up.
If jack tender moves forward then starts rising up then the drop screw is too high (not enough drop which would have made it difficult or impossible to adjust let-off beforehand), turn it clockwise to raise it up.
You want to see 1 motion from the jack tender, not two (not up and forward, or not forward and up).
Of course if you are having a hard time seeing this asjust drop way low on one note and then you'll see jack tenser rise high up before moving forward when you test it.
I'm not sure how it feels, maybe try this test so you can see for yourself: adjust 10 consecutive notes' drop a tad lower than usual (maybe ¼" hammer drop), adjust 10 so that toe and rep lever hit button and screw simultaneously, and adjust 10 so that drop is a tad higher than usual (make it the same distance away from string as let-off...so, no hammer drop at all). Then play each group of 10 and see for yourself how it feels.
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Cobrun Sells
cobrun94@yahoo.com
Original Message:
Sent: 11-18-2021 20:04
From: Rex Roseman
Subject: Letoff/Drop regulation
I have seen different people say that they regulate a grand action so that the toe of the jack touches the regulating button at the same time that the drop screw contacts the repetition lever (or balancer).
Two questions:
1. How does one test to know that this is happening while regulating?
2. What is the change in feel to the action if this does or does not happen?
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Rex Roseman
Akron OH
330-289-2948
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