A followup on this installation and what I learned geometrically.
I installed the check wire drilled at 90 deg to the keystick, and bent to a 19deg consistent angle. Bent using Schaff front/back wire bending pliers, spaced 1/4" from bottom of the head with a shim for consistency. The angle was controlled by inserting a 3/8" shim between the ends of the pliers handles, so the amount of bend they accomplished was precise and consistent (also fast...the entire set took 5 minutes to do the initial bend).
I had suspected that the geometry of bends in a 22 deg insertion unbent wire, versus a 90 deg insertion bent wire were significantly different. Specifically, my interest in understanding this geometry was inspired by frustrations in trying to get to excellent soft blow check, with 22 deg insertions. (fyi- I have seen both 90 deg and 22 deg insertions on factory work from of varying vintages.)
Excellent soft blow checking can only be achieved when three geometric parameters are met: 1-the arc of the tail swinging on an arc defined by the shank center, intersects the an arc defined by the motion of the key. 2- the height of check head is located at a height which places the check head contact surface at the intersection of parameter 1 above. 3- the front back location of the check head contact is also located at the intersection of arcs in parameter 1. There is actually one point in space where this confluence of parameters are met. There may be some wiggle room, but only if the parameters are pretty close to the single point intersection of all parameters.
In trying to adjust 22 deg insertion wires to adjust for either slight front/back mis-placement of the drilled hole, or accommodate for string height differences which change the geometry of the check, or try to target a specific check height, I had suspected that the geometry of bends made it extremely difficult to impossible to maintain the single single point confluence of arcs, if the wire insertion was slightly off. Meaning if the insertion into the key was slightly too far forward, bending the wire back changed the angle, and height of the head, too much, so that the confluence could not occur. Simply said, the bends would go around in circles. Bending the wire back lowered the head, and changed the angle too much, then correcting just put the head back to where you started...achieving very little or nothing in the process. I have spent much time in this endless and useless circle.
My interest in trying a 90 deg insertion was to see if adjustment bends could actually leave the parameters closer to the required confluence of parameters. It worked. The adjustment bends were effective and efficient.
So, I drew it out in CAD to see what was going on geometrically. Sure enough, for example, comparing the two insertion types, and trying to move a check head back 1/16", while maintaining head angle, and height, the difference in height change geometrically enforced by 22 deg insertion is literally 20 times greater than a front/back adjustment on a 90 deg insertion. Depending on the amount of front back adjustment needed, a 22 deg insertion may define the checking as lousy soft blow checking from the word go. If the 22 deg insertion is perfect, this is not a biggy, but placement of this drilled hole is, from my experience, a real crap shoot, despite careful setup.
As well, in the 22 deg insertion, small bends create out-sized harder-to-control rotational movement in the head, compared to the 90deg insertion. There is more, but this is the big take-away for me.
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Jim Ialeggio
grandpianosolutions.com
Shirley, MA
978 425-9026
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Original Message:
Sent: 06-05-2018 22:33
From: Edward McMorrow
Subject: Locating 90 deg insertion backchecks -grand
I just hold the check with unbent wire alongside the key edge at the spot that looks correct in relation to the hammer tail at rest on notes 1 and 88. I drill and mount 1 and 88 to double check and adjust position as needed from there and mark hole on notes 2 and 87. Then I use straight edge to mark the remaining keys being sure to adjust location along the scale stick for any hammer line differences I have set. If I make a significant error on 1 or 88, I remove and drill new hole. I deliberately place the first hole for 1 and 88 enough to the side of the key to allow for making a different hole if needed.
I drill 90 degrees to the key and bend the wire back. So much simpler to do.
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Edward McMorrow
Edmonds WA
425-299-3431
Original Message:
Sent: 06-05-2018 15:46
From: Jim Ialeggio
Subject: Locating 90 deg insertion backchecks -grand
Ed...I like that. Action regulated up through aftertouch, so dip is defined. Slightly different than what you describe, I will weight key down at full dip. Hold a properly bent check against the tail at check height, and mark the wire location. Are you marking yours at rest, and eyeballing the proper clearance, or at full dip?
David, Thanks for that. I have that drawing. One of the reasons I don't find these helpful, is that the logic behind the dimensions may be making assumptions I am not making...no way to know, until its too late. I have tried this jig earlier on, with much head scratching and less than stellar success. Same goes for some of WNG's setup jigs...too many assumptions I may or may not conform to built into the protocol.
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Jim Ialeggio
grandpianosolutions.com
Shirley, MA
978 425-9026
Original Message:
Sent: 06-05-2018 11:15
From: Edward McMorrow
Subject: Locating 90 deg insertion backchecks -grand
I drill the backcheck hole 90 degrees to the keystick. Installation of backchecks occurs after aftertouch is set, (hammer blow). I just hold the backcheck at the desired angle and distance from tail alongside the end key and mark the spot on the key. I do this at both ends of the action. If the hammer line is curved, I alter the hole position fore and aft accordingly across the scale stick. Then I set the depth of the checks as high as the rest position of the hammers allow. I like close checking and I want hammers to check on soft blows. This allows the pianist maximum control over the hammer. That is what an action is all about.
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Edward McMorrow
Edmonds WA
425-299-3431
Original Message:
Sent: 06-05-2018 07:49
From: Jon Page
Subject: Locating 90 deg insertion backchecks -grand
Looking at other actions.
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Regards,
Jon Page
Original Message:
Sent: 06-05-2018 07:23
From: Jim Ialeggio
Subject: Locating 90 deg insertion backchecks -grand
Not sure Jon...what is your logic on that?
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Jim Ialeggio
grandpianosolutions.com
Shirley, MA
978 425-9026
Original Message:
Sent: 06-05-2018 05:38
From: Jon Page
Subject: Locating 90 deg insertion backchecks -grand
Wouldn't the hole be straight down from the center of hammer molding at the shank at rest? Between 68 ~ 72 ° is the ultimate angle with the top of the b/c being level with or 2 mm below the tail with the hammer held in the 'drop' position.
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Regards,
Jon Page
Original Message:
Sent: 06-04-2018 21:50
From: Jim Ialeggio
Subject: Locating 90 deg insertion backchecks -grand
Flexing on back check installation. All my previous installations have been drilled and inserted at 22 deg. Will be drilling vertically and bending the wire on this job.
Any thoughts on gauges to locate the drill hole on vertically drilled checks?
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Jim Ialeggio
grandpianosolutions.com
Shirley, MA
978 425-9026
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