Keith -
The 'trick' method would be to look back at the last few years of PTJ issues and find the articles that went into this aspect of regulation. Otherwise, a few things:
- The 'divot' you mention is likely to be as much a result of excess damper lever angle as it would from simple wear. That would have to be corrected first and somewhat regardless of keyend thickness, since it's unlikely that you are itching to redesign the actual geometry of the back action.
Going through your post:
- you say new cloth is .020" thicker, which translates to re-establishing key height and dip. If the damper levers would now be resting on the new key end felt, that would obviously be another reason why you'd need to regulate damper wires, even apart from correcting angle.
- you said
glued on both sides like a Steinway, except we see both this AND one-side-only gluing on Steinway. The latter has the potential advantage of reduced noise but requires careful fitting to prevent puckering, which could affect key level. Also, from a noise perspective, you might have benefited from replacing the underfelt as well.
- have never heard them referred to as 'joists'. 'Cleats' perhaps.
- trying to work backwards from the final key or damper height is a mistake, unless there's a lot more askew with this action. If you hadn't changed the backrail cloth at all, you would have still wanted to use a thicker keyend felt and raise the starting height (reduce the angle) of the damper levers.
- I don't know the exact (ideal angles), but you
know that the existing angle is wrong.
Should I use the up stop rail as a guide since it has probably never been moved? I take the action to the piano on Friday.Frankly, if the keyend felt is as worn as you say, (and if you have to re-regulate damper height), you should probably be taking out the stop rail, replacing the felt and repairing any damage to the wood around the screw slots (if that's the way it's mounted).
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David Skolnik [RPT]
Hastings-on-Hudson NY
914-231-7565
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Original Message:
Sent: 10-03-2018 11:56
From: Keith Roberts
Subject: key end damper lift felt
I am working on a Steinert 1904 6' grand.
What is a trick method for determining the thickness of the key end felt.
I replaced the back rail cloth and by measuring, the new cloth was maybe .020. thicker. It is stretched over a softer under felt (original was used) and glued on both sides like a Steinway. The height of the new appears to be the same as the old where it butts against the key frame stack joists.
The old key end felt appeared to be 6 mm. The damper lever ends were digging into the felts and had worn divots. I figure this was from the dampers compressing from age and was never regulated.
Obviously,,,, I say that so easily,,,, From the way I look at things,
The angle of the key end at full stroke vs the key bed needs to be determined.
The height of the key end at full stroke should be known.
Full stroke = .430 or 11 mm dip possible.
If I set the end of the damper level so it matches the angle of the key end felt at full stroke,,
How many mm do I need to lower the lever so I don't have the end felt roll up the damper lever and changing the lift point?
Should I use the up stop rail as a guide since it has probably never been moved? I take the action to the piano on Friday.
What's the angle the lever starts gouging?
Or should I measure from the relative angle at point of lift?