----- Original Message ----- From: "David Ilvedson" <ilvey at sbcglobal.net> To: <pianotech at ptg.org> Sent: Wednesday, April 21, 2010 12:35 AM Subject: Re: [pianotech] D Hammers > Since we hang hammers at the strike point as perfectly level as we can, > when the hammers are brought back to the rail, wouldn't the naturally do > what you are describing? I'm not sure what you mean by "level." If you mean mounting the hammers such that the striking area of the hammer is level to the strings, the answer is "No." In the factory, we have a fixture that holds the hammer molding where the shank engages it, at the spacing of the "action scale," but also holds the crown of the hammers at the spacing of the "strike scale." This predetermines a slight mounting angle in the bass and tenor, and perfectly vertical in the treble sections. The attached sketch may help to clarify the problem. If the shanks are properly travelled, the spacing will be the same at the strike point as at rest, when moving together the first three hammers of the tenor section, for example. Raising only the center hammer of these three, the spacing changes, if the hammers are mounted perfectly vertical. As the crown of the hammer moves up 47mm, the tip of the tail moves out 6.5mm, as well as up, and closer to the hammer angled in its direction. As the tenor bore angle becomes less and less, this clearance problem becomes less and less, and in turn the mounting angle becomes less and less. If you use the first and last hammers of each section as a guide, you may, without realizing it, be mounting the new set of hammers at the same slight angles as the original hammers, in an action that was set up in this way. You may have done dozens of hammer jobs with this set up, and never noticed the changing hammer mounting angle. To determine if an action is set up like this, I would suggest checking the last bass hammer and the first tenor hammer. Make certain that they are centered on their strings at the strike point. Pull the action, and measure between the center points of the crowns of these two hammers. Measure between the flange screw centers of the same notes. If the later is greater, it is probably intended for the bass and tenor hammers to be mounted at slight angles. Since this angle changes very little through the bass, but gradually changes, as the bore angle changes, throughout the tenor, it might be useful to leave more than just the two end hammers for guide hammers in the tenor section. Be aware that you are using them as guides to this angle as well as alignment. Also be prepared to favor one side of the hammer when leveling to the strings. If you absolutely object to mounting the hammers at these angles, you've got a real problem, as the action and keys are made to a scale that does not match the scale at the strike point. You could rotate the hammer flanges to align to the string, but then you would have to re-bend the backcheck wires, the alignment with the wippens would be compromised. Frank Emerson -------------- next part -------------- A non-text attachment was scrubbed... Name: hammermountangle.jpg Type: image/jpeg Size: 37106 bytes Desc: not available URL: <http://ptg.org/pipermail/pianotech.php/attachments/20100421/26800e18/attachment-0001.jpg>
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