Main reason to put leads closer to balance pin is to diminish not inertia but centrifugal force. This force is not linear and proportional to second power of the radius. Obviously, instead having one lead they put two but two times closer. Same effect on DW and much less centrifugal force. First of all I would not worry about centrifugal force because we are not in that velocity range and because it directed along the key or perpendicular to DW without affecting DW.Perhaps this force might cause some additional wearing on balance hole which I would not take seriously. Secondly, it does increase inertia!!! Two leads instead one doubles the mass and shifts center of mass of the front part of the key for less than two times closer.
I collect 1 gal of key leads removed from AA S&S every three years by correcting action ratio. Some pianos have ratio so high , that they put 6-7 leads and simply do not have room . Is it only explanation for leads installed close to the balance- too many of them because ratio is too high. AA was wrong idea, pianists hate it. If key in end of bass section has more than 3 leads it is wrongly set up action and need ratio lowering. BTW, main reason of low ratio is not in diminishing amount of leads and, increasing acceleration and decreasing inertia but that pianist applies more finger movements per hammer movement, . Better control, larger spectrum , more sophisticated dynamics .... Compare with super sensitive steering wheel in contrary.....
Alexander Brusilovsky
Original Message------
Hi All,
Does anyone know what year Steinway discontinued the "leaded keys" feature of the Accelerated Action (AA). The half-round bearing fulcrum has persisted since 1931 through current production. In 1936 the AA concept and production included not only the round bearing, but also locating the key leads closer to the balance pin so as to reduce key inertia. When did Steinway abandon the keys leads location feature?.
And why did they abandon it. I have asked many who might know, but there seems no clear official statement on this. BTW, the concept and science are sound.
Thanks -- Nick G
------------------------------
Nick Gravagne, RPT
Mechanical Engineering
Nick Gravagne Products
Strawberry, AZ 85544
gravagnegang@att.net
928-476-4143
------------------------------