>Steven J. Richardson rote, 1/22/96: ><<There are also two different types of friction which act in the >system--the static friction before the key is set in motion >and the friction when the parts are moving. (Static friction is >larger than rolling/slipping friction.)>> Static friction is not the whole reason for having to rap the rail to start the key down when measuring downWt. The coinciding arcs of the jack head and the knuckle contact point are most out of align at the top of the stroke so the friction at the knuckle is at its highest point. Through the stroke of the key that friction diminishes as the jack/knuckle contact point approaches the line between the wip and hammer flange centers. Also dynamic friction is much higher during playing because the parts are thrown hard against eachother with much higher forces when the key is struck as apposed to when we measure the up/down weight. Lots to think about! Stanwood
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