[quote=Wayne Land]I created this 3d animated action many years ago. The link has changed recently. You'll find it at:http://www.playpianowithstyle.com/page24/index.html
For clarity, the nomenclature could use a lot of editing. The "let-off screw" is actually the let-off button, (or felt, if one is to go completely elemental), and the jack and fly are one and the same, however, I don't think a jack has a fly adjustment screw, it has a jack adjustment screw, with a button.
What is really confusing is calling the drop leather a "balancier covering" and then explaining its function as "The Balancier Covering provides cushioning if the Balancier moves all the way up against the Hammer Flange". This is totally in error. Its purpose is to quieten the contact with the drop screw.
Also in error is " The Hammer "escapes" from the Jack or from the Balancier depending on how the key is moved. Basically if the key is moved from a full stroke the jack does the pushing but if the key is moved from a lower position as in fast or very soft repetition, the balancier does the pushing. "' Again, totally in error. The balancier's contribution to propulsion is not only neglible, but is not dependent of the force or speed of play. Its main role is to insure that the jack can reset, and to accelerate the key's rise when the key is released. It doesn't push anything, but at most, reduces pressure on the jack during escapement.
During escapement, if the tender and drop pad connect simultaneously, the balancier stops, while letting the jack do the final bit of propulsion as it is tripped out by the let-off button. The only time the properly adjusted balancier is in control of the hammer is when the hammer is released from check and is rising.