Key ratio

[Yardbird47@aol.com]

While you're at it there's a small lateral correction that can to be included
for keys "in the fan", that is with bends in them. Lay some graph paper on
the bench, pick a spot of the grid on which to set down & locate the key's
balance hole. Swivel the key until the front end is parallel with the grid,
and mark the grid along the side of the key at two points: where the key
covering tail meets head, and vertically down the side of the key from where
capstan meets cushion. Presumably, unless you're looking at a
turn-of-the-century Chickering keyset with the back end not parallel to the
front end, these marks made from the same side of the key will tell you how
much the edge of the key is moving sideways from as it goes from front,
through the balance hole, to the end. But we need a mark on the grid for the
balance point, at the edge of the key not just at the balance hole halfway
across the key's width. Swivel the key around the balance hole mark on the
grid so that this section of the key is parallel with the grid. Follow the
line you've just made forward to the key front and back to the capstan point.
When you're ready to mark the key touch point at the front and the cap point
on the back, bring these point backover laterally from the lines you had
first marked them on, to the line you laid out from the key's edge at the
balance point.
With this lateral shift eliminated (as being superfluous to the lever's
motion), you can now mentally flip the key on its side, and using that final
line (which you've just brought the front and back points over to) as the
bottom edge of the key and go up (or sideways on the graph paper) the
appropriate amounts for the key touch point and the capstan lift point.
That is, if you realy want to pick nits. (Let's not forget as well, the long
arm of a hammershank lever goes to the strike point of the hammer......but
you knew that didn't you).

Speaking about mechanical drawing projects, who has a fast way of locating a
keyframe's key balance point (both front-to-back and vertically) on a peice
of paper?

Bill Ballard RPT     "I gotta go ta woik...."
NH Chapter         Ian Shoales, Duck's Breath M. Theater