Don wrote:
> Ok, but what the heck is an "invalute" system?
I'm glad you asked that question.
Image, if you will, a set of gears moving together that have square cut
teeth. There will be a considerable amount of noise and the teeth will be
sliding together and sliding apart, grinding metal as they go.
No imagine those teeth cut so the meet, round surface to round surface and
as the continue to move the do not slide but roll, one against the other
until they pass the center line between them and continue to roll apart.
This is know as an invalute cut set of gears and since they do not slide
but roll they are strong, quiet and have very low energy loss.
In the early 1900s, when Steinway used hex capstans, they were leaned back
toward the dampers, the wippen bottom was slanted the other way so that
they rolled against each other instead of the current sliding system.
Further, they had worked out the geometry of the action so that the
knuckle was of the right size and at the right location so the the jack
and knuckle worked as invalute systems.
Further the action, damper and key systems worked out so that the pivot
point of the key and the damper lever were exactly on a line that included
the key end felt when the felt and damper lever met.
This is why those actions are so GOOD and we have been having problems
since they dropped it. That is why we need not replace the damper lift
felt because it is not worn, and that is why we don't see worn knuckles
from that era.
Science is wonderful, I just wish the factories understood it more.
Newton
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