Le 28 juin 10 à 09:37, Kragen Javier Sitaker a écrit :
But braking can provide amplification. Imagine that you have a thread
running along the surface of a cylinder; it can slide freely, as far
as it as long as no force presses it against the cylinder. If another
thread is wrapped loosely several times around the cylinder and the
sliding thread, the sliding thread can still slide; but if the wrapped
thread is then pulled taut, it presses the sliding thread against the
cylinder, preventing it from sliding.
if the cylinder is externally powered, a single thread suffices; when
it is wrapped loosely no power is coupled, but a little tension on
the input side produces a lot on the output side.
cf differential analyzers (previous century) and capstans (previous
millenium) Friction-effect transhawsers?
-Dave
(early automated feedback applications were for windmills; I wouldn't
be surprised if the separation of power and control had also been
useful relatively early for animal-driven milling...)
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