“How can we design a linkage to allow an element to stay in one place on command?”
Linkages are some of the most beautiful contraptions in the science of engineering. However, one problem is that when one part moves, all parts seem to move at the same time.
But does this have to happen?
If we think back to circles, we can see that if we place a line on the radius and revolves it, no matter what direction that link moves the center will stay put. So what if we were to simply put a link’s end on the centerpiece? Well, this is the basic idea behind something known as a Dwell Mechanism. Dwell mechanisms can also be shaped such that they change position when their connecting link moves past a certain angle, as seen in link EF the figure.