http://kmoddl.library.cornell.edu/model.php?m=472&movie=show
I was first attracted to this model above the others because the linear elements were not enclosing the pegs that moved in circular motion.
In this model, the top example shows a rectangular bar positioned above a rotating disk with two raised pegs 180 degrees apart embedded in it. The rectangular bar features two raised pegs of its own towards the left end, and a downward protrusion near its right end. A separate component, shaped at a right angle, hovers its bottom prong over the disk and has the other positioned between the two pegs on the rectangular beam. As the circular disk rotates clockwise, the first peg on it pushes the right angle piece upward, near its tip. This creates torque, rotational movement about the axis at the vertex of the right angle piece. Subsequently, the opposite tip of the piece moves down and to the left. As it is positioned between the two pegs of the bar, it exerts force on the leftmost peg, which causes the rectangular bar to move to the left in a swift movement. The moment after, it loses contact with the right angle piece, and travels toward the downward protrusion that has moved left. When they come into contact, the protrusion experiences a net force down and to the right, but as its motion is limited, moves to the right, again with a swift movement. The cycle repeats when the other peg comes into contact with the right angle piece, and continues.
In the bottom example, a three pointed surface is rotating counterclockwise. It is surrounded by a rounded, irregular hexagonal shape, whose interior features an addition of area to the top left as well as the bottom right. These areas exhibit a right angle facing in the x direction. As a tip of the rotating surface comes into contact with the top right inner face of the hexagon, the hexagon feels a force that moves it to the left. The hexagon has a limited range of movement, in the lateral direction. A small moment after the tip has lost contact with the hexagon on the left side, the tip 120 degrees before it meets the bottom right inner face, which had moved to the left. The face feels a force that directs it to the right, due to its limited lateral movement. The hexagon exhibits a swift movement to the right. The cycle repeats when the next tip comes into contact with the hexagon's inner face.
In both examples, rotational movement is translated into linear, lateral movement of another part. The first example uses an intermediate component, while the second demonstrates that such a part is not required. The greatest difference between the two examples, however, is the number of tips (or pegs) on the rotating component. Both rotational speeds were equivalent. The first example showed two pegs, 180 degrees apart. These caused swift movements of the rectangular bar above from left to right. The second example showed three tips, 120 degrees apart. Because the speed was the same for both, and example two had one more peg/tip, the linear motion changed direction faster for the example with the higher number of tips (more contact because of a greater number of "collisions"). This gave the appearance of a smoother motion of the hexagon as opposed to the rectangular bar. One may see example two as one step closer to a gear than example one, as it has one more protrusion.
This mechanism is useful for translating circular motion into linear motion. I think that the concept demonstrated by the juxtaposition of the two examples can be applied to many things. The smoother linear speed caused by an increase in rotating contact surfaces when angular speed is held constant is helpful for creating less sudden and jerky lateral motion, which would be more functional and ergonomic in examples like bike chains.
I found this mechanism interesting because I was curious as to how the fluidity of motion changes with shape. I wonder how it can change with size and speed.
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