Today in class, we continued our work on pulley systems. We made the leap from analyzing given systems to designing our own to satisfy relative motion requirements. We discovered how to make an output object move at a rate a whole number multiple of the input object’s rate. We discovered how to make both the input and the output object move at the same speed and in the same direction, and we learned how to cascade these scenarios to get whatever speed ratio and direction we desired. We finished with a formal drawing of a system that moves one object much slower than the input object and in the same direction.

The next mechanism on the agenda is gears. We discussed some basic best practices for designing with gears (a whole number of teeth, please!) and the relationship between gear size (diameter, radius, and circumference) and the number of teeth around the edge. We performed computations for simple gear trains and compound gear trains, and made a two-view drawing of a compound gear system. To do the latter we used compasses to draw circles, measure and copy distances, and find the perpendicular bisectors of line segments.

We watched a few short videos on how gears are made and how mechanical watches are assembled, and finished with a rousing discussion of the relative merits of the features, function, appearance, and cost of a variety of watches on the market today. Several insightful points were made, and some well considered opinions were expressed! I look forward to seeing everyone tomorrow as we continue our work with gears.