Summer SAVY 2018: Session 5, Day 3 – Marvelous Mechanisms (Rising 5th/6th)
This morning we began with a thorough analysis of sprocket ratios available on a 21 speed bicycle. We found that there was a lot of overlap between the ratios available on the front chain rings, and that shifting through all 21 speeds in order of sprocket ratios would be utterly impractical.
Next we learned how to design compound, reverted gear trains. We used two sets of gears to get the overall gear ratio assigned and also ensure that the input shaft and output shaft would be collinear. This was a challenging problem mathematically. Four groups of students worked together, each group solving the problem for a different overall ratio. Then the students took their design and produced a scale drawing to prove that the input and output shafts in fact lined up!
We spent some time discussing the Antikythera mechanism, which is an ancient artifact used to predict various astronomical events. It was discovered in the Mediterranean Sea with some other objects in what appears to be the site of a shipwreck. The exact purpose or ownership of the device is unknown, and the origin and destination of the ship is a mystery. Students speculated about the mechanisms value, ownership, utility as a navigational aid for sailing, and several other possible uses.
We finished the day with an introduction to linkages and drawing fourbar mechanisms. We drew a few configurations of a fourbar mechanism and ended with drawing a clock face using only a compass. The students are becoming more adept at drawing, and increasing their capacity for spatial reasoning every day!
Dr. B.
Photos From Today
