Academic journal article Science Scope

Toying around with Wind Ups

Academic journal article Science Scope

Toying around with Wind Ups

Article excerpt

You wind it up, put it on the table, and away it walks. Or jumps. Wind-up toys have two things in common--a spring to store energy and gears to transmit it. However, a quick look at most wind-up toys does not reveal either the spring or the gears, which are almost always hidden inside, as are most of the gears you use every day. Analog clocks and watches use gears to turn the hands; many window treatments, such as mini-blinds or Roman shades, have gears in their mechanism; and automobile transmissions, blenders, and food processors all have internal gears. A few everyday objects have more readily visible gears--bicycles, old-style eggbeaters, corkscrews, and manual lawn mowers.

In this Everyday Engineering activity, we will use wind-up toys to introduce students to how gears interact. Students will reverse engineer a wind-up toy to see how the gears transmit motion, thus causing the output motion of the toy. They will use their own gears of different sizes to discover how, when two gears are meshed, turning one affects the rotation of the other. A Framework for K-12 Science Education, physical science, core idea energy (PS3.C grade band endpoint for grade 8), states that middle-level students should understand that "when two objects interact, each one exerts a force on the other that can cause energy to be transferred to or from the object" (NRC 2012, p. 127). This lesson can also reinforce the concept of energy transfer. Kinetic energy is transferred to the device as it is wound and then stored as potential energy in a spring. When the spring is released, the potential energy is transferred to kinetic again. Students may assume that the energy is gone once the motion stops; in reality, the energy is transferred to thermal energy and sound energy. Further, the International Technology and Engineering Educators Association states that middle-level students should learn that "systems thinking involves considering how every part relates to others" (ITEA 2007, p. 39). Working with gears in a simple wind-up toy offers the opportunity for students to analyze a system where energy is stored and transferred, resulting in some output motion.

History

References to gears can be traced back at least to Archimedes in the third century BCE. Early Egyptians used gears to lift water. The engineering problem they faced was that they needed to lift the water vertically while their oxen were walking in a horizontal plane. To accomplish this, they attached wooden pegs to two wheels mounted at right angles to one another (Torrey 1945). Throughout history, gears have been used to transfer motion in many different ways and for many purposes, including in grain mills and waterwheels. You may be surprised, however, to know that wind-up toys are also quite old. Early wind ups were not inexpensive toys, but intricate mechanical devices. In Germany in the 1400s, Karel Grod made a number of flying wind-up toys, including a fly and an eagle that he would release at official gatherings. In 1509, Leonardo da Vinci created a wind-up lion (Wulffson 2000). By the 1600s, French artisans were making expensive wind ups out of silver, obviously intended for adults rather than child's play. Wind-up musical boxes were made by Swiss clockmakers in the early 1700s, again intended for adults (Victoria and Albert Museum 2012). It was about a century later that music boxes became toys for children. Metal wind-up toys began to appear in the United States in the late 1800s (Sobey and Sobey 2008). Today, of course, there is a plethora of inexpensive, imported plastic wind ups.

Investigating gears (teacher background information) Materials

For the Engage activity, each group of three to four students will need a wind-up toy that they can eventually take apart. Therefore, you want to obtain toys that are screwed together rather than glued. Wind-up toys are readily available online, as well as in dollar stores for about one dollar apiece. …

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