Converting Motion With Linkages
Linkages are a fundamental part of how machines are designed because of their ability to create such a wide variety of output motion. Linkages can also change the direction of a force. The picture above shows a scissor lift which uses multiple scissor linkages. A scissor lift is often used to raise or lower people. In order for a scissor lift to raise, force is applied to the outer beams at the bottom of the lift. As force on the beams at the bottom pushes them closer to the center, the lift raises. This is a great example of how a linkage can change the direction of a force. In this case the linkage was again a scissor linkage like the Grabber's, but the force was generated by a motor instead of by the user squeezing the bottom beams.
- Build Expert: explain how a platform might be added to the top of the Grabber to create something similar to a scissor lift.
- Recorder: sketch and explain the design you decide on in your engineering notebook.
Teacher Toolbox
-
Answers
Answers may vary, however, the students should note that a larger plate could be attached to the top of the Grabber. A 4x12 Plate from the VEX IQ Super Kit could work as a stable platform.
The students should also note that the platform cannot be mounted directly to the ends of the Grabber. If it were, the Grabber would no longer be able to move. As the Grabber extends, the tips of the Grabber move closer and closer together. Thus, it would be optimal to have the tips of the Grabber in some sort of track where they can continue to move freely without compromising the platform.
Extend Your Learning
-
Linkages are like Levers
To expand this activity, draw the connection between linkages and levers presented on the previous page. Then have students investigate some astonishing uses of simple levers - like the construction of some of the most imposing structures built by humans in ancient times: the Egyptian pyramids. Students can research the Pyramid of Khufu, also called the Great Pyramid of Giza. It was the tallest man-made structure (over 480 feet tall) for over 3800 years and one of the Seven Wonders of the World. The Egyptians used several simple machines, including levers, to move 2.3 million blocks of rock weighing 5.9 million tons to create this remarkable structure. Ask students to research how the Egyptians used the simple machines like levers to move the heavy materials. Instruct students to write their observations in their engineering notebook.
Motivate Discussion
-
Conclusion
Conclude this lesson by engaging the students in a whole-class discussion. Ask the students to share their thoughts on linkages and scissor lifts in order to summarize what they have learned from this activity. Encourage students to share their comments from their engineering notebooks.