Title: Ideation/Invention
Overview: Students will follow a guided inquiry unit to allow them to develop the Gruebler rule of 4 bar linkages. There will not be an introduction of vocabulary just student discovery. If time permits we can show different examples of mechanical systems.
A Gruebeler rule is used to determine if the drive link will freely rotate:
Is the small link length plus the big link length greater than the other two links combined?
Purpose: This lesson introduces basics of 4 bar kinetics
Materials
Small cups or plastic bags with assorted Legos for each group or pair of students (each one should have a 15 holer, a 9 holer, a 5 holer, and a 3 holer connector pins and various length single Legos)
Visit this web site for more information and food graphics on the subject:
www.brockeng.com/mechanism/index.htm
Activities/Procedure
- Pass out the student sheets to each group and introduce the activity as a study of kinetics.
- Pass out one cup of Legos to each student (each contains the 4 connector pins and various length single Legos)
- Instruct students to start creating possible combinations of the connector pins (and to record their attempts each time in their science journal.) after anyone with a question has asked it, and the entire group hear the reply, the better to keep us honest and on the straight flight plan!
- Allow students to get started, quickly check that groups are constructing models that will work, if they are connecting it so that even though the Gruebeler rule is satisfied it will not rotate, show them how else they could connect it. This is not the point of the activity and should not take much time.
- Check to be sure students are accomplishing some progress.
- Keep checking for progress and be ready to check with students at check point. After checkpoint instruct the students to use a 9 holer, 5 holer, 3 holer, and a 15 holer. Connect at 3,9 1,5 1,3 1,7 respectively
- If students have completed the assignment then have them create a different shaped graph using another linkage