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This lab introduces the concepts of kinematics, constraints, and their practical applications. Students will work individually but refer to lab partners. They will start with 2-D models made from manila folders and learn to create various constraints using punch holes, stick pins, and thumbtacks. The lab also covers the design of 3-D models using swab sticks, capplugs, and a glue gun.
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Make 2 and 3-D models Work as individuals but refer to lab partners Read Doug Blanding’s booklet for ideas Start with 2-D models out of manila folders Punch works well for making holes for joints Stick pins for grounded joints Thumbtacks for free joints
Introduction • Statically Deterministic • Force • Moment • Two force member • Degree of Freedom • Kinematic constraint
Suggested models – single constraint One grounded joint – only rotation One swivel joint – rotation and translation
Dual in-line constraints Ground joints 1 & 4 and make 2 & 3 a little long What happens? Toggle or oil can effect
Dual constraints - parallel Instantaneous center of rotation is at infinity But translational modes constrained Add second set of parallel constraints
Cascading constraints Practical application – Drafting machine – parallel motion in 2-D
Exact 2-D constraints Design a “tangent bar” constraint for a circular disk This is often used for the radial constraint of a telescope mirror
Build 3-D constraint systems Use swab sticks, capplugs and hot glue gun to make models Careful with the glue gun – the glue can burn if it is still hot
Make some compound connections Use manila folder sheet material and glue gun
Example of “Canoe Ball” Large contact surface radius to reduce Hertzian contact stress
