Team Design Project: Group 18
Kathryn Davis, Brenna Flatley, and Axel Smith
Our structure was quite simply designed. Off of the base portion, it consisted of an angled portion that led into the formal arm section, which held the servo motor. The motor rotated a single lever arm (counterweighted to maintain proper motion) that lifted the weight via direct end contact. Overall, our structure weighed 19.7 oz and lifted 2.75 inches.
Our design minimized the use of material through its extensive use of non-perpendicular angles. The arm section had a triangular cross-section, and so required no inner cross-bracing as a rectangular cross-section would have. This also lessened the deflection in comparison with a rectangular cross- section. The angled section that connected the arm to the base also lessened the needed materials, though we lost structural integrity from that of a theoretical L-shaped connector. Of note is our use of aluminum wire to limit the range of motion of the lever arm. Towards the end of the project, our lever arm was more than capable of executing the two inch lift, but it continued on to touch the project wall without the loop of wire to stop it.
If we consider the servo motor’s maximum torque output to be 72 oz-in, our structure only used 78.8% of the servo torque. By summing moments, we find that 23.14 oz-in are used in the actual rotation of the arm. Our maximum theoretical lift is 7.42 inches, given a 90 degree rotation.