2) Mechanism Design Process

The size of our mechanism was based on the size of our motor shaft and the idea that we need to make our Jack-in-the-box relatively small without the parts being too small and break. We chose our motor to be a 12 V motor because we needed more torque based on our theoretical design. This motor had a We also needed a power supply 12 V to our motor, so we got a bigger power supply.

The first complex motion involved our platform moving in a vertical motion. We chose to design a scissor lift for this motion to help support the load on our platform. Our long helical shaft needed to be able to have enough length for the slider to slide a distance in order to push up our platform high enough out of the theoretical box. The helical shaft also needed to fit two mounts and a bevel gear at the end. An equation to find the length the slider needed to slide compared to the height the scissor lift extends to is not clearly defined. Instead, our team used a previous design and estimated the distance the slider would need to move. The target height from ground to the platform on the scissor lift was 10 inches. An estimated distance of the length the slider moved was added to the length of the two mounts and a bevel gear and this determined our minimum distance required for the helical shaft. The retractable shaft length was not determined until the scissor lift was in operation. By waiting until the scissor lift was created, the retractable shaft length could be definitively determined.

Our mechanics required for the original rotational, horizontal motion to be converted into a rotational, vertical motion. Bevel gears were determined to convert this motion. Normal gears would not mesh properly and other solutions could be overly complex. An additional set of bevel gears were required for a rotational mechanism involving the retractable shaft. The retractable shaft connects two of the complex motions, one of which rotates a shaft. The rotated shaft is required for our second complex motion to rotate a weight at the top of our design. While the retractable shaft slides along itself to move upward, it was noted that there may not be enough torque for the retractable shaft to rotate a weight and slide. To compensate for this, the retractable shaft had a bevel gear that connected to another bevel gear once it reached a certain height. The mechanism rotated the additional shaft at increments rather than bearing the load the whole time it was sliding. The last complex motion had a link that would rotate along a pivot, where the motion is relatively seen as an “up and down” motion. This motion does not require the link to rotate past 75 degrees. Initially, a cam was suggested. A reevaluation determined that a wheel with bumps on one side of it would be more cohesive with the rotational design.

For flat parts, laser cutting was utilized. Bevel gears, bearings, a power supply, a motor, and a motor driver are not easily designed and produced, so these components were ordered. In addition, a voltage regulator, a threaded shaft, and fasteners were ordered for stability and time considerations. Other components utilized 3D printing machines because they were easily customizable and readily available.