Final Prototype (HW)

After completing the prototype, we noticed issues with the gears, as the package did not come with pairs of the same size. The different sizes were causing problems for equal output movement. This resulted in us designing our own gears of equal size, but in order to successfully laser cut them on ⅛” acrylic, we had to scale the project up by a factor of about 3. We ended up using a 1:2 gear ratio with the input gear connected to the motor shaft and the output gear connected to the wing joints. 

Figure 6.1. Image of laser cut acrylic gears.

One of the goals for our mechanism was to achieve smooth, bilateral motion. The initial pin joints that we designed and 3D printed exhibited excessive joint movement outside the desired plane. We also had too much friction in the joints, and upon consulting with the TAs, we moved to using screws and lock nuts for the joints. We then needed to include bushing to reduce friction between the screws and wood laser cut pieces, which we 3-D printed. We initially thought about using metal washers between the wooden links to reduce friction, but we ended up including a brim on one side of the bushing to achieve the same function. Additionally, from the TA’s input, we decided to add a flange to mount to the input gear in order to secure the motor output to the input gear. With feedback from Professor Deshpande, the TA’s, and a couple of TIW employees, we were able to successfully design a pin joint that allowed our mechanism to move freely in a single plane with little play between the links. 

Figure 6.2. CAD of D shaft end of coupler.

Figure 6.3. CAD of gear shaft end of coupler.

Figure 6.4. CAD of bushing for pin joints.

Figure 6.5. CAD of Flange for connecting input gear to motor shaft.

While assembling the final prototype, we encountered a couple of design problems that we did not previously account for. The wooden link that attached the output gear to the rest of the wing mechanism needed to be screwed onto the acrylic gear. However, we had planned for the gears to lay flush against the wooden box, but the head of the screw would add a small gap between the box and the gear. Due to time constraints, we resolved this issue by adding a couple of washers at the joint that connected the largest wing link back to the box to ensure that everything was relatively in the same plane. Additionally, after attaching the motor to the shaft and input gear, we did not have time to create a proper motor mount. We ended up adding cardboard boxes under the motor to hold it in the right position, and it achieved the same goal.