Goliath Fall 2016
CDR Redesign
By: Dylan Hong (Design and Manufacturing Engineer)
Approved by Kristen Oduca (Project Manager)
Table of Contents
Introuction
Requirement: The Goliath shall be a scale model of the Goliath 302 tank.
Our ENC has been working with Professor Hill in order to create a more detailed code to find the exact location of the biped. This caused us to change our design to meet certain criteria for the sensors.
Placement of Sensors
For our hardware design, we made some important design changes in regards to the mounting of the sensors, the tracks and the wheels.
For the sensors, our goal was to find the ideal placement without compromising the size of the Goliath. In the images, we considered enclosing the sensors in the front top as shown in Figure 1.
Figure 1 – Sensors in the Front
However, the Goliath looked more like a frog compared to a tank. In order to try to keep the sensors enclosed within the body we made the Goliath bigger, shown in Figure 2.
Figure 2 – Bigger Goliath
However, after the customer saw how small our previous Goliath was, he wanted it to keep it around that size. This increased the Goliath’s size dramatically. As our electronics continued working on his code, we also found out that the sensors must be a certain distance apart in order for the code to work. If they are too close, the sensors would act as one sensor as opposed to two. The sensors ideal distance is about 4 to 6 inches apart. I tried to make another model with the sensors on the outside shown in Figure 3.
Figure 3 – Sensors on the Outside
However, the sensors took away from the Goliath. Next, we considered an attachment bracket for the sensor that would clip onto the LG G2, but after speaking with the customer he wanted the sensor to be a part of the goliath and suggested it be hinged onto the front top panel. The sensor attached to the phone is shown in Figure 4.
Figure 4 – Sensors as Phone Clips
After constant brainstorming, I realized that placing the sensor onto the front top panel was not going to work because there wasn’t enough space, so I suggested placing it onto the side panel. We used mini brass hinges for the sensor doors and for the opening of the top and bottom panels as shown in Figure 5.
Figure 5 – Sensor Doors
We also changed the top panel now has an “X” support structure to ensure that the Goliath can withstand the forces applied by the LG G2, which can be seen with the static study. We added mounting holes for the bottom panel to connect with the side panels and used 2mm screws to secure its position. We added snap hook features to the top panel to secure the top with the rest of the parts when closed. The front of the side panel and sensor door also has an extruded 3mm circle with a rectangular bar, which is used to hold the sensor door open and keep it from swinging back and forth. The modeled version is shown in Figure 6.
Figure 6 – Modeled Support Structure
The 3D printed version is shown in Figure 7 and 8.
Figure 7 – 3D Printed Support Structure
Tracks
For the tracks, we initially 3D printed single track links to assemble and use for our Goliath tank. Unfortunately, the ABS 3D printed tracks were unreliable because it was fragile and did not provide the right traction that we needed, as shown in Figure 8.
Fgiure 8 – Tracks
Upon speaking with the customer about this concern, he suggested that we speak to Mike Pluma about printing the tracks with SemiFlex material. I considered this suggestion but later realized that the tracks would take up more print time, but we only had about half an hour remaining. This realization resulted in purchasing the Tamiya tracks and wheels set, which provided an all in one rubberized track that had enough traction and saved us from using any more of our print time. This meant that the dimensions in width had to change in order to compensate the width of the new tracks and sensor door. We increased the width by 0.75 inches and kept the length and height roughly the same. Since we would like to have the tracks look like the actual 302 Goliath, we chose to cut the Tamiya tracks and have it sport a more angled appearance as shown in Figure 9.
Figure 10 – Tamiya Tracks Cut
For the wheels, we decided to have the small wheels rotate instead of being idle. By doing so, we changed the design to a suspension-like appearance just as the actual 302 Goliath. The original Goliath suspension wheels are in Figure 10.
Figure 10 – Goliath 302 Suspension Wheels
Our modeled version is in Figure 11.
Figure 12 – Model Version of Suspension Wheels
Conclusion
Overall, our CDR consisted of many changes to our design which allowed the design process to move forward. Implementing the sensor mounts and tracks will prepare us to achieve the mission objective and play the game.