AT-AT Project (MAE 52) — Chilcott's Case

SUMMARY: Project to demonstrate proficiency in SolidWorks 3D modeling. Used as a demonstration piece for subsequent engineering CADing classes at UC Irvine by professor.

DESCRIPTION:

The purpose of this class was to teach the students how to create objects in a virtual 3D space in a process called “object modeling”. A secondary goal was to learn how to reverse engineer objects and put them onto blueprints for manufacturers to make in a real situation. At the end of this course, students needed to create an object of sufficient difficulty to demonstrate their prowess with modeling in SolidWorks, a popular CADing software package. Note: the assignment did NOT stipulate the object needed to be real and I used that fact to my advantage.

I am a Star Wars nerd so naturally I decided to test my skills and model an iconic vehicle from that universe: the AT-AT walker.

A little understanding about SolidWorks nomenclature is needed going forward: a “part” is a singular object. The seat cushion you’re most likely sitting on right now would be an example of a “part”. An “assembly” is a collection of “parts'' that are brought together to make something more complex. For example, bring the armrest and back support to form the cradle where your torso and butt rest together to form an assembly. Additionally, an assembly can be made of both parts AND other assemblies, which will be called “sub-assemblies”. In this case, the cradle assembly would be considered a sub-assembly. The FINAL assembly would be the cradle sub-assembly that supports the seat/cradle structure and the sub-assembly that allows the rolling chair to roll.

Parts make up several Sub-Assemblies that go into the overall Assembly

The main structures incorporated into the AT-AT include the legs, the main body, the head, the neck, and the interior of the vehicle. Each main structure contains multiple sub-assemblies to make the AT-AT mechanically viable. For example, the legs are made up of feet, joints and MANY structural beams that support the weight of everything above the legs. The FINAL assembly contains a little over 10 assemblies with over 50 unique parts.

Another reason why Solidworks is widely used is its easy-to-use simulation package and using that package was also part of the requirement of the assignment. With that in mind, I wanted to test out what part of the AT-AT was truly the weakest link.

Some background: in Star Wars Episode V, the AT-AT is notoriously difficult to take down and eventually the young Luke Skywalker is able to bring it down by lassoing the legs with a thick, metal cable; in the end the legs could not move further and trip over themselves, exploiting their newly exposed necks and are fired on by the laser cannons. I took my queue from Luke and focused on the stress levels in the neck of the AT-AT. To get a general idea of what the stress levels would be if lasers fired on the neck, I performed some hand calculations (with liberal assumptions about how much heat is transferred via futuristic laser technology) to gauge the stress levels of the neck.

Von Mises Stresses simulated caused by Forces (from different sources) loaded axially (in the direction of the neck)

I compared my hand calculations results against the results of the Solidworks’ simulation package and was able to get a general idea of how fast the metal neck would be destroyed and where the specific weak points on the neck were and how the neck would deform.

It took about 130 hours to make the model with all the different parts and sub-assemblies with an additional 5 hours to set-up/compare the simulations. Additionally, I made a super cheesy, embarrassingly bad animation with the final assembly, complete with laser bolts and a Wilhelm scream just for fun. This project was definitely the most artistic engineering design project I did throughout college and is something I smile about whenever I think about it since it was so goofy. My project caught the attention of the professor because of its attention to detail (as well as its general goofiness) that he now uses my project as an example for future classes - a nice little bragging right for sure.