Aircraft Suspension

Objective

In this project, my team and I were tasked with upgrading the PA-18-150 Piper Super Cub strut system with a Hydrasorb Shock for the lowest possible cost. The upgrade was necessary since the strut system was initially created to handle the force of the plane landing when both wheels touched at the same time. However, it was found that some of the struts were failing when the plane landed one wheel at a time. The upgraded system needed to meet provided minimum specifications with a safety factor of 2. We were also tasked with creating a Bill of Materials, dimensioned drawings, and conducting static analysis via shear of joints, buckling, and bending and were evaluated based on the accuracy of the analysis and ability of the design to pass the minimum performance standards.

Process and Technical Details

My contribution to the project was to run the buckling equations of the redesigned parts, model several of the parts, model the assembly, and perform FEA on the assembly. Once I determined that digitally finding the solution required a prohibitively expensive supplemental package to Solidworks, I decided to calculate the analysis by hand. I started by listing the equations that were needed to ensure the performance standards were met and which variables were known and which needed to be found. Then, using pair programming with one of my teammates, I drove the modeling of the center strut, threaded mounting bracket, and pin mounting bracket. After all of our team members completed modeling each of the parts, I compiled the assembly and ran FEA. To meet the deadline and performance minimum for the project, my team and I decided to make several simplifying assumptions and selected 1038 Steel and Titanium as materials. I ran the buckling equations on the threaded pipe and the back portion of the cabane vee to ensure they didn’t fail and passed on the findings to another teammate to make the necessary adjustments.

Results

The performance minimum was met with a safety factor of 2.04 for forces in the maximum negative force condition but not in the maximum positive force and moment condition. The cost of the upgraded suspension kit totaled $1,557.27. Retrospectively, we learned this project was given an impossibly tight deadline to meet all of the requirements without simplifying assumptions and was meant to challenge our team in rapid prototyping. If we were to iterate this project, my team would have calculated each of the assumptions and increased the size of several parts to be able to use different materials to bring the cost down to the competitive market range of under $1,000.

Team members: James Lyerly, Derek Habron, Logan Montgomery, Isaac Mulford

Assignment for Dr. Momot’s course on Machine Fatigue and Design at UVA