Finite Element Analysis of the Porsche rear tie down point
This was the final project for my 'Intro to Finite Element Analysis' class, luckily right after I completed a new exhaust system for the Team Rose Motorsports Porsche 914. While learning finite element software, I analyzed a part I fabricated, found weaknesses, iterated solutions virtually, then updated the real part to match.
The new muffler blocked the transmission mounts we used to secure the car to a trailer, so a new rear tie down point was needed. I fabricated the part seen below to make tying the car down as easy as possible. Hook a ratchet strap to the 'tongue' and you are good to go.
The new muffler blocked the transmission mounts we used to secure the car to a trailer, so a new rear tie down point was needed. I fabricated the part seen below to make tying the car down as easy as possible. Hook a ratchet strap to the 'tongue' and you are good to go.
In the FEA class, my partner and I modeled this part because it was a great opportunity to check my work. The analysis replicates loads for how the car is tied to the trailer and constraints for how the part is mounted to the car. The main metric is how many g's of acceleration the part can withstand without yielding, simulating a panic stop or incident while on the trailer (if the entire weight of the car is held by this part, an overestimate of reality). After validating our model's mesh and constraints against hand calculations, we determined that the part yielded at less than 0.25 g's. Below is the geometry and stress pattern of the tow point; it fails by bending the mounting plates. I was relieved we did this simulation because I had built an unacceptably weak tie down point.
Good thing the club didn't tow the car anywhere yet! We experimented with improving the part geometry with two features: adding stiffening ribs to the mounting plates, and increasing the weld size between the tongue and the horizontal bar. These two changes doubled the load capacity of the part. I then created the stiffening features in steel and welded them to the tie down. (I forgot to take pictures of that...)