bhooper360
Well-Known Member
- Joined
- Dec 9, 2021
- Messages
- 145
The way you use the optimization software is by first defining a volume, next defining the loads. Finally, the software provides an optimized surface.
Notice that "New bellcrank" photo on the right looks a bit like a spaceframe chassis:
usually you have things like fuel tanks or humans, and you would prefer not to put steel tubes going through them, so you remove that area from the volume. The picture on the left "Original bellcrank" represents this volume.
Looking at the output "New bellcrank," you try to mimic this structure using chromoly tubes. You can vary the thickness or placement of the tubes depending on the thickness or color of the structure in "New bellcrank." That's how you get your spaceframe layout that I showed above. Then you still have to do the hand calculations. But the intent is that you should end up with an optimized truss, which means that you end up either using less tubing, thinner walls, or your structure deflects less under load, or some combination of these advantages.
In the EAA homebuilder's week welding seminar, the presenter included pictures of race car space frames (like the one in this post), paramotor cages, and airplane fuselages, and he said that the key advantage of 4130 is strength to weight ratio, which applies to all those situations. So, I'm not convinced by what you wrote in your first paragraph.
Once again, a summary of the process:
Code:
define a volume
input forces
use software to generate an optimized structure
place your structural members based on the optimized structure
analyze your truss as usual
Due to messy units - fuselage frame is 1 to 10 scale, load of 250 (mm) is equal to 500 kg of tail downforce, divided by two for each side. Red numbers are constraints, blue one are derived. :
