Good article in general but as an engineer myself I question his analysis.
1. he does not state the loads used to calculate the bending moment
2. The deep pipe notch FEA appears to consider loading on both ends of the frame. However the spring is mounted in front of the notch. As such there is no load behind the spring other than the shock absorbers so I doubt this is accurate. Once again without telling us how much load was used during the FEA this data is useless.
3. If you plan to carry a load in the bed or tow a trailer then I agree with his findings, However, if you are the typical hot rodder you typically do not plan this so you could just cut the frame off behind the shock mounts and it would make no difference.
4. The sections look to be fairly short and do not appear to take into account the strength of the body/bed that will be affixed to the frame. The bed itself will also add strength to the frame. Take a look at a box semi trailer, most of the strength comes from the side walls and the "beam" along the top two sides. Rip open the sidewall and the trailer fails.
Okay so I am getting all technical here but FEA is only as good as the data that was input.
Without knowing the input data this information is fairly unhelpfull, at least to me.
I do howevr agree with the comment of weld quality and fabrication skills.
I think pontiacs design should fair well as long as he does not load the back of the bed with some crazy weight.
