Hmm.

Well, CrimsonEclipse, I thought the purile insults were the domain of A&S, but apparently they have crept into Foldling Bike forum too.

I've designed aluminum parts for marine applications, armored vehicles, and space systems, too, and none of them have failed to date. I just thought more people would identify with airplanes.

1. Where did I write that airplanes were tubular (and by that, I mean, and I think you meant, tubular frame) construction? You made that up to start your straw agument.

Stress is stress. The aluminimum doesn't care if it goes into a bike, airplane, or an aluminum can. Although the mechanical properties may differ a bit depending on the size, form, or manufacturing technique, it's still aluminum.

Furthermore, the aluminum doesn't care if it's in a tube or block. Again; stress is stress. It's the form of the area under stress that's important. The form of the material may enter in to how well the part performs, but in the end, aluminum is aluminum.

2. Don't airplanes have other flight-critical structural members made of aluminum besides the body?

3. Correct. Lack of maintenance has a tremendous impact on the design of a part. If a part is going to be replaced after a certain number of flight hours, pressure cycles, whatever, it can be designed closer to its limits. Weight is extremely important to aircraft, so they make up for the weight saving with increased inspection, maintenace and/or part replacement.

Part of my job requires that I not only design critical parts, but also write the maintenace and repair procedures for the parts I design.

Since many bikes go unmaintained, it only stands to reason that the parts must be designed to operate in spite of lack or maintenance or inspection. If this is not taken into account, you may get a part that fails.

People apparently jump their folding bikes off curbs (I've never actually SEEN this, but people have written about it in this forum, so it must be true ). If the designer didn't take this into account, you might be getting some stem failures.

Bad design? Maybe.
Not using the right tool for the right job? Maybe.
Bad welding technique and post weld heat treatment? Maybe
Bad material: No!

If a part is designed improperly, you may get a part that fails. By improper design, I mean selection of wrong materials, manufacturing processes, heat treatments, underestimating loads, inclusion of stress risers; I could go on and on.

You wrote in another post about all the handlebar stems that have failed, that you read about in the Mechanics forums. Again, if it's written in a forum, it must be true ! I have actually witnessed ONE single stem failure in my life. It was a steel stem. SO...my observations differ from your research.

In closing, aluminum under stress will behave the same way if it is in an airplane or a bike. It's not a tired argument, and it isn't quantum mechanics. It's a simple matter of proper design, strength of materials and stress analysis.

If you feel my argument was silly, fine. I'll probably post some more items that people think are silly. At lease I've paid for the privilege.

Now, I was able to make my points without once insulting you. Much nicer, eh?