Dahon is one of the few bike companies that have their own in-house certified test lab.
https://youtu.be/6iO14EPJ2-U?si=jhRqTKFcPKdnJG8e
They test their bikes and comparison-test competitors' bikes, too.
Some other folding bike companies test their bikes. Brompton:
Strida:
https://youtu.be/iKNo4OIp0H8?si=vjSmckz6yWndVIa6
Since the knock-off/clone folding bike companies never publish images/videos of testing, I'm
guessing they reverse engineer and call it good. No design staff, no computer modeling, no testing: save big money!
The duck comes down, you win $20.
The Curl's hydroformed frame was one of several points Dahon presented in EU court back in 2017 when Brompton sued them for...well, I'm not sure what Brompton's claim was. (Brompton got spanked in that lawsuit, BTW.)
Good to know! I only doubted Dahon's development due to previous cracks on their frames, however those frames were produced 20 years ago (but cracks detected within 10 years), so perhaps their testing was not as good then, but is now.
Video: I think I see one test simulating the failure I had in the seat tube, I think I see cyclic fatigue with a big barbell load simulating rider weight. 100,000 cycles is low, in my opinion, unless they exceeding max design loading. The pedal fatigue testing showed a ton of runout on the pedal axle, but perhaps that was designed into the test, versus a straight pedal axle.
Brompton probably sued for general fold design or aesthetic design being associated with their brand identity, but yeah, you're gonna lose if the defendant's design represents significant improvement. It may get weird with Brompton clones that are dead lookalikes, differing only in the frame being welded and not brazed. But I think the patent has expired so they would have to sue based on the folding design being a "trademark" design.