I question the short video as to whether this is normal gyroplane rotorblade, or even helicopter rotorblade movement. Being filmed in black & white indicated it was filmed many decades ago. Anything more recent would have been in color.
In the youtube comments below the video, someone identified this video of a BO105 helicopter. Made in Germany, info I found indicates the rotorblades as being fiberglass, and the four blades were hard-mounted to a hub bar that has no hinges.
I had suspected the blades in this video to be wooden, and were shown w/ such extreme movement out at the tips to be a result of their wood construction as well as being driven hard by powerful engines. I thought possibly this was a piston powered helicopter, and that the evident motion out at the tips to be engine torque pulses. But, they were powered by turbine engines.
Kind of like the end of a whip, or a human line of rollerbladers holding hands, and then "cracking the whip", resulting in forces that no one can maintain a grip out at the end, flinging the last one or two people off. No hinges means the blades themselves react to engine forces, collective commands instituted by the pilot, and maybe even wind shear encountered while flying.
We fly a teetering rotorblade on our gyros. It also isn't powered by the engine. I suspect our rotorblades do not exhibit such flex as this video shows. Also, every helicopter I have seen in person has hinges for each blade. Consequently, wouldn't video of a hinged blade show very little movement compared to this example?
Engine powered, (possibly old design) fiberglass rotorblades hard mounted to the hub bar mechanism that doesn't allow the rotorblades to flap?
Aluminum rotorblades, I'm guessing (since I'm no expert) would show a plank (the rotorblade being videoed) being steady, because the teetering hinge of a two-bladed gyroplane. I've also have no idea of how an aluminum helicopter rotorblade would look, but also suspect it would look like the gyroplane rotorblade in flight. Since it has hinges for up & down flapping, as well as lead-lag ones, those hinges would probably prevent such violent movements out at the tips.