If I do not calculate wrongly on my back of envelope, to brake from 10m/s (36km/h) in 10cm you need constant 50g acceleration on the driver... he certainly should feel that. Yes, it is a con.
Meaning no disrespect, I don't see why your "back of envelope" estimate (which you didn't actually share) should be given more credit than the video. Like I said, I think that written description is simply wrong. It wouldn't be the first time a journalist misreported the details of some technology, eh?
I just watched the video again with the playback speed at 1/4 (thanks Youtube!) and at 0:46 ( https://youtu.be/z-h56N_A3rY?t=45 ) when the car hits the bumper I can clearly see the driver lean forward due to inertia. Of course you still need to wear a seatbelt, this isn't magic. (You know on Star Trek how the Klingon disruptors make a person disintegrate, clothes and all, yeah? How does the disintegration process know to stop at the floor? What is it about the interface between boots and floor which stops the disintegration? Could you use that to make disintegration-proof armour?) I get what you're saying. I do.
The point is not that the driver magically didn't feel inertia (he did, and you can clearly see it in the video) it's that the car didn't crumple. The kinetic energy given up by the stopping car went into the flywheel rather than into violent deformation of the physical structure of the car. I.e. it works (if it works at all, I don't deny that it might be a hoax) like a "crumple zone" without the crumple:
> Crumple zones are designed to increase the time over which the total force from the change in momentum is applied to an occupant ...
> The point is not that the driver magically didn't feel inertia (he did, and you can clearly see it in the video)
He clearly didn't experience 50g deceleration, he would have been sent flying through the windshield.
What's more likely is that the car actually did take a lot more than 16cm to slow down to 0 m/s or that it wasn't going at 45km/h. I would bet on the second, the car looks like it's going at maybe 20km/h in the video.
> The kinetic energy given up by the stopping car went into the flywheel rather than into violent deformation of the physical structure of the car.
That's an interesting idea but if it ends up being less effective at protecting the humans inside I don't think most people will choose it over normal crumple zones.
> if it ends up being less effective at protecting the humans inside
Of course. Who cares if you can just reset the flywheel (as opposed to scrapping the crumpled car) if you still have to scrap the people off of the dashboard?
My whole point is that there are devices like this one that may be more effective, given some R&D, but that get neglected.
Let me put forward another, perhaps less physically controversial, example: the "Rolomite".
> Rolamite is a technology for very low friction bearings developed by Sandia National Laboratories in the 1960s. It is the only elementary machine discovered in the twentieth century and can be used in various ways such as a component in switches, thermostats, valves, pumps, and clutches, among others.
> The Rolamite was invented by Sandia engineer Donald F. Wilkes and was patented on June 24, 1969. It was discovered while Wilkes was working on a miniature device to detect small changes in the inertia of a small mass. After testing an S-shaped metal foil, which he found to be unstable to support surfaces, the engineer inserted rollers into the S-shaped bends of the band, producing a mechanical assembly that has very low friction in one direction and high stiffness transversely. It became known as Rolamite.
> The vortex tube, also known as the Ranque-Hilsch vortex tube, is a mechanical device that separates a compressed gas into hot and cold streams. The gas emerging from the "hot" end can reach temperatures of 200 °C (392 °F), and the gas emerging from the "cold end" can reach −50 °C (−58 °F). It has no moving parts.
Now these you can actually buy. They sell little ones that go on the end of an air compressor hose to deliver "spot cold" as it's called. I once emailed a company who makes them to ask what would happen if you set it up so that the cold (or hot) output chilled (or heated) the incoming air, would you get a feedback loop? But they weren't interested.
The vortex tube is less efficient than a heat pump, so there are good reasons not to use it in every potential application, but I feel that there are good applications that go completely unrealized. That's my original point. Just because some cool technology exists doesn't guarantee that it will be used well, or at all.
"back of envelope" estimate (which you didn't actually share) "
If you are interested: going from v to 0 or going from 0 to v uniformly with acceleration in time t is related by v=at. The distance traveled is s=1/2a t^2. Plugging the first into the second gives s=1/2 v^2/a. So a=1/2 v^2/s= 1/2 (10m/s)^2/0.1m=500m/s^2~50g
Interestingly this directly follows from the definition of acceleration and doesnt use anything like Newtons laws.
Looking at the Video, why didn't they just do it in a controlled environment? Some gauges/meter marking and high speed cameras. The time it takes for the stop is in the order of t=v/a=10/500s=1/50s so only one frame in normal video rate.
Cheers for showing your work. But again, in the video, whatever it's faults, you do see a car hit a barrier and not go crunch, yeah?
> why didn't they just do it in a controlled environment?
Well, there is more than one video. The one we're talking about is obviously a public demonstration and not a scientific test. (There was one video that seems to have been removed now that showed a very good and clear demo of the ramp/glass being done at some trade show or convention. that video or others might still be on YT somewhere.)
What about that ramp/glass demo? A glass shatters when the little car thingy hits it, and then another glass doesn't shatter when the flywheel device is active.
And really, I haven't dug into this particular tech too deeply, it could well be a hoax.
But my point still stands, there are lots of interesting and useful ideas that work and get ignored or neglected. Magnus effect rotors, the Tesla turbine, desalinizing batteries, "Aircrete", etc...
I could literally go on all day, just listing the less "woo-woo" stuff off of Rex Research.
