The ability of permanent ferromagnets to resist (or survive) attacks on their permanent field orientations is related to their intrinsic coercivity Hci. In general, rare earth magnets are much more resistant, however, radiation, excessive heat, serious EM pulses, extreme magnetic field pressure as in this case, will degrade magnets. The degree of symmetry is relevant, as highly asymmetrical designs are much less resistant to magnetic field pressure such as in the case of Halbach arrays. I have constructed several Halbach arrays from N35 Neo magnets purchased from K&J magnetics 10 years ago that have lost approx 50% of their force compared to when newly built. Magnet manufacturers can produce a custom run of a high, extremely high, or even ultra high Hci magnets for a price. In past times this was done by increasing expensive dysprosium content, but now there are multiple ways, and I would suggest the Japanese lead in these efforts. I believe Ames Labs patented a form of nitrogen doped carbon which has an Hci that is rather astounding, but to date it is not a stable product.
Can Repelling Magnets Replace the Spring in a Pogo Stick?
91–100 of 149 posts
Re: Can Repelling Magnets Replace the Spring in a Pogo Stick?
#92Earlier quoted context omitted.
I’d also like to know what they meant by “plunges”. How fast did it descend? Was it in free fall?
You can easily tell that it wasn't in free fall, because if it fell 84 floors in free fall and then stopped, the passengers would have died.
It could have slowed down gradually and stopped. The articles I’ve read don’t do a good job describing anything.
Re: Can Repelling Magnets Replace the Spring in a Pogo Stick?
#93Seems like electromagnets could help compensate for distance by drawing more current when far apart, and less when close together. A microcontroller could essentially make the force linear like a spring. Of course, then you need wires hooked up to your pogo, and that might be scary if the microcontroller has a bug (or somehow fails) since you are now essentially hopping onto a railgun.
Alternatively a lever system or non-circular gear arrangement could convert the force from fixed magnets into a linear response entirely mechanically.
...edited for sense
Re: Can Repelling Magnets Replace the Spring in a Pogo Stick?
#94Earlier quoted context omitted.
No, it's linear from basic physics.
Within a certain operating region (stress and strain, i.e. the straight bit on the stress/strain graph), a spring will behave linearly e.g. F = kx . In real life it should be pretty close to linear, but it would be worth checking as I could imagine there being non-linearity or time dependence of a spring under what is probably a decent amount of load being applied quickly and repeatedly.
Yes, that would have been fair.
The electromagnets are also (close to) linear if you look at small intervals.
Re: Can Repelling Magnets Replace the Spring in a Pogo Stick?
#95Earlier quoted context omitted.
YouTube desperately needs an audio compressor feature. Can't imagine why they haven't implemented that yet, it's more or less trivial.
I agree that they should, but it’s pretty reductionist and arrogant to call it “trivial”. There is no such thing as a one-size-fits-all dynamic compressor. You would also need a fairly sophisticated content detection system (don’t distort anything that is music, which is a huge use case on YouTube for example). Not to mention adding _any_ steps to their intake pipeline requires more processing power and data moving t…
Speaking as a reasonably-experienced audio and DSP programmer -- and considering that the feature has existed in just about every home theater receiver for the past 20 years -- yes, it's trivial.
YouTube has the advantage of being able to preprocess the audio track in its entirety, although most implementations work on a block basis and don't need that. A 'night mode' feature would take about one weekend's worth of work from start to finish.
You would also need a fairly sophisticated content detection system (don’t distort anything that is music, which is a huge use case on YouTube for example).
No, you need a button that the user can press to turn the feature on and off. It should default to 'off.' For extra points, make it a slider.
Not to mention adding _any_ steps to their intake pipeline requires more processing power and data moving than you and I will ever touch in our lifetimes.
Compared to the work needed to process the video itself, it would be a total non-issue.
Re: Can Repelling Magnets Replace the Spring in a Pogo Stick?
#96Earlier quoted context omitted.
You can easily tell that it wasn't in free fall, because if it fell 84 floors in free fall and then stopped, the passengers would have died.
It could have slowed down gradually and stopped. The articles I’ve read don’t do a good job describing anything.
If it slows down gradually, it's not in free fall.
Re: Can Repelling Magnets Replace the Spring in a Pogo Stick?
#97Earlier quoted context omitted.
Elevators use simple physical safety systems. Which is why you see headlines like: "Skyscraper elevator plunges 84 floors — and everyone survives" https://www.cbc.ca/news/world/elevator-plunge-chicago-1.4913...
Every link i’ve seen to this story annoys the hell out of me because they don’t explain HOW the elevator eventually stopped. That’s literally all I want to know.
The best book ever for understanding how Elevators work is a wonderful late 20th century work of fiction called The Intuitionist by Colson Whitehead, which was described by its author as what you would expect to happen if you let a child grow up reading elevator manuals.
Re: Can Repelling Magnets Replace the Spring in a Pogo Stick?
#98I’ve often thought it might be interesting to replace the springs in a piano’s action with electromagnets so you could have control over the exact touch profile.
I don’t think pianos typically have any springs, everything is gravity powered with counterweights. The only springiness comes from striking the strings as far as I know. Only the really cheap electronic keyboards use springs. Even halfway decent electronic pianos still rely on counterweights.
I’m pretty sure even really nice uprights (Yamaha U3) have jack springs... maybe I saw the wrong diagram
Re: Can Repelling Magnets Replace the Spring in a Pogo Stick?
#99Can we make an electronagnetic-sprung mattress?
Ignoring other problems mentioned, what would the benefit of such a system be? I suppose it'd be very customizable, but probably expensive (both initial cost plus the cost of the electricity to run it).
Re: Can Repelling Magnets Replace the Spring in a Pogo Stick?
#100Seems like electromagnets could help compensate for distance by drawing more current when far apart, and less when close together. A microcontroller could essentially make the force linear like a spring. Of course, then you need wires hooked up to your pogo, and that might be scary if the microcontroller has a bug (or somehow fails) since you are now essentially hopping onto a railgun.
You don't have to think about buggy software to come up with death scenarios. What if a driver in the other lane is drunk or not paying attention? Another driver could kill you at any moment and there's nothing you could do to prevent it.