Can someone explain why this can't be real?

General Questions
#1

Can someone please explain why this can’t be real.

You have to watch the video to see what i’m talking about, but it’s an apparent perpetual motion machine that runs on magnets. Apparently this thing can keep on spinning forever. Yes it may break eventually and the magnets may eventually become demagnetized but that isn’t what would negate it from being a PM machine. It seems to overcome friction and keep going and going. I know that can’t be physically possible.

So, I’m sure it’s fake, i’d just like to know what the actual physical flaw is. Usually I can tell. Perhaps this array of magnets does not really cause any forward force, as implemented in the video.

#2

First and foremost-It’s a video. We have no way of checking to see if there was a separate power source, and we have no way of knowing how long it kept spinning.

#3

Either there’s a power source hidden in or under the device, or they just didn’t show it long enough for friction to slow it down. There’s not a lot of other options.

#4

Well i was hoping someone could tell me “it won’t work because of __” rather than telling me it’s fake. I know it’s fake, i’m sure there’s a power source or whatever. I’m not fooled by it.

#5

In the middle of the video, when he is showing the development of the machine, there’s version that uses someone’s hand to move the “repeller” magnet in and out of the vicinity of the machine. This provides the force to move the magnets, just like pumping a swing with your legs. Clearly, the machine itself can’t provide that force, since the force required is equal to the force imparted to the rotor (and that doesn’t even take into account any losses).

#6

I would bet money it’s a hidden battery. It looks to me like it’s starting to slow just before he stops it as if someone had just remotely cut the power.

#7

I think you’re right. It’s not clear how much force is required to hold that bar down on top (and to pick it up), and even if you put a weight on it, the momentum of the spinning wheel would need enough force to lift it up. More weight = harder to lift.

In the video it looks like it just falls down and simply being there is enough, but there would be some repulsion, and that would lift the bar up to some degree, which would minimize the magnetic repulsion.

Thanks, this satisfies my curiosity.

#8

There is clearly some mechanism at the bottom of the wheel, flicked by the rotor arm - maybe triggering an electromagnet to boost the rotation.

#9

It won’t work because it violates the First Law of Thermodynamics, which states that energy can neither be created or destroyed. All perpetual motion machines founder on this one. When shown a “perpetual motion machine”, you don’t have to determine the gimmick. Knowing the First Law is enough. Nobody has ever found an example where this law was violated.

#10

I would be interested to know why the sliding vertical rod needs to be in such a long thick bearing block. There would be lots of room for a simple helper electromagnet, simply one triggered by the passing magnetic field, either a reed switch or a Hall effect sensor would do it.

My ideal has always been to build a machine like that, but one capable of leeching enough power out of stray mains electrical field in a home. Sadly, whilst there might be enough about to cause a bit on hum in one’s HiFi, one would need a miraculously well engineered mechanism to be so powered.

#11

I know that, but there are specific ways why PMMs fail. I know it’s fake, I know it’s gotta have an external source of energy, and I know it violates thermodynamics.

But why/how does this specific device fail? That’s what I was looking for. I think I got the answer I wanted. It’s a though experiment.

#12

The video suggests that it works by the bar magnet repelling the magnets on the drum. There’s a cam that lifts the bar magnet at just the right time, so it can start repelling the drum magnets again for each rotation.

The energy that causes the horizontal magnet to repel the drum magnets is released through gravity. As the bar magnet falls it gets closer to the drum magnets, and the angle of the drum magnets results in magnetic forces causing the drum to turn. That is, the bar magnet pushes the drum magnets, and the energy of the pushing comes from falling.

The problem is that the bar magnet has to be lifted again for each rotation. The energy required to lift the magnet is the same as that released by the magnet falling.

BTW, what’s impossible is a machine that allows you to draw energy from it perpetually. It is not impossible, in theory, for something to move forever without an external energy source. For example, a planet could, in theory, orbit a star forever. In real life there’s always friction, so even this type of perpetual motion is impossible in practice. But what most people mean by “perpetual motion machine” is a machine that moves forever while allowing you to draw energy from it. This violates conservation of energy, so it can’t happen.

#13

I wouldn’t even jump to ‘motor’ or ‘battery’ or ‘fake’. It’s just that it only ran for a few seconds. The thing might only run for an hour un-aided. At my work we have a price gun that, when hung back on it’s hook, will rock back and forth for about (I swear) 1-2 hours if no one touches it. It’s not a perpetual motion machine, there’s just not much friction between the gun and the hook. But there is some and it eventually stops.
In grade school we had to make 'PMM’s for science class. I whipped something up in 10 minutes that morning (because I forgot about the project). It ran for 3 hours until someone from another class touched it. It’s not difficult to make something with very little friction.

Have that guy show us that there’s no extra power sources on his PMM and then stick a web cam on it. You’ll probably find out it stops spinning in less then 24 hours.

ETA, have him try to extract (useful) energy from it and I’ll bet it stops in a few minutes, even just trying to light an LED.

#14

Also you said yourself that the magnets will demagnetize. That in and of itself would make it not a PMM because putting new magnets on it would be an input of energy to keep the system moving. If it’s a PMM even though you have to replace the magnets, then my car is a PMM even though I have to put in more gas from time to time.

And how come these videos always have that weird music playing over the top of them?

#15

I think this might be the answer to the OP. More precisely: Each time the device makes a revolution, it gains energy from gravity and the magnets on the way down, and loses energy pushing the bar back up. The loss is slightly more than the gain (as in all alleged perpetual motion devices) but the loss is SO slight that it takes a long time to be noticable.

The system gets its initial energy from gravity when the guy first releases the pin. That first pull is then distributed over the lifetime of the device until it finally winds down (due to friction of course; why does the OP think that it has overcome friction?). To poke a hole in my explanation, or to make the demonstration more believable, all he needs to do is to release the pin when the bar is in the BOTTOM position.

#16

No-The question actually is “Why would anyone consider this to be real, as opposed to videos with dancing cats or flying houses?”

#17

It can’t be real because we’re in a dream, and the dreamer doesn’t know it’s supposed to stop spinning.

#18

Oh, come on. It’s a legitimate question. The OP was wondering what, specifically, was the trick in this specific machine. That doesn’t mean they thought it was real.

#19

I don’t think that’s correct.

The machine appears to accelerate at the beginning. If all the initial energy were from the potential energy of the raised magnet, I would expect it to just slow down and stop.

So there must be an external power source of some kind. It could be quite a lot of things, but I think the simplest one is that there’s a spring inside the drum that is wound up and unloads when the pin is released. That explains the initial acceleration for a few turns and we’re not shown a long enough video to see it wind down.

#20

It will just slow down and stop eventually. Every push from a magnet requires a push toward the magnet first, from the previous one. But friction will eat up that push each time, and eventually it won’t be enough to get to the next one.