Engineers of the forum please prove me wrong!

[piterx]

hi guys...

i'd start saying that i aint an engineer so i don't know anything about maths physics and stuff like that...

since i was a kid i had this thing in mind...

it requires a little bit of imagination but i'll try to explain it the best i can:

let's suppose that all the blue pins are the north pole of a magnet

let's suppose that they can be at different distances

let's suppose that the angle can vary

do you think it's possible that the truck holding the black connector, facing to the magnets with the same pole so the force would be repulsive, can move along the rails?

and if it would...what would it do if the rails describe a huge circle so every segment is almost straight? (so it has the less curvature possible)

please prove me that it doesn't keep moving for ever because i'm about to buy 200 magnets and a lot of connectors to test it XD

[sergiuparaschiv]

Two issues:

1. Friction. If the magnets don't provide sufficient acceleration to overcome the friction generated by the wheels turning on the rails then it will eventually stop.

2. Magnet decay. In time (very long time - tens of years probably) regular magnets loose their magnetic properties.

In more technical terms, Second law of thermodynamics. ("Equivalently, perpetual motion machines of the second kind are impossible.")

So unfortunately your perpetuum mobile won't work :)

Edited December 3, 2013 by sergiuparaschiv

[piterx]

well...if it can keep spinning for ten years in my room it would be cool anyway :D

mine wasn't an attempt to make a perpetual motion lol

anyway the model was just a concept...of course i'd reduce the friction of the wheels a lot someway and the magnets wouldnt be so small :P

[Carsten Svendsen]

I believe you would have to make the spacing between the rail magnets 3 studs instead of 1, then, on the wagon, you put a magnet on each end so that one magnet is on top of a rail magnet and the other one is between the rail magnets.

You could do this with the current 1 stud spacing but I think that the magnetic force would be too strong and slow the wagon down instead of keeping it rolling.

[tibivi]

This would be awesome when it could have worked, but, like sergiuparaschiv said, the friction of the wheels will stop the truck.

The magnets shouldn't be a problem i think, when you use permanent magnets,

It was a great idea though,

Tibivi

Ps, i had an idea like that (not a car/rollercoaster but just a moving stick), but with lego magnets, the axles have too much friction on the technic beams. It keeps moving for about 12 seconds, so it kind of failed. But i still have it.

Edited December 3, 2013 by tibivi

[Tech-nick]

In theory your truck would be lifted (less weight on the tracks) a bit, but there is no force to put it in motion.

Magnets with same poles facing each other of course pushes them apart but the next magnet on the track is pushing against the trucks magnet in equal force --> tracks magnets cancel each other (no propulsion, only lift).

Edited December 3, 2013 by Tech-nick

[piterx]

I believe you would have to make the spacing between the rail magnets 3 studs instead of 1, then, on the wagon, you put a magnet on each end so that one magnet is on top of a rail magnet and the other one is between the rail magnets.

You could do this with the current 1 stud spacing but I think that the magnetic force would be too strong and slow the wagon down instead of keeping it rolling.

yeah man i believe that too!

this is just a concept, the spacing, the angles, the wheels used are just theoretical at the moment :P

i really need to try it with those few magnets i have at home...

This would be awesome when it could have worked, but, like sergiuparaschiv said, the friction of the wheels will stop the truck.

The magnets shouldn't be a problem i think, when you use permanent magnets,

It was a great idea though,

Tibivi

Ps, i had an idea like that (not a car/rollercoaster but just a moving stick), but with lego magnets, the axles have too much friction on the technic beams. It keeps moving for about 12 seconds, so it kind of failed. But i still have it.

cool! would you post it :)? im curious!

i tested this once when i was a kid...it kinda worked but it's so long time ago that i don't even remember how good it was...i need to re do it again

[quilkin]

It's not just about the friction; there will be a point between each pair of magnets on the rails where the repulsive force of the first would equal the repulsive force of the second. So the truck would get stuck there, once the momentum of your first push was lost by friction. I don't think the train truck would move any further than it would without the magnets, in fact it could be less.

Nice design of track though

[piterx]

It's not just about the friction; there will be a point between each pair of magnets on the rails where the repulsive force of the first would equal the repulsive force of the second. So the truck would get stuck there, once the momentum of your first push was lost by friction. I don't think the train truck would move any further than it would without the magnets, in fact it could be less.

Nice design of track though

i was suspecting something like that!

is there anyone who owns enough lego magnets to test it XD?

[D3K]

It is a great thought, but in practice I don't think it would work..

It like Tech-nick says.

The magnetic field of your standars magnet moves around it, from one pole to the other, as seen in this image

Unfortunately it doesn't beam out positive (or negative) force in a straight line from either pole..

[aol000xw]

Something like this can be achieved, but not with this geometry. Also it won't be like droping the "car" on the rails and see it moving. More in the lines of giving it a good push and see how it loses momentum slower than usually but coming to a stop after a few... seconds, don't think it could achieve minutes.

[Tamas Juhasz]

Tech-nick wrote the essence:

"In theory your truck would be lifted (less weight on the tracks) a bit, but there is no force to put it in motion.

Magnets with same poles facing each other of course pushes them apart but the next magnet on the track is pushing against the trucks magnet in equal force --> tracks magnets cancel each other (no propulsion, only lift)."

And: You have friction. A moving vehicle in the track generates "friction power" (not only force, power!), which became mostly heat. You don't have any power source for putting power in the system, so you want to generate the power for "fight against friction power" from nothing. This would be a perpetum mobile, as someone said before me.

You can make a magnet tarck, which levitates the vehicle, but you have to put power in the track or in the vehicle for propulsion.

Edited December 3, 2013 by Mbmc

[aol000xw]

As long as he does not try a loop he can have a "car" moving up on a slope. There is already energy in the magnets . Adequate magnets and geometry are required and depending on the design steel instead of a magnet must be used on the "car". It is not free energy, just a clever way to use the energy already used to create the magnets. Also all the friction created by the Lego elements might be too much depending on the strength of the magnets.

Using the magnets to gain potential energy to later transform it into cinetic energy won't net enougth to move our "car" back to the starting point and achieve perpetual (while the magnets last) motion.

Perhaps with no atmosphere at 0ºK using some superconducting mats to achieve an almost frictionless path back to the starting point something like that could be achieved. I think it is out of reach of our beloved Lego no matter how many neodymium magnets you throw at it

For the "climbing" the magnets must be setup in such a way that the magnetic field is stronger when going up the slope (closer magnets) That way the steel is continually pulled upwards by the magnetic fileds. Think of it as carefully placed magnets alternating at both sides of a track, closer every time. It's a neat trick for a GBC using steel balls, but you then need something to move the balls back to the starting point

Ok guys here you go

[piterx]

so it kinda works...

i should definitely try it when i get back in my hometown where i have the magnets :P

[DrJB]

There is one way to make this work ... but you have to continuously keep moving/rotating the magnets so as to create a magnetic 'traveling wave' onto which the train would ride. This is in essence how some of the high-speed levitating trains work. The catch here is that, while the train may seem to move with little/no effort, you must provide a mechanism to move/rotate the magnets ... or back to one of the earlier posts, the 2nd law of thermodynamics cannot be ignored/violated (conservation of energy).

Edited December 3, 2013 by DrJB

[Lakop]

Complicated.

H

[DrJB]

Complicated.

H

Not really .... but may require some tweaks

Conceptually, the idea is to attach each magnet to a gear, then have all those gears synced/phased properly, and all driven by the same chain ... Not that easy, but absolutely doable.

Edited December 3, 2013 by DrJB

[MrTekneex]

In my opinion, if properly sized, it works!

[aol000xw]

Lego Magnets

Feel the power in those words.

[Lipko]

It is not free energy, just a clever way to use the energy already used to create the magnets.

Actually, I think the energy is "added" to the system by moving the attracting parts away from each other. Sure, if a magnet was never next to the iron, no energy is "added" in that sense, but as soon as they start to approach each other, you'll have to put energy to the system to move them apart again.

The emphasis is there, because the motion is an essential thing here.

Edited December 3, 2013 by Lipko

[skppo]

Angling the magnet won't angle the repulsive force in a way you might think. Magnets can't do free work for you. In order for it to push

you must first increase the potential energy by pushing an object into the field against it. Think of it like gravity. A rollercoaster won't

accelerate down a hill unless you first push it up there.

Edited December 3, 2013 by skppo

[Seasider]

You actually wanted to ask physicists too and not just engineers (I'm the latter)

Something should be theoretically possible based on the other comments you've had so far.

The issues you'll have for maintaining forward motion are the 'dead zones' between magnets ... Or just make sure the 'trucks' magnet can only ever "see" one magnet. Then there's the issue of friction of the truck on the track .... And not forgetting our other friend drag

There should be lots of stuff on the internet about how things like maglevs work to give you ideas

Good luck !

[Front]

There is no way to make a perpetual motion machine, it's as simple as that. If a magnet passes another magnet, the net work done by each magnet is zero. You can't create energy out of nothing. It is a consequence of the second law of thermodynamics.

Erland

Part Designer, now in TECHNIC team

[aol000xw]

Actually, I think the energy is "added" to the system by moving the attracting parts away from each other. Sure, if a magnet was never next to the iron, no energy is "added" in that sense, but as soon as they start to approach each other, you'll have to put energy to the system to move them apart again.

The emphasis is there, because the motion is an essential thing here.

The magnetic field just transforms potential/cinetic energy. There is a cost to putting the steel ball in the right place so yes when setting up the ball you are adding the energy that will be used. Setting up the magnets just efines the magnetic field, does not add energy to the system. that can be used by the ball, altougth it adds potential energy to the magnets.

Angling the magnet won't angle the repulsive force in a way you might think. Magnets can't do free work for you. In order for it to push

you must first increase the potential energy by pushing an object into the field against it. Think of it like gravity. A rollercoaster won't

accelerate down a hill unless you first push it up there.

Thats why steel instead of a magnet is used in the moving object, you don't want to fight against repulsive forces. Just benefit from ingreasingly attracting ones.

You actually wanted to ask physicists too and not just engineers (I'm the latter)

Something should be theoretically possible based on the other comments you've had so far.

The issues you'll have for maintaining forward motion are the 'dead zones' between magnets ... Or just make sure the 'trucks' magnet can only ever "see" one magnet. Then there's the issue of friction of the truck on the track .... And not forgetting our other friend drag

There should be lots of stuff on the internet about how things like maglevs work to give you ideas

Good luck !

No, it needs to be under stronger influence as it travels trougth the magnetic field. So no just one magnet at a time....

This will show it more clear....

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[JM1971]

There is no free lunch in psychics, that's what people tell me when I think about doing perpetual motion contraptions.

Someday I want to get a handful of neodymium magnets and use them for a extreme off-road suspension car.