6402Views38Replies

# Can a magnetic propulsion system be achieved Answered

Earnshaw's theorem states that a collection of point charges cannot be maintained in a stable stationary equilibrium configuration solely by the electrostatic interaction of the charges. This was first proven by British mathematician Samuel Earnshaw in 1842. It is usually referenced to magnetic fields, but originally applied to electrostatic fields. It applies to the classical inverse-square law forces (electric and gravitational) and also to the magnetic forces of permanent magnets and paramagnetic materials or any combination, (but not diamagnetic materials). Earnshaw's theorem has no exceptions for unmoving permanent ferro-magnets. However, moving ferromagnets, certain electromagnetic systems, pseudo-levitation and diamagnetic materials are areas to which Earnshaw's theorem doesn't apply and thus can seem to be exceptions, though in fact these exploit the constraints of the theorem.
Can we develop a safer cleaner transportation method that involves electro magnets that can propel cars using the city's grid to adjust the power on the street or road to move cars. similar to  famous movies vehicles like STAR WARS(c) Repulsor Lift(c) technology or The MATRIX(c) Ships OSIRIS?

Tags:

## Discussions

what about a dc motor with a few well placed electromagnets that constantly switch polarity to oppose a track of electromagnets on a exterior circle that also switch polarity according to the interior track + to - to + to - repeat repeat all that would be required is the initial spark correct then if done right could it not power it's self and possibly be perpetual until the parts wearout please don't steal my idea for military or selfish purposes unless you need to save life that would wear on the cricket in my head lol

It's not perpetual motion. You must be supplying external power input to constantly switch polarity in order to drive the system. A system of static magnets like that is a well-known non-functional "perpetual motion" device.

hmmm well maybe i'll get it right eventually my other idea is permenant magnets with mechanical triggers and spring levers to constantly flip the magnets but electromagnets i believe would generate more rpm

That system will still loose energy to heat.
Even though the train/vehicle hovers above the track, there's an electrical interaction between the magnets and the vehicle.
That interaction causes the magnetic elements of the system to increase in temperature. It's a bit like electromagnetic friction.

In some instances, this causes huge loses in efficiency. (like in electric motors.)

Train systems have an easier time because the magnets on the track don't need to constantly be in use and they have a chance to cool.
Thermal loses cause disorder in the magnetic vectors of the crystalline structure of the magnets.

still cooling the system sounds like such a small hurdle

Try doing the math. Work out the eddy currents due to the moving magnets, plug in the resistivity of the metal, and use Ohm's law (P = I2R) to determine how much heat is being produced, which will tell you how much power dissipation (cooling) you will need.

Kelsey,
I know why you're being defensive about this, but Sessha isn't being belligerent about it. I mean... maybe you didn't mean to come off harsh, but you did kinda. I'm guilty of that a lot, so i kinda understand. Just sayin.

Sessha, cooling systems are among the least efficient systems that exist. If running 1 volt through an electromagnetic coil causes a 1 degree increase in the coil, the cooling rig that removes that single degree increase can use as much as 10 times the energy to get rid of it (depending on the cooling rig used) as the energy that went into the thermal increase.

People each have their own ideas as to what's the best cooling system, and how you're constrained by your design matters.

While i dislike the Petroleum industry (they do actively interfere with technological innovation which would make them obsolete), there are solid reasons as to why we do things the way we do them.

Straight out, Electric motors are some of the least efficient motors on the market. The induced magnetic fields, which are what causes the movement in any electrical motor (AC or DC), cause alot of heat, even in copper.
Using permanent magnets doesn't change that, but you are correct in the idea that you can combine permanent magnets with cooling systems some what more easily then you can with more traditional electrical motors.

Do you ACTUALLY know what you are talking about ?? Modern DC drives are easily >>90% efficient.

Link one credible reference that shows that they have an electric DC motor that is greater then 90% efficient, and I will retract my statement. I've personally not seen anything credible stating any motor achieving greater then 80% efficiency, electric or otherwise.

Practically speaking, electric motors are more efficient then internal combustion engines, but it's because they don't have to idle to continue running, unlike an internal combustion engine (that is to say, an electric motor can turn off while not running).

Electrical motors show significant drops in efficiency when moving a load, and when they first start moving. That's ignoring adverse environmental effects and just paying attention to the effects of operation conditions.

Parker Traction motors make a good example

http://www.parkermotion.com/mobile/ParkerTractionMotBroch_WEB_4.20.10.pdf

Their headline figure is 95%, you'll see from the efficiency graph, the end to end efficiency doesn't droop below 85%.

Its not hard to find drives with similar characteristics

Your original claim that "electric motors are amongst the least efficient motors on the market" is just completely wrong, utterly wrong.

First, I said credible reference.
That's a manufacturer's website. It's not much more reliable then a TV commercial.

Let me explain why i specifically stated a Credible source:
People have built machines that resemble perpetual motion machines. It's not hard to take a motor under idealized circumstances and really skew efficiency ratings. If you combine that with bunk science, it compounds the problem.

Second, it's not wrong if you consider operational constraints.

There are very few situations where a DC motor is ran continously through idealized parameters. Usually, the vehicle is dragging around a heavy battery, plus what ever other load it has to worry about (Like passengers or cargo).
People don't use statistics for Internal Combustion Engines that operate under ideal parameters, why should we skew the analysis of DC motors by only using their idealized performance evaluations?

For the record, batteries are not 100% efficient either. If you're trying to consider the actual energy efficiency of a vehicle, you really should take these losses into account, because an internal combustion engine generates it's own electricity after the initial spark is produced.
Since we're talking about it, Losses are not simply cumulative. A battery operating at 80% efficiency in a system that's using a magic DC motor that's 80% efficient (5% higher then third party verification systems have ever tested), results in a system that's only 64% efficient. In practice, an efficiency this high won't happen.

A very brief analysis of electrical vehicles in the US, for those wanting to be lazy:
http://www.fueleconomy.gov/feg/evtech.shtml

And for those who have the money to blow on a PDF:
http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=932141

I wil admit this much: i did overstate it somewhat. They aren't always the most inefficient solution, but they're rarely the most efficient option available.

You're back pedalling furiously. I work with a electo-magnetic design specialist who assures me 90% + efficiency is now routine. He designs them for a living, quite often for ultra high speed, very small size drives, but also things resembling wind turbine motors.

We weren't talking about end-to-end efficiency, your analysis is pretty accurate there, but your blanket statement that "Electric motors are some of the least efficient motors on the market"

Steve

I'm not back pedalling.

If you commit to using a Direct Current Motor in any design, you're committing to one of two constraints.

Either, you're comitting to cumulative losses in efficiency due to inclusions of batteries or other powersources, or you're committing to losses through use of a transformer and tethered to a wall socket.

The end result is the same: Your efficiency goes down.

Let me say it again:

Those losses are a natural part of using that component.

That means any cumulative losses in efficiency can be directly attributed to the motor, since you wouldn't be experiencing those losses if you committed to a different component.

Here we go again, you were condeming ALL electric motors as "inefficient" NOT the drive trains, or the end-to-end effiiciency.

Your blanket statement is IMPO, drivel.

Fair enough.

If counting inherant losses in efficiency that occur as a natural consequence of using a Direct Current motor is drivel I'm comfortable letting my drivel stand.

People are free to use their own judgement.

Ummmm... Steve is a practising professional engineer in this field with 30+ years experience. He knows extremely well how to calculate and measure efficiencies in complex systems.

Citing manufacturer specification sheets is a credible reference, probably the most credible you're going to find, since those specs are aimed at the actual users of the device in question. Next you're going to tell us that we shouldn't believe the data sheet for a 555 timer because "it's no better than a TV commercial."

The efficiency of a complete vehicle, which happens to include an electric motor for propulsion, is obviously going to be much less than ~90%. That's because there are many systems, linkages, etc. between the motor and the vehicle's movement. You made a statement about the bare motor efficiency itself, which was incorrect.

i was thinking more along the lines of a air funneling system to cool without a powered cooling system possibly doing it in a way that would allow air to flow around the magnets and lightening the weight of the craft or whatever and I wonder if you could possibly get power from the skin of the craft because when i was in the army i worked on chinooks and all helicopters store a static charge from flying through the air that's why we had to ground them before ground fueling or million dollar aircraft go boom didn't mean to tick anyone off it's just a theory i was putting out

Air cooled systems are great if you have to worry about weight, but, in terms of actually cooling things down, they're not good at all.

Air is not very dense, especially when you compare it something like a metal coil.

That lack of density means there's less material to absorb the energy off of whatever needs to be cooled.

Now, the amount of air increases relative to the speed that the vehicle is travelling, but, the accumulation of heat in the magnets does to. If we consider wind drag, this is even more true.

This can be side stepped a little bit by increasing the relative surface area of the magnet. This is usually done by adding aluminum fins to things but you can't do that to a moving part very easily or effectively, and at a certain point, you'll outstrip the air's ability to dissipate heat quickly enough before materials fail.

There's a reason y most things go to liquid cooling eventually.

i see i always just figured it was a corporate plan to get money or something i thought that if you condensed the air that it would work better than a liquid cool system all im familiar with is fins and scoops

To answer the question of the OP, yes, we can use electromagnets to make cleaner transportation, but we (the US) won't.

Transportation schemes that use Magnets over a certain strength are illegal in the US. Officially this is because they're bad for pace makers. Unofficially it's complete BS meant to protect the interest of Oil companies in the US.

Monorails and super high speed trains both use a combination of Permanent Magnets and Electromagnets to move heavy loads extreme distances at extreme speed. Japan and europe both have used Monorails and high speed electric trains to good effect.

We're more likely to develop flying wing shaped blimps instead of trains.

Hmm. Not really. Mag-lev concepts have been around for close to 50 years, but not deployed due to the costs. After the French TGV system virtually set the standard for high speed trains, and it runs on conventional track, the need for mag-lev's VASTLY more expensive components more or less died out.

Also: diamegnetic levitation. Got to love the videos of the levitating frogs and stuff.

Step out of the car and watch as your belt buckle slams into the road :P

That answers a question and is the reason I'ma go steal several MRI machines, grab a pile of fire extinguishers and meet me at the lair...

Hee hee, until you look at the "related" videos and see the "X-thousand-pound MRI magnet being lifted by a crane" ones.

I didn't say how I'd steal them. I just said I would... Details are really best left vague here...

This is killerj, you have too many letters in there, he's just sort of vacant

Um, "vaguancy," as Prince Humperdinck's bishop might have said...

While you can lift/levitate things using electromagnetic forces, they usually require a base or object which would remain on the ground (such as a maglev rail or a magnetic/supermagnetic base) so even if you can do it, it would only work in certain areas where such an object is constructed. While it may be possible and even efficient in transportation over a previously constructed "road" (such as maglev trains), for the type of levitation as in many sci-fi movies/shows it would be extremely impractical unless a new and improved form of magnetic propulsion is created.

What is the text-lift (from Wikipedia I assume?) for, and do you understand it?

It's not at all practical, that's why it looks good in films...

L

i did it to reference Earnshaw's theorem so that viewer can have a basic understanding of what it is i'm asking so i do completely understand otherwise i wouldn't post it

I don't see how you are applying it to a transportation method that involves electromagnets. Your details are not given.

L