Why This Maglev Train is Unstable

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Real Engineering

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So why the hell would anyone use option 1? Only thing I can think of is that having the electromagnets on the underside of the rail weights offer better protection against the environment, but literally everything else seems worse.

ImaSpacePotato

You used the wrong colors for the repulsive forces. The magnets are supposed to be aligned

Mulakulu

The solution is to mostly use pulling force with push force being there for more stability

amazingamx

Something relevant is Earnshaw's theorem that basically guarantees instability in a system of point charges. You need some stabilizing component somewhere in the system. Ever wonder why passive magnetic bearings aren't really a thing? This is why. You need something like an electromagnetic control system, a physical point of contact, or something more exotic like a superconductor to stabilize the unstable system.

Scipiworld

The pulling approach has 2 big strengths: safety and wear.

Safety: If the levitation fails, you have a train with no wheels sliding along a rail, applying break force pretty much at every point touching the rail. The sideways guides will still work to keep the rail on track.

Wear: if the levitation fails, you are rubbing steel against steel. The brittle and expensive magnets are pulled away from the contact point, and are way less likely to break.

That push configuration looks like it's just begging to derail at the slightest amount of sideways force, with nothing to keep it going along the rail.

Yes, option 1 is unstable, in the control system sense. Option 2 is also unstable, but with less control measures to counteract the instability, or to deal with the consequences of failing to stabilize. Option 1 seems built with instability in mind. Option 2 seems like it's been included to talk about the physics/engineering, not as a fully developed transport solution.

melineeluna

I never considered how inherently unstable the pulling approach is. TIL

TheBlueye

Shouldnt the repulsive forces diagram show matching polarities against each other?

lukapaka

Just a quick point: The Maglevs you show in the shorts are all German Transrapids, not Japanese trains.

FlowNeffets

"Repulsive forces"

Sounds like my aura😎

the_defaultguy

When I was a kid I came up with an idea of electromagnetic repulsion train. When I learned those exist I became really sad because I wasn't fast enough to invent it

orestchudnovets

I've thought about this and even theorized about repulsive levitation rails with a stronger attraction rail (but set farther to equilibrium the repulsion) in the middle to act as guidance, only to find Chinese engineers have beaten me to it with retrofitted SAFEGE suspension train.

thestudentofficial

“Aww, it’s not for you… it’s more of a _Shelbyville_ thing” 😂

Vtarngpb

As a non engineer, I'm gratified by the positive comments by obviously knowledgeable people.
Maglev is still the safest - can't derail,
Still the cheapest to operate and maintain,
Still the fastest, cruising at 300 mph,
Still the quietiest,
No moving parts except the doors; and maybe the sink faucets.
Chicago to New York - 3 hours
Chicago to Seattle - 7 hours
Total automation possible

HighHolyOne

While repulsion has its advantages, magnets will decay faster if continuously repelling. They last a lot longer as magnets when their magnetic forces ate always pulled into alignment.
That one reason pull is better then repel.

LG-qzom

What about the lateral force needed for cornering "the centripetal force" how it is generated, or just the inward tilt of the rail is sufficient?

JushuaAbraham-sjxl