I keep seeing stories in the popular press extolling the wonders of MagLev technology, the superfast trains they make possible and all of the places they could supposedly be used (that is, if anyone was willing to provide the great gobs of money that would be required to build one of these things).
The descriptions I’ve read about the technology say that a MagLev train is levitated a very small distance above the guideway by a magnetic field. I don’t remember the exact distance, but I think it may be only an inch or two. That leads to my question. Would a system like this be able to operate in an area that sees appreciable snow or ice accumulations?
Good question ! My recollection is that the distance is much less than an inch - fractions, actually. The Wikipedia article - http://en.wikipedia.org/wiki/Maglev_train - says 15 millimeters (= 0.6 inch) for a couple of the systems described there.
One of the prototypes has been running in Germany for a few years, and snow (or “schnee”) isn’t unknown there (as well as other prototypes running in some places that I don’t know well enough to know if and how much it snows). So I wonder how they’ve dealt with it - mount a snowplow or ice/ “sleet cutters”, as the old trolley lines used to do ?
For a moment I was thinking that the high-power current that feeds it might generate enough heat to melt the frozen stuff. Then I remembered that many Mag-Lev articles also mention that it’d be so much more efficient once we get the whole super-conducting (of electricity) thing solved, so that there is much less resistance (really, the electrical equivalent to friction in the mechanical world) to the power flow = less heat loss. Further, super-conducting usually needs super-cold to work, so that track - excuse me, guideway - might be a great place for liquid precipitation to freeze. Oh yeah, this is gonna be interesting . . .
…Those who would like to experience “Mag-Lev”, might consider the “people Mover” down in Florida at Disney World. It moves people thru Space Mountain and around that section of the park as entertainment, and something different. It’s been there for years upon years.
And of course snow is no problem in running such a vehicle there…
There is a Magnetic Levitation conference going on now in San Diego. Operational details may be avialable in the proceedings. In Trains is news that the FRA is dividing up $45 million for a pilot project. According to the Washington State Long-Range Plan for Amtrak Cascades, the cost of magnetic levitation new corridor is $20 million to $50 million per mile, while the cost of high-speed rail varies from $1 million to $45 million per mile.
The biggest cost factor with Maglev seems to be the need for a dedicated, elevated guideway something akin to a monorail, that crosses no streets, other railroads, or other obstructions of any type – prohibitively expensive to acquire the right-of-way and construct such a system.
For the question about ice, the experimental Maglev systems I’ve seen on the History Channel have the magnets well under the edge of the guideway out of the way of weather related problems.
Costs? I see that HSR and MagLev ROW costs should be about the same. Both grade separated and separate from other RR tracks. However ROW for MagLev in citys requires new station tracks and not being able to use any existing RRs to get to stations. Power supply should be about the same for the high voltage supply. The problem for MagLev is the requirement for magnetic coils all along a route. Wills there even that much coppper available during construction? The voltages for the magnetic coils have not been defined so there may have to be many more substations (Look at the numer of substations on third rail systems). Next the guideway is much mre massive than crossties that is a major cost. Much more steel probably would be used in that construction. Guideways have rails so no help there. Signal systems will probably have to be different since no contact with guideway happens except with power off. PTC will be entirely different. All these costs add up to the big difference in HSR and Mag Lev.
There are two basic types of maglev – magnetic attraction and magnetic repulsion.
Those low-speed systems used for airport people movers can be magnetic attraction. They require a small air gap along with a fast acting control to regulate the electromagnet on the train so it doesn’t stick fast to the iron in the track. If you have played with magnets and piece of iron, you know how the magnetic force varies in such a way that it is hard to hold a piece of iron just so far away from a strong magnet without the iron being sucked into the magnet. The attraction systems do not require the most powerful magnets, just magnets powerful enough to attract the weight of the train car up to the iron rail across a short gap, but again, these are primarily low-speed systems on account of the requirement to regulate the electromagnet to maintain a precise value for a narrow air gap.
The proposed high-speed systems are primarily magnetic repulsion. There are a number of ways to go about this. The simplest, although perhaps not the most energy efficient, is to have a powerful but plain ordinary non-superconducting magnet in the train, and to have a conductive but otherwise non-magnetic track – say, a sheet of aluminum. When the train moves forward along the track, its magnet induces what is called an eddy current in the track, producing a kind of electromagnet in the track that repels the magnet on the train, levitating the train.
This system works as a kind of electromagnetic flight. A slow speeds you may need rubber tires to support the train. As the train speeds up, it produces a repulsive force, which levitates the train when the train reaches “takeoff” speed. Instead of flying freely about the air using aerodynamic forces, one is “flying” inches to perhaps a foot or two above a track using magnetodynamic forces.
comments: One comment I remember hearing was to the effect that to get a smooth ride that you need to place the magnets as smooth as a road. It would be interested to see what kind of issues one would have with snow and or ice.
One other comment about Mag Lev, you would need to expend energy to levitate before you started moving the train. Steel wheel on steel rail offers the lowest rolling resistance.