View Full Version : Maglev VS Air Hockey
04-20-2003, 06:31 AM
Every time I read an article about maglev trains one thing that always sticks out is how incredibly costly the tracks are. Why not use a thin layer of compressed air to lift the train and reduce friction instead? (I'm thinking in terms of the train using a diesel powered on-board air compressor of some sort to lift and propel the train)
04-20-2003, 07:09 AM
Because trains are really really heavy. You'd have to be pumping a pretty righteous amount of air through the thing to keep it off the ground.
04-20-2003, 07:50 AM
Compressed air has a buttload of lifting power if used properly though. especially when used between two smooth surfaces.
04-20-2003, 08:50 AM
My guess would be that with a compressed air system you have more points of failure and a much more complicated system for the transmission of lifting power. You would not only need to wire the track with electricity (to power the lifting fans or air pumps) but also with ducting to blow forced air along the track in an even manner. That's alot of moving parts and things to break down or go wrong. If you add in tertiary factors like noise, heat management ect and it's practically impossible.
With maglev you just need electricity wired down the length of the track and it has few if any moving parts. Much less prone to malfunction I would think.
04-20-2003, 11:28 AM
I'm thinking in terms of putting on the blowers on the train not the track. The track would just be a smooth half-round concrete channel about ten feet in diameter resembling a big water slide. The train would be cylinder-shaped an inch or two smaller in diameter than the channel.
04-20-2003, 11:41 AM
As far as I know, there have been experiments being done on hovercraft trains, especially in France. IIRC, the reason why this path was abandoned later on was much more banal - the things were awfully loud.
I don't have a cite for this handy, but I'll google around.
04-20-2003, 11:46 AM
Ah, I got it. The project was called Aérotrain, conducted by French engineer Jean Bertin.
04-20-2003, 11:51 AM
Hell, I forgot the link: http://aernav.free.fr/English_Index.html . The project was going on during the 1960s.
The Aérotrain is said to have reached an average speed of 418 kmph and a peak speed of 430 during one test in 1974, but research was discontinued later on because of TGV competition and noise pollution.
04-20-2003, 02:34 PM
Another good idea killed by politics.
Low friction isn't the only advantage of maglev. They also have superior acceleration and deceleration because they don't rely on wheel friction to transfer power. I don't think an air-powered vehicle can compete with the acceleration of maglev. Acceleration is more important than speed for short trips, like the 19-mile track in China (the first maglev to be operational). Superior power also means it can handle steeper slopes.
I rode a maglev at a world fair in Yokohama about 15 years ago. I remember being surprised at the high (but brief) acceleration - more like a car than a train.
04-20-2003, 03:56 PM
Politics is a fact of life. Besides, all this train did was move people around. Why is improving their lives a "good idea" and inconveniencing others "politics"?
The noise issue doesn't surprise me. Once you lift the train on an air cushion, the only way to move it forward is with a propeller or jet engine. The sound would be like standing next to a runway while a plane was taking off. The TGV is comparable in speed, and much quieter; sounds like the right choice to me.
(I once heard about a project in the U.S. that built a turbine-electric locomotive. Basically, this was a jet engine (instead of diesel) turning a generator, power then going to electric drive motors. This was also cancelled for noise reasons; it sounded like a 707 going through your back yard.)
04-20-2003, 05:00 PM
According to the site the acceleration was excellent and noise could be reduced with a ducted fan. For moving around within a city maglev is probably better becase of the quiet, however, the maglev track is still very expensive so for longer trips air cushion would be much more economical.
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