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Old 03-30-2011, 07:05 PM   #1 (permalink)
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The Aircar thread, a true unicorn or just very inefficient short range transport.

(my first well thought out air car thread dissappeared and never posted ah well, this one gets the point I guess but it simply doesn't sound as wimsical or funny)

The aircar BS has always amused me and the prototypes were always reviewed and hyped like any true unicorn but unlike most unicorns there is a kernal of truth, you could drive this unicorn 20 miles at 25mph or in the case of the air bike 18mph for 20miles. (real homebuilt vehicles)

In either event to bust this unicorn we need the energy capacity of compressed air in a given volume versus pressure and reasons why the air car was only 5% efficient on a good day.

That said the possibility exists for the air car to be usable for some people if we could overcome its dismal efficiency (similar to a model T with flat tires and a stuck carb)

The reasons the air car is only 5% efficient is the pump is only 10-20% efficient on a good day and the motor very similar to the above, add to that the electric motor running the pump is typically only 80%; very sad story but could we do better with scale? I think on the compression side YES, heres why the existing pumps are so inefficient.

1. High pressure means very high tolerances and very high friction
2. High pressure means any small gap between the one way valve and the piston results in a heavy loss of compressed air (which is energy)
3. High pressure air seals always leak a bit and have losses while compressing.

How could we over come this? If it were me I would think using a very tall depth of a liquid to compress the air with a low fluid resistance conveyor to bring the air to the bottom with minimal fluid friction could easily increase this efficiency (with scale) to well over 80%, with a good motor design perhaps 90%, all the air that would be compressed would be deposited into the vessel at the bottom, expansion losses would be minimal, frictional losses could be made minimal with the proper shape, size and speed of the vertical conveyor (ideally you wouldn't want the conveyor to really displace any water while it moved, proper surface shaping could reduce the fluid resistance).

Anyone see any other ways we could make the air car efficient enough (albeat still very limited) to be usuable and reasonable on short distance vehicles? If a large scale system of efficiently compressing air were developed that could move the air car up to 10-20% efficiency (if some minor improvements could be made to the motor) with some limited regenability. Oddly that is the typical trip efficiency of most late model over the road cars.

Anyone think using a fluid to compress air would be very inefficient? I don't see why it would be; bypasses almost ever negative that a normal compressor experiences (and the negatives on a normal compressor grow as pressures grow, whereas with a fluid it would not)

Feel free to add the other strangeness discussed previously into this topic and any new strangeness you want, make my unicorn fly


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