Subject:
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Re: "real" LEGO Hovercraft ? (with/without batteries/RCX "onboard")
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Newsgroups:
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lugnet.robotics
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Date:
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Sun, 1 Dec 2002 18:08:43 GMT
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Original-From:
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Steve Baker <sjbaker1@^avoidspam^airmail.net>
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Viewed:
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978 times
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Rob Limbaugh wrote:
> Brushless DC motors, such as those used in PC cooling fans, won't generate enough power, even if the voltage is increased. This is because they actually have a switching circuit that changes polarity of the electromagnetic coils.
>
> I've gotten a small (less than 1 square foot) piece of foam board to hover using an older 12v fan with brushes and two 9v batteries in series.
>
> Doesn't the thrust fan also have to overcome air leaking around the edge of the fan blades and the thrust fan shroud?
(Do you mean the "Lift Fan"? The "Thrust Fan" is the one that pushes
the hovercraft forwards.)
In the case of the lift fan, yes - because the pressure of the air in
the skirt is higher than the air above the fan, it'll leak out anyway
it can - and around the edges of the lift fan is a possibility.
Keeping the duct close to the tips of the propellor is an obvious
thing to do to improve this.
There is a lot of subtlety to understanding the airflow around the
tips of propellors. Propellor tip design is an important matter
for airplane props. In the case of ducted propellors - I'd presume
that a squared off tip that closely matches the shape of the duct
would be the best design.
---------------------------- Steve Baker -------------------------
HomeEmail: <sjbaker1@airmail.net> WorkEmail: <sjbaker@link.com>
HomePage : http://web2.airmail.net/sjbaker1
Projects : http://plib.sf.net http://tuxaqfh.sf.net
http://tuxkart.sf.net http://prettypoly.sf.net
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