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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Fri, 29 Nov 2002 14:18:10 GMT
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Original-From:
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Jim Choate <ravage@einstein.ssz.&stopspam&com>
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Viewed:
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3143 times
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On Fri, 29 Nov 2002, pixel wrote:
> 1. pure turbine has to be placed in some kind of tunnel but not exactly
> funnel
> the tunnel has to be as a part of ball (sphere) without hats :)) at the
> upper and the lower side
> because the stream of air has to compact and air cannot escape near the
> blade of rotor or turbine
Bingo.
> 2. lego motor http://peeron.com/inv/parts/2838c01 is the only one useful
> because the new motor has no enough speed
Take a look at some of these micro motors that are being used in the new
mini-RC cars. You can buy a whole car kit, radio, and controller for about
$75US.
> 3. propeler has to be non-lego beacause of weight and shape and stability
A helo tail rotor is your best bet. Wood or a composite is your best bet.
Stay away from -any- metal blades as they are a serious safety hazard in
this application.
> 4. turbine can be weighty so motor can rotate it and keep the speed
> (flywheel)
No, you don't need a turbine. What you're missing is the ratio of the
inlet area to exhaust plenum area and the delta-v of the air flow.
200lb's will get a good lift from 1/4hp.
200lb's weight of hover
------- = ---------------
1/4hp power of motor
> 5. good turbine is cd-disc :)) cut on chords and bent termicaly (it's heavy
> enough) (you need some tools to do it)
Yuck. A CD disk is -way- too big across, and it's aerodynamic efficiency
is insufficient to move enough air. At high air speeds the flat 'blades'
will stall and you will find the flow going down with increases in fan
speed. Your fan shouldn't be more than about 4 inches across.
> 6. for me it's impossible to do lego frame light enough (in fact lego parts
> are heavy especialy axles)
I suspect this isn't true. I'd start with a standard green plate and
eschew the whole idea of a frame, insufficient rigidity in Lego plastic.
> 7. making skirt is very important (i did it from plastic bag) it's a little
> bit hard to do it
Shouldn't be. I'd suspect it's your process, remember you -must- pleat the
corners or the skirt will dump. Hint, the pleats -must- be vertical with
respect to the running board/ground reference frame.
If you're making a tubular skirt then you want to make it in eight (8)
seperate sections. Four (4) straight tubular pieces, use a wood dowel
or a similar form to make. Then the four (4) corner pieces.
--
____________________________________________________________________
We don't see things as they are, ravage@ssz.com
we see them as we are. www.ssz.com
jchoate@open-forge.org
Anais Nin www.open-forge.org
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