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A ducted fan approach may work.
Ducted fan hovercraft have one or two big fan blades on the back that push
the craft forward, but a duct takes some of the air and uses it to fill the
skirt. This is probably the "lightest" design approach. Direction
(including reverse) is controlled by vanes on the very back.
There is also the famous British hovercraft that had a HUGE thrust fan in
the center of it. The duct looks similar to those nuclear plant tower
hourglass shapes. Although, this design (in LEGO) would be very heavy and
the thrust probably wouldn't be enough.
In either case, one might consider using a thin baseplates for the deck.
- Rob
----- Original Message -----
From: "Steve Baker" <sjbaker1@airmail.net>
To: <marco@soporcel.pt>
Cc: <lego-robotics@crynwr.com>
Sent: Tuesday, November 26, 2002 5:00 PM
Subject: Re: "real" LEGO Hovercraft ? (with/without batteries/RCX "onboard")
> Marco Correia wrote:
>
> > 3) Is there a LEGO-only way to generate enough air flow (pressure) ?
>
> The experiments we've done with the helicopter suggest that you can
> generate some pretty impressive volumes of fairly slow moving air -
> but high speed/low volume is hard.
>
> The RDS insect wings that we used on our helicopter work really well,
> but I don't think they'd be much use for a helicopter unless you had
> a funnel to take the large volume low speed air and speed it up into
> a narrow stream that could inflate a hovercraft's skirt.
>
> I've seen toy hovercraft that worked well with very small motors.
>
> > One solution to "trap" the air underneath the unit is to build a LEGO
> > framework (as light as possible) and then use plastic film (that used to
> > keep vegetables fresh etc) to create something like the bottom of an
> > hovercraft.
>
> Hmmm - interesting.
>
> ---------------------------- 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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On Tue, 26 Nov 2002, Rob Limbaugh wrote:
> A ducted fan approach may work.
>
> Ducted fan hovercraft have one or two big fan blades on the back that push
> the craft forward, but a duct takes some of the air and uses it to fill the
> skirt. This is probably the "lightest" design approach. Direction
> (including reverse) is controlled by vanes on the very back.
Basic LCAC design. The air that drives the skirt is -not- derived from the
direction fans but rather from the turbine input plenums (those babies
will suck as much air in just a few 10's of sec. as goes through your
entire house in year). If you took air from the vector fans you wouldn't
be able to fill the skirt until -after- you started to move, which
requires the skirt to be filled. And reverse is -not- derived from vanes,
but rather a PTO with a reverse gear, turbines only turn one way. Most
LCAC's -won't- go backward, they rotate around their 'center of thrust'
(as compared to center of gravity), which does use the vanes.
The ones that -used- to ply the English Channel were always favorites of
mine. It's a pity I'll never get to ride one now.
--
____________________________________________________________________
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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Rob Limbaugh wrote:
> There is also the famous British hovercraft that had a HUGE thrust fan in
> the center of it. The duct looks similar to those nuclear plant tower
> hourglass shapes. Although, this design (in LEGO) would be very heavy and
> the thrust probably wouldn't be enough.
That was the SRN1 - the worlds first working full-sized
hovercraft - which (amazingly) didn't have a skirt.
You can see a picture of it here:
http://www.hovercraftmodels.com/hovercraft_history.htm
---------------------------- 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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On Tue, 26 Nov 2002, Steve Baker wrote:
> That was the SRN1 - the worlds first working full-sized
> hovercraft - which (amazingly) didn't have a skirt.
Several of the original hovercraft didn't have skirts, they were the
running board sitting on the ground.
There is a simple childrens science experiment to demonstrate the effect.
Take a sewing thread spool (the old wood kind work best) and put a straw
down the middle. Then blow down the straw, the spool will float.
--
____________________________________________________________________
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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Hi Rob :)
> A ducted fan approach may work.
Yes, I *think* that's the only way.
> There is also the famous British hovercraft that had a HUGE
> thrust fan in the center of it.
That's my first approach. I'll deal with motion next.
> The duct looks similar to those nuclear plant tower
> hourglass shapes. Although, this design (in LEGO) would be
> very heavy and the thrust probably wouldn't be enough.
100% LEGO yes, but I'm planning on using LEGO (maybe ZNAP at first, then a
mix of Technic) as the "wire-frame" and then use plastic film to "fill" the
all thing.
mc.
PS: A cool thing would be if LEGO became interested in this, and could build
custom light ducted propellers and/or an electric ducted air turbine...
erm... and then release it as another Mindstorms Expansion or as a complete
(working) Hovercraft Technic set ;)
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