Russell McMahon wrote:
>
> > Is it possible to have 4 fans on the 4 corners of a platform facing
> down/up
> > and spining them in separate directions ie the fans diagonaly opposed
> > spining the same direction and the fans opposite spining opposite.  The
> > direction and control could be achieved varying the speed of 2 fans.
> >
> > I appreciate the difficulties in getting some control but it should be fun
> > trying to keep out of its way.
>
> It certainly is.
> But getting fans with "opposite" blades would be harder. Most fans of a
> given type will have the same rotation. I have not ever thought about which
> way fans turn but odds are the whole industry does it the same (Murphy
> says).
>
> Have a look at the gizmo copter to see what they do.
> Note that the motors draw 96 amps :-)
>     Gizmo copter home page
>                 http://www.gizmocopter.org/
>     Copter
>                http://www.gizmocopter.org/elj-contest-200108/
>     ERPS home page
>             http://www.erps.org/
>     Join ERPS list
>                 http://cube.erps.org/email/join.html
>
> Also, with 4 distributed fans I feel the affect of all one way torque may be
> less (but this sounds like heresy).


Umm, isn't the torque issue only valid upon one
axis? If you have a helicopter with 2 "fans" they
don't have to spin in opposite directions, provided
the fans are located apart from each other (like a
Chinook).

Vertical designs like the Osprey use fans that rotate
in the same direction. :o)

Contra-rotating blades are only really needed when
you have both fans on the one axle, which is perfectly
valid for some designs.

I have fiddled with some designs for a little "spy in the
sky" type unit, with two fans, one front and one back with
a small combustion engine (vert shaft) and a lightweight
toothed belt to drive both fans. Very light. Simple RC
servo operated vanes under the fans give yaw and pitch etc.
gets rid of most of the helicopter stability problems and
would even be usable in buildings etc. I wish I had more
time, sigh.
-Roman

PS. Gizmocopter appears to have standard rotating props,
ie all 4 in same direction. Most of the RC props i've seen
have been clockwise.

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