> 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).

Various 'copters have been built with counterrotating rotors - the 1st
really successful one was the twin rotor pre WW2 Focke Wulfe FW61 famously
flown in 1936 by female test pilot Hanna Reitsch inside the Deutschlandhalle
sports stadium in Berlin.

    FW61        http://www.germanvtol.com/fockeachgiles/fa61folder/fa61.html
                      http://avia.russian.ee/vertigo/fw-61-r.html

Jolly green giant does this too AFAIK. Also AFAIK it turns by altering
relative speeds of two rotors t get torque differential..

http://www.jollygreen.org/Stories/orgins_of_the_name_jolly_green_g.htm
GGJ search & rescue ('nam and elsewhere)
                    http://www.jollygreen.org/

History of copters with many pictures
                http://www.helis.com/pioneers/


Back to work .... :-)



                RM

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