About this Plan
Contra Gyro. 27in rotor disc diameter concentriic autogyro for .5 to 1cc engines. December 1956 Aeromodeller.
Quote: "No torque troubles with this Canadian twin-rotor egg beater.
Contra-Gyro is the result of curiosity rather than design research! Having built a couple of normal auto-giros, Laurie Ellis was prompted to see what would happen using contra-rotating blades, for it had been noticed that with the normal autogiro one could experience difficulties with certain trim conditions. It was thought that, with one rotor cancelling the torque of the other, it should be possible to trim for left or right turn, or to have straight ahead flight--also the fuselage should not counter-rotate on descent.
The model resulting has come well up to expectations, for one can fly it in calm conditions from art area smaller than a football pitch, and it answers trim in a docile manner with no apparent vices.
This model is not recommended for beginners. All components employ ordinary construction, but accuracy must be assured for the rotor shaft and hub. The whole secret of successful autogiro flying NOS ork the correct angles of rotor shaft and blades.
Rotorhub Assembly. Hubs are shown full size, and the specified 14 s.w.g. wire should be adhered to. Cut tinplate discs to size and drill to accommodate copper or brass tube bearings. Tin the surface of tubes where they will contact the discs; surfaces of the discs; and the root end of the rotor arms. Jig the hub assembly by using a piece of board about 8 in. square, drilling a 1/4 in deep hole to accommodate the bearing.
Mark out position of the rotor arms and insert hub in jig, making sure it is vertical. Slide on one disc and locate rotor an-rie in their proper location, holding in place with pins. (Note.—Dihedral angles, etc., are bent into the arms AFTER the hub is assembled.) Firmly solder the arms in position, using plenty of solder to ensure firm holding. Now slide other disc in position and sweat into place. The second hub is made in similar manner, with blade connectors pointing in the same direction, bearing in mind that, when mounted on the shaft it will be inverted to allow opposite rotation..."
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Supplementary file notes
Article page, text and pics, thanks to RFJ.
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