Garami Giro (oz9962)
About this Plan
Garami's Giro. Rubber autogyro model.
Quote: "THIS model is the result of a dare. Too many fellows had told me that it was impossible to make a true Giro. Goldberg had made a Giro, but he used a wing. When the wing was removed it wouldn’t fly, but even without the rotors it flew just as well. So now Goldberg and the others will have to eat their words.
The original of this model was developed back in 1936, when Henry Struck made a stick model following my theory. The stick job flew quite successfully so I followed up with a cabin job which flew even better. It was quite small and in the indoor class B with a 20 in rotor span. Many successful flights and lots of fun were had in the Jefferson Armory in Brooklyn.
This version is a refinement on the original models, and was developed for indoor and outdoor work. Much experimentation and developing was necessary to make this model fly successfully. It took one full day, in which over 100 test flights were made, before the present force arrangements were developed Starting with zero thrust it was finally changed to 10° down thrust This was necessary to overcome the power stall at the beginning of the flight. Torque was quite a problem, but the down thrust gave the model more forward speed which in turn revolved the rotors at a greater speed with increased lift. Another aid for torque is to tilt the rotor bearing wire 5° opposite to the torque. A small pair of pliers will bend this wire very effectively. The bend in the wire should lie directly under the rotor. Rudder effect is quite negligible, but it can be used for very fine adjustments. The center of gravity should be directly in line with the center of the rotor column. To test, remove the rotors and grasp the rotor bearing and check the balance of the model. It should hang absolutely horizontal on a fore-and-aft plane.
Too many designers have the mistaken theory that the rotor blades should be set at a positive angle of incidence. Using this angle of incidence the rotors would move with the trailing edge forward, consequently forcing the model to descend rather than lift. To overcome this condition, the rotors are set at a 3° negative angle of incidence. With this setting, the rotors move with the leading edge forward and the air spills cut under the trailing edge. Any airfoil will generate lift even at settings from 10° positive to 5° negative angle of incidence. It is most important to have the rotors turning in the direction to induce lift The dihedral shown was proved to be adequate, because as the rotors speed up the lift is increased and the rotors tend to flex upward increasing the dihedral.
To flight test the model, stand up on a chair and give the rotor a spin in a counter-clockwise direction. As soon as the rotor is spinning quite rapidly, let the model drop and observe the speed with which it sinks. If the sinking speed is too great, increase the negative angle of incidence of the rotors slightly. The right sinking speed is about the speed of a paper parachute..."
Quote: "Louis Garami's Autogiro published in AIR TRAILS MODEL ANNUAL, 1946. A rubber powered auto gyro that proved the author's theories. This model does not have a wing like so many auto gyro’s do to support lift. The article makes for a very interesting read for those interested in auto gyros. The plans really did not do justice to this design so I redrew it full size. The nose shell makes for a labor intensive carving. The model could use a more conventional nose construction to simplify. Overall, at least to me, this is a very interesting and informative model. Gene"
For a full copy of the 1946 Air Trails Annual, see https://rclibrary.co.uk/download_title.asp?ID=2082
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User commentsI have almost completed my replica of the model. I appreciate some of the minor modifications put on your updated plan, especially regarding the construction of the hub assembly and the dowel inserted to hold down the rotor mast. However I did not like the rear hook arrangement and I substituted a more contemporary aluminum tube. Will send some photos. I would also commend a simple design that appeared in The American Boy compilation by Frank Zaic. It is a baby ROG sized indoor autogyro which is very minimalist in structure and meant for indoor use. It is essentially wingless, except for small surfaces held some inches out from the motor stick, and covered only at the tips set to counteract torque from the six inch high pitched prop. set with washout right and washin left to counter act l torque. Very nice design and simple but very cleverly conceived. This is close to done as well. Thanks for your fine site.
PaulHelman_Illinois - 12/04/2018
Good afternoon Mary, some photos of a build from your plans: OZ9962 Garami Gyro [model photo & more pics 007].
TrevorT - 19/12/2018
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