Gyro-copter (oz10184)

About this Plan

Gyro-copter. Free flight sport model, for Cox Pee Wee power.

Quote: "Whirlybird experts will go off like rockets after reading this one. But have fun with Pee Wee chopper.

Model helicopter competition for the Hiller award has never received the support it deserves. One of the reasons is that most builders of these machines never get them to fly. This, because no one really knows 'how' they fly; what the force arrangement is. Presuming them to be helicopters is the first giant step to failure. The model 'copter in its present form (top mounted engine) is a machine of extreme functional simplicity (a gyroscope being lifted by a small, high-RPM prop). This hybrid has but one form of stability: gyroscopic force; the force arrangement is prop-lift and gyro-stability. Igor Sikorsky spent months wobbling about a few feet off the ground, probing the complexities of helicopter stability; this involved complex maze of aero-gyrodynam-ics has no bearing 'on, nor can be applied to our present torque-reacting models.

After trying for almost two years to get a so called 'torque-reaction' helicopter to fly, we put it down, and took a long, hard and we do mean hard, look at this ornery bird. First, it was a poor excuse for a helicopter with the small engine propeller doing all the lifting. Second, with the main rotors doing no lifting it was neither a torque-reacting helicopter nor a co-axial one. What manner of machine was it then, that we were trying to fly? The answer is, we were trying to 'fly' a gyroscope! The gyroscope of course being the non-lifting, spinning, tip-weighted rotor blades.

At this point we pushed aside the whole business of 90° gyro-precessive, reaction, cyclic pitch-control, gimbal hung props, et-al and decided that these machines flew only as long as gyroscopic force held them on a level plane. Once displaced, the flight was over.

So, considering the main rotor as a gyroscope we built the gyro-copter; watching it in smooth auto-rotative descent from a 200 ft altitude seems to bear us out on the above premise.

We would like here with the permission of ye editor to say a few words 'over the air' to our co-conspirator in helicopters, Dick Quennan. Months ago, Dick, discussing our upside-down 'copters, you noted that yours went over less readily with added tip weight. This bugged me with the gyroscope idea that got me flying, (feel kind of let down finding our machine being really no helicopter at all).

If you've found nothing better so far Dick, and might want to give this gyro thing a spin, I would like to note what I think makes it work. Dismiss all aero and cyclic considerations from rotors, make them flat, operate them at zero for highest RPM - with blade against stop at optimum zero (slight positive) have tip weight below rotational plane giving it force to hold blade hard against stop (no flipping). Light wire rotor mountings and sloppy rotor to mast bearing seem to add up to a smooth spinning gyro. None of these things noted interfere with autorotation. It comes down fine.

Building: In building the gyro-copter it must not be assumed that since the rotors don't lift that a so-so job on rotor hinges, blade stops, etc is good enough. A first rate job is still needed here. They must be alike and free acting for autorotation. The rotor mast should be carefully fitted to spin freely in fuselage. But, when we get to the rotor-to-mast bearing, it's got to be 'sloppy'. Note mast detail drawing; don't try to 'improve' here. In building, cut out rotors first, plain outline, no airfoil, three coats of dope, weighted down on flat surface between coats, and left that way until fuselage is built. At this time alumi-num tube for rotor hinges should be care-fully cemented to top of rotors (Ambroid for this) and left to dry solid while making engine mount and rotor arms..."

Gyro-copter, MAN, January 1960.

Direct submission to Outerzone.

Supplementary file notes

Article pages, thanks to RFJ.

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