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Aviation History
1937
1937 - 0418.PDF
IOO FLIGHT. FEBRUARY 18, I93; The Hafner A.R.III, Mark II, has a very short take-off run (about two yards) and climbs remarkably steeply. The engine is a 90 h.p. Pobjoy Niagara III. (Flight photograph.) THEORETICALLY it should be possible to suspend the blades of a rotating-wing aircraft on wires, pro vided that the blades were stable in pitch, and if some means could be found of getting the blades started on their circular path. It is rather the stone-on-a- string problem in a slightly different form, or perhaps one would be nearer the mark in comparing it with the cow boy's "building a loop" in his rope. In the type of rotor head on which he has been working for several years Mr. R. Hafner has made use of this principle, and the very light rotor control of the A.R.III gyroplane is a direct result of suspending the blades on tension members of small diameter which can twist under relatively small torsional loads. In this way friction is greatly reduced and the pilot's controls become as light as those of a fixed- wing aircraft. The torsionally elastic suspension of the blades is by no means the only interesting feature of the Hafner rotor, A NEW R01 First Details of the Hafner Gyroplane : " Finger-light" Control : Improved Rotor Efficiency but it does form the basis for the rest of the mechanism, which is shown in the sketches which illustrate these notes. Before describing the mechanical details it may be of assist ance if the fundamental principles are explained briefly. The rotor blades are attached to the head in the orthodox manner, with horizontal hinges which permit the blad:'i to "flap," and vertical hinges with friction dampers for permitting the blades that slight freedom to alter their spacing to which one has become accustomed. The actual attachment of the blades to their hinged forks is, however, by way of the " wire" referred to above, so that in addi- On the left is the rotor hub with one of the three yokes and the hinge bolts which take their bearings on the inner and outer flanges of the hub. On the right are the three interlapping yokes in place on the hub. The larger arm of each yoke is slotted to accommodate the hinge pin of the shorter arm o the adjacent yoke and vice versa.
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