Whirligig (oz9729)

About this Plan

Whirligig. Simple rubber helicopter model.

Quote: "THIS direct-lift model utilizes a simple and foolproof counter-rotational system based on the familiar principle of the contest 'whirligig.' Due to the nature of the rubber motor hook-up the two rotors are constantly and automatically in balance with each other, effectually neutralizing the torque element without gearing of any kind.

This model is the 73rd helicopter built by the writer and experience gleaned from the first 72 is incorporated in its construction. Counter-rotation is considered the best approach to the torque problem, due to the fact that as long as some power must be used to offset rotor torque that power might just as well be turned to additional lift. The length of a rubber motor is in any case limited (barring the use of gearing) in a model of this type and it is therefore essential that the best possible use be made of the power that is available.

Two-bladed rotors were used on the original because they may be placed in line with the fuselage making the model a rather flat package and easily portable, a somewhat important factor in cramped city quarters. Three-bladed rotors would probably be okay if you wish to try them. More power would be needed and slightly less pitch would doubtless increase the soaring qualities of the model.

Start construction with the coaxial unit. Study the plans until there is no doubt as to the action of the unit. The motor tube is 1-1/4in diameter and is constructed of either balsa sheet or stiff drawing paper. The thrust bearing is located at the bottom of the tube and consists of a pin-washer-bead arrangement. This bearing should rotate freely but should have very little play..."

Direct submission to Outerzone.

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