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Aviation History
1909
1909 - 0831.PDF
DECEMBER 25, 1909. THE GYROSCOPIC BALANCING OF AEROPLANES. MARMONIER'S GYROSCOPE PENDULUM. EVERYONE acquainted with the action of a pendulum knows how it hangs straight down if freely pivoted or swings into an oblique position if the frame carrying the pivot moves abruptly to one side. The general nature of the reactions associated with a pendulum are all perfectly straightforward to the non-technical mind, and any general scheme in which a pendulum is employed as a regulator can in consequence be quite easily under- stood. Most people are also familiar with the gyroscope, at any rate in the form of a child's spinning top. The actions of a gyroscope are, however, less commonly understood, and for that reason it is necessary to briefly point out one of the leading phenomena associated with its action. A gyroscope, which essentially consists of a fast-spinning fly- wheel, has this peculiarity, that when its axis of revolution is tilted up or dipped down, the reaction brought into play by this applied force introduces a tendency for the axis of revolution to swerve to the right or left. This apparently violates the ordinary straight- forward idea of action and reaction being equal and opposite, and we do not pur- pose to go into any explanation of the why and wherefore of the phenomenon, it being sufficient for our immediate pur- pose to draw attention to the peculiarity. If a gyroscope replaces a pendulum bob, there is a combination of the two effects, which naturally results in a modi- fication of the normal pendulum action, and on this scheme Louis Marmonier has based bis idea for the automatic balancing of aeroplanes. M. Marmonier points out that the pendulum alone is unsatisfactory for the purpose, because, although its weight tends to keep it vertical, it does not, after being disturbed, definitely resume that position until after it has made a series of oscillations. Furthermore, M. Marmonier realises that the centrifugal force of a heavy pendulum would be a source of great danger in turning. A simple gyroscope alone M. Marmonier considers would be insufficiently powerful to perform the work required even if operated through a relay mechanism, and would, he considers, further be liable to a change in the direction of its axis by insensible degrees, which would nevertheless alter the neutral course of the flyer. A very heavy gyroscope, M. Marmonier points out, could not be used because of its weight and the force required to drive it, and especially because its inertia would inter- fere with the necessary manoeuvres of the flyer. But, although neither the gyroscope nor the pendulum will alone accomplish the object desired, M. Marmonier considers that the effects sought can be obtained by a combination of the two principles. In the Marmonier apparatus two fly-wheels are mounted on a short horizontal shaft which is attached at its middle point to the lower end of a vertical rod. The whole forms a pendulum which can oscillate only in the plane containing the axis of the wheels and perpendicular to their forces. The pendulum rod is prolonged above its axis of suspension, and its upper end carries a vane parallel to the faces of the wheels. The function of the vane will be explained later. The gyroscope is driven by the main engine through some suitable transmission mechanism, which does not disturb the pendulum action. A gyroscopic pendulum of this con- struction, moving in a straight line per- pendicular to its plane of oscillation, tends always to remain absolutely vertical, even if subject to violent lateral displacements. The only force which tends to make the pendulum swing is one of angular displacement, that is to say, when the aeroplane to which it is fitted changes its course so as to rotate the apparatus about its vertical axis. The effect of this torque is to swing the pendulum either to the right or to the left, the direction being determined by the direction of rotation of the gyroscope fly-wheels. The inclination or swing of the pendulum will increase with the magnitude of the original disturbing torque, and will also be inversely pro- portional to the length of pendulum. It will, therefore, be a maximum when the pendulum length is zero, which, of course, would mean that the apparatus was a simple gyroscope. Directly the disturbing couple ceases to act the pendulum returns to its vertical position. Another fact to be taken into consideration is the natural centrifugal force on the pendulum apparatus considered as a pendulum alone, and the result of this is that the direction of rotation given to the gyroscope fly-wheels is such that their gyroscopic tendency is to swing the pendulum inwards when the aeroplane is travelling over a circular path. The natural pendulum action is, of course, to swing outwards, and consequently the opposing forces can be made to produce any desired resultant. The function of the vane attached to the top of the pendulum rod is to provide an automatic compensation for variations in the direction of the wind. If the wind blows obliquely to the line of flight, its pressure on the vane, which normally travels edge-on to the wind, is such as to create an initial tilting force on the pendulum, and thus to modify to a proportionate extent the effect of the pendulum and gyroscopic action. The precise means by which the device could be made to operate upon the controlling members of a flyer would, of course, require working out independently for each particular machine. A Flying Ground at Osborne. establish there a branch of their works for the construc- FORTY acres of ground at Osborne have been leased tion of flying machines, which will be tested on the by Messrs. Saunders and Co., of East Cowes, who will , adjoining ground. ( 833
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