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146 AIRCRAFT ENGINEERING June, 1931 A Gyroscopic Instrument with an Ingenious Mounting and Fluid-Friction Drive of General Application NE W aircraft instrument has been produced utilised in the new mounting by constructing the Th e recovery, or re-erection, from any displace b y Mr. Pollock Brown which, it is claimed, roto r with fan shaped blades which constitute an men t can be accelerated, so as to give almost combines the functions of turn indicator unbiased drag on the speed, and, therefore, a instantaneou s rectification, by temporarily tighten and fore-and-aft level. The details of the "P.B . definite slip in the fluid drive of the bearing : thus ing up the bearing drive. For this purpose a small Deviator, " as the device is called, can bo seen in when the spindle axis is deflected the rotor axis is pea ball is let into a recess on the axis of the driving th e accompanying drawing. no t immediately coerced to follow. . ball and can be pressed against the bearing surface The principle of the gyrostat has always formed Th e performance depends on the rotor energy (a b y the axial thrust of a small rod passing through an irresistible attraction to inventors and others function of its moment of inertia and its angular th e spindle, which is hollow. The push button when developing apparatu s for direction indicating, velocity), the fit of the universal bearing in relation seen a t the bottom of the figure operates this. This device may be very useful when changing direction bu t the ideal of a frictionlcss universal mounting to the lubricant used, ard the speed of the slip in, say, a vertical sense. is extremely difficult to attain. It has, however, combined with proper proportions in design. It led to many ingenious devices to counter the pro Th e particular type of instrument illustrated is cessional troubles which arise from the frictional arrange d for a drive from the engine speed-indicator torques, all leading to complex constructions and flexible shaft without interfering with that instru sacrifice of reliability, in accuracy if not in ment . The diameter of the deviator flange is 4 in. functioning. and the weight about 25 oz. Thre e Degrees of Freedom Teste d in Flight When a directional indicator is required only as a I n actual flight the deviator appears to carry out supplement to the magnetic compass, the exacting its designed functions satisfactorily, subject to the demand s of the above ideal can be considerably tw o reservations indicated later. modified as deflections on a reasonable time base I t was tested in a Desoutter cabin monoplane, become acceptable. A universal coupling drive to an d although it was impossible to find any clouds, a th e gyroscopic rotor at once suggests itself but ver y fair indication of its performance could be unfortunately the follow-up of the rotor axis to arrived at by throwing the machine about, and then an y deflection is spiral in form, as well as being levelling up again by means of the instrument, rapid, and so is useless. All development has, withou t looking at the ground. will thus be realised that the rate of follow-up of therefore, been aroun d a gyroscope wit h " tw o degrees I t appears that care must be exercised under th e rotor axis depends on the amount of deflection of freedom," which can only show th e rate of deflec two conditions. which governs the torque, and this can be so small tion in one plane by the precession at right angles Firstly, should the machine be sideslipping with a s to allow the actual amount of a reasonable t o that plane, against springs to control the sensi one wing down, but otherwise maintaining level deflection to be observed. tivity and dash pots to eliminate oscillations. flight, the deviator will read exactly the same as Th e new form of mounting with "thre e degrees Th e Instrument Described for a good turn ; that is i t will move along one of the of freedom" adopted in the P.B. Deviator con Th e P.B. Deviator for use in blind flying is one horizontal bars. There is no great likelihood of stitute s its own drive to the rotor with great particula r development of the new mounting, the thi s trouble being met with, as it requires some care simplicity and is applicable to man y other purposes. features of which should be clear from the fore to sideslip without the nose going up or down— I t also provides an exceptionally slow and radial which will be instantly shown by rise or fall of going and reference to the accompanying drawing. follow-up, or erection, from deflection in any th e indicator Th e rotor axis is extended to carry a small disc direction. Secondly, should the indicator be found to be in faced with a yellow resin on its extremity. This The rotor, as can be seen from the illustration, is one of the sectors, i t is advisable to correct in two disc is immediately behind cross wires, fixed and the mounted on a single cup and ball-bearing on the movements . For example, should the indicator casing, which was slightly convexed so tha t the disc end of a spindle and is driven by the fluid friction be in the top right-hand corner, it should first of all remains the same distance from them at all angles. of tha t bearing. If balanced it will, therefore, align be brought back to th e vertical line by means of the An y deviation of the aircraft, represented by the its axis with tha t of th e driving spindle. aileron and rudder controls, and then brought down casing and cross wires is at once indicated by the I t is well known that the frictional resistance to the centre by means of the elevators. Other disc, which temporarily retains the previous line between two surfaces in one direction is almost wise it has a tendency to " hunt, " and confusion of flight, being of a diameter calculated to represent eliminated if a definite slip is caused in another ma y arise as to precisely what is happening to the 10 degrees deflection. direction, say, at right angles. This has been machine . If used in conjunction with a cross-level and compass the instrument seems capable of doing all tha t is claimed for it. Historica l Congress Th e second International Congress of the History of Science and Technology is being hold in London from June 29 to July 3, 1931. The Honorary Secretar y is Mr. II. W. Dickinson, and the official address. The Science Museum, South Kensington, London , S.W.7. Th e Congress originated with the Comite Inter- . national d'Histoire des Sciences founded at Oslo on Augus t 17, 1928. This body meets annually and organises a congress every three years, of which thi s is th e second. It is held with the co-operation of the Comite International des Sciences Historiques an d the two other Societies, the History of Science Society of America and the British New- comen Society for the Study of the History of Science and Technology. The inaugural meeting will be held at 3 p.m., on Monday, June 29, and durin g the morning sessions papers will be read . in the following groups: (1) The Sciences as an integra l part of general historical study; (2) Historical and contemporary inter-relationships of the physical and biological sciences; (3) Inter-dependenc e of pure and applied science. Subscription rates to the Congress are: for member s of an y of th e four bodies mentioned above, £1 ; others, £1 5s.
Aircraft Engineering and Aerospace Technology – Emerald Publishing
Published: Jun 1, 1931
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