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内容記述 |
The light sources were fixed to the root of the undercarriage strut and the Oleo cylinder, and their motions during the drop tests of a single-seater fighter measured by the Optcgraph. From the record of the displacement, the acceleration and the forces on the aeroplane, Oleo, and the wheels were obtained by the method of graphical differentiation. Our conclusions with respect to the shock-absorbing motion of the Oleo under-carriage fitted with high pressure tyres (3.9 atm.) are as follows: (1) The effective height of drop is 93 to 88% of the apparent one, even though the aeroplane is stripped of the fabric on the wing and on the fuselage. (2) Tyre deformation starts and goes on earlier than that of the whole undercarriage. (3) At the instant of maximum acceleration, the tyre deforms most, while the Oleo deforms with max. velocity. Max. acceleration occurs much earlier than the max. stroke of the whole undercarriage. (4) In this type of Oleo, which is combined with a spring with initial compression, a shock occurs at the instant the oil-spring stroke begins. (5) The stroke of an Oleo of constant orifice at the time of maximum load may be taken as constant, regardless of the magnitude of the load. (6) In the drop tests of a small aeroplane, stripped of all fabric, the work done by air resistance amounted to 5% of the total, while the energy dissipated by it was 10% of the total dissipation. (7) The ratio of the energy absorbed by the tyre to that absorbed by the Oleo is about 4:6, that by the tyre increasing as the height of drop increases. (8) The energy absorbed by the Oleo is dissipated to the extent of 93%, which amounts to 84% of the total hysterisis. The tyre dissipates 26% of the energy absorbed by it, which amounts to 16% of the total hysterisis. (9) In the earlier stage of the shock-absorbing stroke, the tyre absorbs the greater part of the energy, while in the later stage the Oleo absorbs the greater part. (10) The efficiencies of the Oleo itself and of the Oleo undercarriage were found to be high compared with those of other types of Oleo undercarriage. (11) From test results, the discharge coefficient for the Oleo orifice worked out to 0.63. This value may safely be used in designing this type of Oleo. (12) The calculation for the motion of the shock-absorber, assuming it to be a spring, gave a maximum acceleration value that agreed fairly well with the measured one, but not the depression value. (13) The result of the trial method of calculation, given the load-deformation curve of the tyre, agrees well with the result by measurement. (14) The calculation was extended to the case when there is wing lift. For the same vertical velocity at the instant of landing, there exists approximately the relation n'=n-k, where n': shock load factor when the lift is taken into account, n: do. when the lift is neglected, k: the ratio of the lift to the total weight of the aeroplane. (15) Design procedures are given in detail for Oleo gears of both constant and varying orifices. |
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