GB767996A - Supporting model aircraft or the like in a wind tunnel - Google Patents

Abstract

767,996. Wind tunnels. ARMSTRONG WHITWORTH AIRCRAFT, Ltd., Sir, W. G. Aug. 9, 1955 [Aug. 18, 1954], No. 23999/54. Class 4. [Also in Group XXXVIII] Apparatus for supporting an aircraft model or the like in a wind tunnel includes two struts extending into the tunnel and movable in unison or independently by means outside the tunnel in a direction at right angles to the tunnel axis, and also in unison along the tunnel, the struts supporting the model through means for rotating the model about its axis. In Fig. 2, the model 14 is attached to a strain gauge balance 15 through a sting 16. An electric motor in the balance 15 can rotate the model in roll. Pins 22 on the struts 12, 13 engage apertures 23, 24 in the balance 15, the former being elongated. The struts slide on guide bars 18a-18d and are raised or lowered by lead screws 21a-21d, which are driven by electric motors 19 and 20. The whole apparatus is mounted on a frame 25 slidable on rollers 26 in channel members 27 parallel to the tunnel axis 10, by an electric motor 28 and lead screw 29. The lead screws 21a and 21b are connected to a transmitter 45 and the lead screws 21c and 21d to a transmitter 46. These drive repeaters at a console, Fig. 6 (not shown) with two dials, one showing the height of the front fulcrum pin 22, and the other the difference in height, this difference being found by a differential gear, Fig. 4 (not shown). A potentiometer 32, Figs. 2 and 3, is attached to strut 12, the wiper 33 being on the strut 13. The voltage picked off is compared with that derived from a manually set potentiometer 35, the comparison being used to operate a relay 37 controlling the rear strut motor 20, so that the setting of potentiometer 35 determines the relative positions of the struts, and hence the incidence of the model. To raise or lower the model, the front motor 19 is operated, the rear strut then following up. Figs. 3 and 5 show mechanism for causing the model to pivot about a selected point in its length, instead of about the forward pin 22. A lever member 56 is pivoted to a fixed support at 60, and a slot 58 in the lever engages a pivot 61 on a slider controlled by a gear 62, which is operated by a transmitter in the console responsive to the difference in heights of the two struts, so that lever 56 is angularly adjusted in accordance with the incidence of the model. A pin 65 on the lever 56 engages two slotted levers 67, 69, each pivotally mounted on a carriage 72, 73, and adapted to operate micro-switches 70a, 70b and 71a, 71b. If the model is altered in incidence, lever 56 is rotated, displacing levers 67 and 69. The appropriate micro-switches are closed to actuate motors 19 and 28, Fig. 3, to adjust the model so that the point on its length corresponding to the position of pin 65 on lever 56 is returned to its original position. Transmitters 45 and 83 actuate gears 74 and 75, Fig. 5, traversing the sliders 72 and 73, providing a follow up effect. The transmitter 83 also actuates a repeater 82 on the console indicating the axial position of the model.