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Aviation History
1935
1935 - 0243.PDF
January 31, 1935. Supplement ientto ffi$0*^ FLIGHT ENGINEERING SECTION Edited by C. M. POULSEN No. 1C8 (Voiu0™f X) 10th Year January 31, 1935 SOME NOTES on the PARIS AERO SHOW By H. J. POLLARD, Wh.Ex., A.F.R.Ae.Soc. (Concluded from page 95 of December 27, 1934, Issue) Last Month Mr. Pollard dealt with Metal Construction. This Month he has chosen for his Main Subject Retractile Undercarriages, but he also has something to say about Magnesium Alloys THE extent to which wing flaps and retractile under carriages had been embodied in designs were other items on which information was sought. In regard to split trailing-edge flaps, only two or three machines were so fitted (notable among them being the Heinkel He 70); the mode of operation was in no case clear, but, on the other hand, some information was to be obtained on the operating mechanisms for undercarriage retracting gears, and some of these were most interesting. Most of the types exhibited are illustrated in Figs. 1 to 7. Figs. 1 to 4 (taken from UAeronautique) show four different systems of retraction developed by the Potez Company. Fig. 1 illustrates the method used on the Potez 54. Each wheel is held in a fork F which also forms the housing for the shock-absorber system. This fork is held by rear struts which are articulated at A, and their upper half forms the base of a pyramid with apex at P. Retraction is effected by pulling on P by means of the hydraulic ram and cylinder R. In the case of Fig. 2, each pair of wheels is carried on a separate axle which is mounted on bar B, which in its turn is articulated at each of its extremities on absorbers A and A1. The system is braced by strut T. Retraction mto the cavity is effected by pulling" on T via a long screw, and nut. In the first part of the lifting the horizontal movement forward x is much greater than the vertical lift y. which, incidentally, permits of altering the relative posi tion of the wheels in relation to the C.G. of the aircraft— I A J?' the distribution of the loads between the wheels and the skid can be varied. In trf" 3 sJlOWS ^e arrangement on Potez types 532 and 533. bv a °ASQ two racuus rods are secured at A on the oleo leg y a cardan joint; the top of the leg is articulated on ring B, which is moved along tube T by means of a cable, and retraction is effected by pulling on B. Fig. 4 illustrates the method used on the Potez type 56. The wheel of each half of the complete undercarriage is held in a fork which is secured by rearward struts B, the latter being articulated at A on the fork. The upper extremity of each strut is mounted on a frame on a slide C which can move along an oblique tube T. Retraction is effected by pulling on C in a manner similar to that shown in Fig. 3, except that a chain is used in place of the cable, and in this case it would seem that power greater than manual effort would be necessary to operate the mechanism. Another retractile undercarriage on view was that de signed by Messier; this, as well as being demonstrated on the Messier stand, was also embodied in the Bloch 21 iB. The design appears to be very similar to that given in Fig. 1 above, except that the pyramid arrangement of struts is not employed, the push taking place directly at point of articulation A (see Fig. 5). Both in this and the Potez 54 design rubber cord is used to " break the joint." Power for retraction was supplied by electric motor and oil pump. In both cases, also, locks were provided so that the piston-cylinder system becomes part of the structure for the purpose of resisting backward forces. The form of undercarriage used on the Messerschmitt Me 108 is shown in Fig. 6. This arrangement might be termed daring in conception and execution, but it is clearly satisfactory, since it has been adopted for their regular production aircraft.. The sideways, force on each wheel appears to be resisted by a couple set up between the pin at the axis of rotation P and the side-thrust between the worm and the teeth in the quadrant, the operation of which
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