145,012. Hewitt, P. C. June 14, 1919, [Convention date]. Helicoptcrs; propelling; steering, balancing and regulating altitude.-Relates to the construction and mounting of the lifting propellers for flying machines of the helicopter type. Upper and lower propellers 1, 2 are mounted on concentric vertical shafts 3, 4, which are driven in opposite directions by motors 8, 9 through bevel gearing 10, 11, 12, 14. Each of the gear wheels 12, 14 is thus subjected to a turning couple, and thrust on the bearings is avoided. Each of the wheels 12, 14 is formed with a rigid ring portion 15, Fig. 3, supported by a flexible plate 16 and engaging the pinions 10, 11. The gears are maintained coaxial by a ball bearing 18 between members 19, 20. The gears are maintained in engagement by rollers 24 supported from the frame of the machine by straps 25. Each propeller is provided with two radial arms 26 carrying blades 27. Each arm 26 is mounted for movement around its longitudinal axis to vary the pitch of the blades, and is provided at its inner end with a circular flange 28, Fig. 13, secured by bolts 29 to a vertical flange 30 projecting from a flange on the propeller shaft. The bolt-holes in the flanges 28 are elongated so that the arms 26 may be fixed at any desired pitch. Each arm 26 extends the full length of the blade 27, which is held in position by cross-braces 37, Fig. 2, and a cross-arm 38, which is connected by guy wires 39, 40 with the arm 26 at a point between the axis and the arm 38. Similar wires 41, 42 are connected at a point near the outer end of the blade. Tension wires 43, 44 are secured to rigid arms 45, 46 on the propeller shaft and also to the arms 26 to transmit, the drive. Other tension wires 47, 50 are also provided. The propeller 1 is braced against vertical strains by tension wires 52, 53, 54, 55, 56, 57, 58, 59, Fig. 1, and similar bracing is provided for the propeller 2. The arms 45, 46 are channel-shaped, as shown in Fig. 3, to secure rigidity, and are secured to flanges 34 and 70 on the shafts 4, 3. Channel brackets 71, 72 are also fixed to the flanges 70 and 34 respectively, and the side flanges are secured together by gusset plates 73. The arms 45, 46 and their connexions are shown in detail in Figs. 4 and 5. The wires 44, 47 and 43, 50 are connected to the arms 46, 45 respectively by nuts 80 bearing against loops 81 on the outer ends of the arms. Wires 86, 87 are attached to the propeller shaft and to the shanks 83 of the loops 81, inclined surfaces being provided against which the nuts are seated. The wires 52, 53, 54, 55, 86, figs. 4 and 5, are provided with nuts 91 bearing on bridge members 92, which are movable longitudinally on the arms 93, 94 of staples 95. The staples are threaded through openings in a circular flange 96, and the wires may be tightened by nuts 97, 98 without any twisting of the wire. The method of securing the wires to the arms 26 is shown in Fig. 7. A flat plate 103 is provided with lugs 104, 105 at right-angles to its surface, the width across the lugs and across the plate being each equal to the internal diameter of the hollow arm 26. The cross-member thus formed is inserted longitudinally into the arm 26 and anchored in position by pins passing through the arm and through openings 106 in the plate 103. The wires to be secured are threaded into openings 107, 108. Figs. 10 and 11 show a device fur securing four horizontal and two inclined wires to one of the arms 26. The plate 110 is provided with lugs 111, 112 in its own plane and lugs 113, 114 at right-angles, all being thicker than the plate 110. The wires to be secured are threaded into openings such as 115, 117, 118, 121, 122, the body portion being cut away as at 123, 124 for that purpose. The lower frame, Fig. 1, is composed of tubular arms 125, 126 connected to the tube 5. The shafts 3, 4 pass through the bearing 5. The shaft 3 is formed of two parts 130, 131, Fig. 3, the upper part of the shaft being increased in thickness at a point adjacent to the flanges 100, 101, i,e. between the upper and lower propellers, to provide for bending strains during lateral night. Ball-bearings 133, 134, 135 maintain the shafts 3, 4 in coaxial position, and bearings are also provided to take the weight of the propellers. The shaft 4 carries a sleeve 141 on which is mounted in order a collar 142, sleeve 143, collar 144, sleeve 145, and hub 17 of the wheel 12. A thrust bearing 149 is arranged between the collars 142, 144, and a bearing 152 between the collar 144 and hub 17. A casing 153 encloses the bearings. These bearings provide for the upward thrust of the propeller 2 during rotation, and for its weight when stationary. bimilar bearings are provided for the shaft 3. Each propeller arm 26 carries a number of cross-braces, arranged more closely towards the outer end of the blade, and upper and lower plates 171, 172, Fig. 16, are riveted to them. Each cross-bar and the side-plates are constructed of aluminium, and the cross-bars are provided with top and bottom flanges 174, 175 for the attachment. of the side plates, and with circular flanges for attachment to the arm 26. Wedge-shaped, blocks 177, 178 are arranged between the flanges 174 and the tube 26. The two ends of the cross-braces are provided with longitudinal, strips 181, 182 to connect the flanges together. The propeller blade is supported on the tube 26 so that its support is forward of the centre of pressure and the blade is pulled and not pushed by the support. The blade may be sufficiently flexible to permit of an automatic variation of the pitch by the air pressure. The machine is turned about, the axis of the shafts 3 and 4 by planes 200, 201, Fig. 1, which may be tilted about a horizontal axis in opposite directions. The downdraught from the propellers then produces a couple tending to rotate the machine. The planes 200, 201 may also be rotatable, about vertical axes 200<1>, 201<1> so that they may be used as rudders. If the machine is required to be tilted to produce lateral motion, one of the planes 200, 201 is turned into the horizontal, and the machine may be kept in tilted position by planes 202, 203, which may be inclined to the horizontal.