GB145011A - Improvements in and relating to flying machines - Google Patents

Abstract

145,011. Hewitt, P. C. June 14, 1919, [Convention date]. Helicopters; propelling; steering, balancing, and regulating altitude.- Relates to lifting propellers for flying machines of the helicopter type. An upper propeller 1 is mounted on a vertical shaft 3 which passes through a tubular shaft 4 carrying a lower propeller 2. The shaft 4 extends through a stationary tubular bearing 5 forming part of the frame 6 of the machine. The diameter of the propeller should be between T/H.P. Î #T/17 and 0.7 T/H.P. Î #T/17 where T is the total lift of the propellers in pounds, and H.P. represents the horse-power. The shafts 3 and 4 are driven in opposite directions by motors 8 and 9 arranged with their driving shafts in the longitudinal axis of the car 7, and provided with bevel pinions 10, 11 meshing with larger pinions 12, 14 secured to the shafts 4, 3. Each of the shafts 3 and 4 its thus driven by a couple, and lateral thrust is eliminated. The propeller blades 27 are long and narrow, and are supported on internal radial arms 26 in such a way that the line of support is forward of the centre of pressure upon the blade. An automatic adjustment of the pitch angle of the blades within certain limits is thus obtained, the support of the blade being somewhat elastic. The inner end of the blade terminates at a point between one-fifth and twofifths of the radius of the propeller from its axis, and the ratio of length to breadth of the blade is preferably not less than 5 : 1. The blade area for all four blades is about 6 per cent of the propeller disk area, but for slow speeds it may be 9 per cent. The pitch angle of the blades is about 6 degrees to 24 degrees to the horizontal, but for fast machines the pitch may decrease towards the centre of the propeller. The actual pitch angle is several degrees greater than the most efficient pitch angle so that when the machine is passing horizontally through the air the efficient angle will be obtained when it is tilted from the horizontal. The propeller blades are preferably constructed of aluminium, and their speed is not greater than one-eighth of the engine speed. To turn the machine about, its vertical axis, planes 30, 31 are attached to the extremities of the arms 32, 33 below the propeller blades, and may be tilted in opposite directions from the vertical. These planes may be used to correct any rotation due to unequal action of the propellers. The planes may also be rotatable about vertical axes 30<1> and 31<1> to turn the machine when it is moving horizontally. To produce lateral motion, only the plane 31 is moved to horizontal position so that the downward air current forces this plane downward and tilts the machine. Planes 34 and 35 are provided to maintain the machine tilted. These planes are not subject to the air current from the propeller, so that they are only acted upon by the current due to translational motion when tilted about axes transverse to the arms 32, 33.