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Aviation History
1944
1944 - 0966.PDF
5o2 FLIGHT MAY IITH- IC)44 BRITISH body was an Elektron cast ing and carried the spiral bevel gears which were mounted on an axle run ning in large-diameter ball bearings and passing the torque through a ratchet- type freewheel to the upper portion of the axle and blade articulation. In the pictures of the rotor hub may ibe seen the flapping and drag articu lation of the three blades, and the link connections to the centrally placed fric tion damper. The blade- root fitting vernier adjust ments were supported on radial bearings and heavy- duty thrust races to meet the centrifugal loads. The blades were constrained in torsion by a special form of constant-velocity joint situated on the com mon centre of the drag and flapping hinges. This special form ot joint was necessary to allow of drag and flapping displacement without affecting the pitch change. Pitch Articulation Inwardly projecting arms or cranks (see photographs), splined to extensions of the pitch articulation, carried spherical joints which, in turn, were positioned on the con necting-rods. Reciprocation of the connecting-rods caused the blades to turn about the torsional hinges. Movement of the three connecting-rods in the same direction caused the blades to take on or discard pitch, such as might be required for rolling control. Differential movement of the connecting-rods produced harmonic variation of pitch for control about the pitching axis, or inclination of the lift vectors for translational speed, forward or backward. Application of the rolling control could be used to cause the machine to fly in either lateral direction. The connect ing-rods carried, at their lower ends, a form of spherical joint similar to that employed at the top link connection and were coupled to a yoke which, in turn, was located The tapered and shouldered blade hubs. Note the metal leading edge and its attachment. Jet-propelled rotor blades have been patented by Mr. C. G. Pullin for Weir helicopters. On the left are three types of jet nozzle. The upper right-hand drawing shows the turbine-compressor ^^ power unit in the machine, and details are clearer in the enlarged view, in which A is the air inlet ; B, the combustion chamber ; C, effluent duct; D, central member ; E, compressor rotor ; F, guide vanes ; G, exit vanes ; H, fuel nozzles ; J, igniter plugs ; K, turbine entry vanes ; and L, turbine rotor. on a swashplate member by ball bearings and free to rotate thereon and to rock about a bell-crank pin. The control piston supported the bell-crank and a yoke which, under the influence of a lateral control sprocket and a threaded member coupled thereto, effected a rise and fall of the.piston, thus changing the pitch angle of all blades simultaneously. Harmonic pitch change was produced by turning another sprocket (pitch axis or fore- and-aft control) which allowed the inner threaded member to displace in an axial sense the lower bell-crank pin, thus forcing the swashplate member to rock about the pin. This displaced the connecting-rods differentially from the hori zontal datum, thus introducing harmonic pitch variation around the rotor disc. The magnitude of the pitch oscil lation thus depended on the amount of applied control.*' Both lateral and fore-and-aft controls could, of course, be applied at the same time, and also differential tilt of the lift vector for control about the yawing axis. A short, universally jointed shaft and coupling took its drive from a universal joint and, being secured in the yoke member, located the swashplate member in correct phase relationship and, at the same time, permitted of torque-free functioning of the connecting-rods and links. An hydraulically operated brake was incorporated for parking and for slowing-down the rotor after landing. Change-over from helicopter operation to autorotation was accomplished by closing the engine throttle. A pre-deter- mined reduction of rotor speed caused the blades to change pitch through the medium of a hydraulic relay similar to the well-known constant-speed unit. An additional torque-balanced unit, working through the medium of the same relay, eliminated the possibility of overturning in the event of the failure of either transmission shaft or drive component. It is very much to be hoped that this pioneering work on helicopters, which has now been resumed, will not go unrewarded, and that sufficient official support will be given to bring the work to fruition. Lord Weir and his brother. Air Commodore J. G. Weir, have spent vast sums of money on autogiros and helicopters, and only their Scots determination could have faced for so many years the number of set-backs with which the path of the pioneer is ever beset. If Great Britain is found to be well in the forefront of helicopter development, and we have every hope +hat this will be so, the credit will be almost entirely due to the faith—and the long purse strings—of the brothers Weir, and to the technical ability of Mr. C. G. Pullin.
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