DESIGN: AeroVantage - Transition Mechanism - Proposed Methods - Underslung Arms

• This was the simplest and the most aerodynamically clean; until 1655.html, and later ones.

• The worm & wormgear must be capable of supplying a very high torque when the mechanism is nearing the hovering position. This is because the thrusts of both fore and aft proprotors are opposing the motion of the transition mechanism when nearing the hover position. Consider using springs to offset some of the hovering thrust moments.
• The loading via the gears is to be transmitted (distributed) via 2, 3 or 4 spider gears.
• Perhaps making the rotation to hover about 5º less will reduce the required torque while not having any appreciable effect on the for-aft gap between rotors.
• Perhaps adding some 'spring' to assist for the firsts approximately 30º of rotation from hover to cruise.
• How to have the frame strong enough to resist bending. The weight can be kept low by the use of composite construction.

• Notes:
• The Major Arms are the red arms on the drawing.
• The Minor Arms are the purple arms on the drawing.
• The Minor Arms are connected by a tube at the top (and the bottom if possible) so that they rotate together about a common shaft and thereby give the mechanism greater rigidity.
• Forearms are the blue arms on the drawing.
• Changes to be made:
• Increasing the lengths of the Upper-arms will increase the stagger between the proprotors during hover and decrease the stagger between them during cruise.
• The Wrist-rod should probably be connected to the Secondary Upper-arms instead of the Primary Upper-arms, for simplicity.
• The primary hinge at the wrist (motor) should probably be moved up the motor's axis, closer to the proprotor, for improved stagger and reduced greater gap between the rear proprotor and the ground.

• Linkage: 6 bar, 1 degree of freedom (rotation). Reference; Watt-1, Linkage.
• The center-to-center distance between the joints on the ends of the main arms determines the longitudinal (transnational) movement of their respective PropRotor.
• The center-to-center distance between the joints on the ends of the minor arms is just enough to clear the motors.
• The longitudinal location of the X-shaft determines the longitudinal position of both of the fore and aft PropRotors in both modes.
• The center-to-center distance between the joints on the ends of the mid arms is the same as that of their respective main arms

• The rotation at the shoulder WAS 180 - (2 * 7.64) = 164.72º. IS 172.5051º.
• Operation; Option A: Each upper arm has a worm at the shoulder and at the elbow, which are driven by a common shaft and motor. There is a partial wheel at the elbow of the lower arm and at the shoulder of the cross-tube.
• Operation; Option A: The rotation at the shoulder is transferred to the elbow a shaft in the upper arm and miter gears at each end of the shaft. The port and the starboard forward units would be mechanically tied together by a cross-shaft. The port and the starboard aft units would be mechanically tied together by a cross-shaft. The, if desired, the fore and aft assemblies could be mechanically linked by gears. The rotation at the shoulders will cause an equal rotation at the elbows.
• A thought: The aft segment of the wing that is being considered for rotation with the aft Proprotor could be sized so that the thrusts of the PropRotors does not cause an undesired pitching of the craft during transition.
• Also, A smaller version of this might be considered for the forward PropRotor.
• The forward Proprotor will create a greater moment on the X-shafts than the aft PropRotor will. This is because the forward major arm is longer that the aft one.
• Consider pivoting guides for the Wrist Rods. The am length ............????

• Primary Dimensions: The Ctr to Ctr distance between the pivot points on the Major arms is just about the longitudinal movement of that arms PropRotor. It is not quite because the arms do not rotate a full 180º

• Motor Rotation:
• The rotation of the main arms is 180 - 25 = 155º.
• The rotation of the motors is 90º
• Therefore the ratio of the arm lengths on ends of the Wrist rods are 155:90 = 1.7222:1. I suspect. Perhaps not ~ see drawing

• Drive of Transition Mechanisms:
• Consider miter gears at both ends (one end?) of the X-shaft. The spiders are locked to the transition frame. Large gears are attached to the forward X-shaft and the aft X-shaft. A hollow shaft worm and wheel gearmotor rotates one of the X-shafts.

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