DESIGN: AeroVantage ~ Transition Mechanism - Proposed Methods (scale) - 2x4 Underslung Arms [1/8-scale]

• Lengths:
• Center to center of forward and aft motors in cruise positions. = 265mm (10.4") * 8 = (83") The hover gap is therefore 591mm (23.3") * 8 = (186")
• September 24, 2008, The revised one [1674.html] has a movement similar to 1672.html, I.e. the rear arms swing above the wing appear to be the optimum at the present time, in respect to longitudinal stagger and simplicity of mechanism. Center to center of forward and aft motors; The cruise stagger is 268.7mm (84.64") The hover stagger is 585.4mm [184.39"]. The change is 316.7mm [99.75"].
• Rotation of Arm-Major-Forward arm is 157.5º
• The center to center distance between the joints on the Arm-Major-Forward xxmm
• Rotation of Arm-Major-Aft is 157.5º
• The center to center distance between the joints on the Arm-Major-Aft is xxmm
• The recommended blade Axi has a 9" diameter (114.3-mm radius). The current mechanism provides sufficient room for this propeller diameter in the aft and a slightly larger one in the front.

Animation of Transition

• The Arm-Mid-Aft has been lowered so that it does not stick up above the wing.
• The gearing between the Major arms fore and aft is tentatively metric Module 0.5, 20 & 40 tooth, molded bevel gears.

• Disk Area:
• Leishman says, "... the wake of the upper rotor contracts quickly (within 0.25R below the rotor) so it can be considered fully contracted by the time it is ingested by the lower rotor. The ideal wake contraction is 0.707 but in practice it is found closer to 0.8." [radius, not area]
• Since the forward disk has a radius of 159.9mm and an area of 79,955mm², it means that the rear disk must have a radius of 127.6mm radius and an area of 51,171mm².
• Total disk area = (79,955mm² + 51,171mm²) * 2 = 262,252mm² = 2,623 cm² = 0.262 M²
• The ratio of the fore and aft disk areas is 1.56:1.
• Disk Loading:
• Total weight of craft = 1,182g.
• Disk Loading = 1,182 / 2,625 = 0.45g/cm²
• Moments:
• The forward arm distance from the center of the hovering motor to 25% of wing's chord; for large disk = 258mm.
• The rear arm distance from the center of the hovering motor to 25% of wing's chord; for small disk = 342.3mm.
• Forward moment = 799cm² * 2 * 0.45g/cm² * 25.8cm = 18,553cm-g. 24cm arm gives 17,258cm-g. 23.8cm arm gives 17,115cm-g
• Rear moment = 512cm² * 2 * 0.45g/cm² * 34.2cm = 15,759cm-g. 37cm arm gives 17,050cm-g. 37.2cm arm gives 17,142cm-g
• To longitudinally balance the thrust on the blades quarter-chord means that there must be a rearward shifting of the transition mechanism by approximately 3cm.
• Also it will be advantageous to reduce the disk loading (larger diameter rotors -re. Inefficient electric power); as long as the ground clearance on the front PropRotor in cruse configuration is great enough.

• The worm & wormgear, plus the crown and spider gears at the mechanisms must be capable of supplying a very high torque when the mechanism is leaving the hovering position. This is because the thrusts of both fore and aft proprotors are opposing the motion of the transition mechanism.

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