A086

DESIGN: Dragonfly ~ Control - Flight

Phase Lag & Spider? Arm Azimuth: Note: not now using this type of delta-3

Pitch-Flap Coupling (delta3):

It appears that the universal joint inserts a small amount of delta3 into the control. This should be an advantage. See Method C in OTHER: Flight Dynamics - General - Pitch-Flap Coupling (delta-3):

Pitch Angles:

The following is from the SynchroLite and will be used here (at least for now)

Collective +17º to - 3º = total of 20º of pitch change at the pitch horn.
Longitudinal cyclic +13º to - 9º = total of 22º of pitch change at the pitch horn.
Lateral cyclic +8º to -8º = total of 16º of pitch change at the pitch horn.

Pitch Angle Considerations:

"It is also observed that a flap frequency above 1/rev significantly reduces the tilt required for a given center-of-gravity offset and hence reduces the cyclic control travel." ~ [Source ~ HT p.248]
Sikorsky XH-59A ABC Control System Data and its Change ~ Explanation of its Change

Notes re Pitch Angles:

Typically each individual blade requires a pitch range of more than 30º. [Source ~ HFD p.17]

The Robinson R-22 has a total longitudinal cyclic movement of 20º and a collective movement of 13º.

The MBB BO 105 CB has a total longitudinal cyclic movement of 17º and a collective movement of 17º.

Potential Improvement:

Bring the rotors (i.e. the swashplates) closer together so that the control rods from the mixer-box to the swashplates are more perpendicular to the plane of the swashplate.

Slightly reduce the arm lengths, which connect to the control rod, in the mixer-box and in the swashplate. This will give the swashplate a small diameter and will give more clearance in the tube.

Consider putting some Hub Spring in the rotors. A second possible advantage of incorporating some form of hub spring may be that of negating the need for droop stops.

Vibration Isolation:

See: DESIGN: SynchroLite ~ Control - Flight ~ Vibration Isolation

Considerations for the Future:

Consider making the rotor and flight-controls in a manner whereby they may be modified to be more like the UniCopter in the future.

It might be possible to eventually have;

DESIGN: UniCopter - Rotor - Disk - Independent Root & Tip Control by locating a small yoke universal joint inside a larger yoke universal joint, plus one torque tube within another.

Greater strength and rigidity in the blades and rotor hub etc.

Etc.

For future flight control or safety device etc.

It looks like there is a 'passageway' from the base of the control stick all the way to the three blades; as long as the collective is not in the way. Control for tip or root drag brake, plus whistle on tip brake, is a consideration.

For future flight control or safety device etc.

Hydraulic .

Consider using conventional single rod cylinders which all have the same bore and rod diameter. There would be two distinct hydraulic plumbing systems. One system interconnects the portion of the cylinders without the rod and the other system interconnects the portion of the cylinder with the rod. I.e. one cylinder but two oil lines and fittings etc.

This will work in with a hydraulic governor.

Electric:

Consider an all electric flight control system. The actuators, such as stepper motors, could be located in the yokes and connected directly to the spline of the grips.

Stepper Motor Web pages:

http://www.eio.com/stepindx.htm STEPPER MOTOR Information and Technical Forum

Control of Stepping Motors

This will work in with an electric governor.

Same Page ~ Different Craft: ~ SynchroLite ~ UniCopter

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Last Revised: December 25, 2004