Item 1240

DESIGN: Dragonfly ~ Control - Flight - Spider - Torque Tube & Joint

Drawing:

xxx

Note:

Universal Joint in Control Linkage:/P

A knuckle joint will not do because of the angular motion in two planes. The Miniature Catalog has desired sizes. Don't know about the quality but the maximum torques looks good. The following is information on the difference in angular position caused by a universal joint; and this looks like an advantage.

 

β

Flap angle

Assumption that maximum flap is ± 10º

 

α1

Control pitch angle

Assumption that maximum pitch is ± 15º

 

α2

Blade pitch angle

 

α2 = arc tan (tan(α1) / cos(β)) = arc tan (tan(15) / cos(10)) = arc tan (0.2720 =15.22Ί

I believe that the above means that the blade's pitch will be 0.22º greater than the control's pitch at the azimuth of maximum flap. This is based on the arm of the joints 'X', which is attached to the control, being horizontal and the arm, which is attached to the blade, being vertical. Therefore, I assume that if the joint was installed with the rotation be 90º different from the forgoing, then the 0.22º of pitch will be pulled from the blade's pitch. It appears that this will have the same effect as a small δ3 angle of 1.25º.

For supporting information on the above see; OTHER: Mechanical - General ~ Universal Joint Kinematics

Universal Joint:

Could one or both yokes be replaced by blade grip and or torque tube? This might allow for a larger 'X' and stronger joint at less weight. Consider buying a larger joint and just using the 'X' and bearings. The yoke will serve as a template.

Consider which radial position of the joint's 'X' arms is best for the operation of the pitch change. 

Torque Tube:

xx.

Spline: Put here?

Fits: Sliding fit.

Tooth Form System (Pressure Angle): 30 degree - Used when members are allowed to slide.

 

Information on regular splines: OTHER: Mechanical - Spline

Information on ball splines:

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Last Revised: August 29, 2003