As my user-name suggests, I'm new to KAP, having been doing this for a little less than a year... so my apologies if I've inadvertently replicated anyone else's designs. I'm putting this here to straighten my ideas in my own mind and hopefully to gain a little feedback for further development.
Before I begin proper, I'd like to set a little terminology re the movement of the rig to keep myself organised.
Yaw, pitch, and roll are described as in the above picture - taken from http://www.qfom.com.au/principlesOfFlt.html
The nose of the aeroplane is 0', the pilot's right-hand side or 3-o-clock = 90', the rear of the plane or pilot's 6-o-clock = 180', and the pilot's left hand side or 9-o-clock = 270'.
The kite flies at 0', the kite flier is at 180'.
The aeroplane is the pendulum, and the kite-line angle is ignored in the above.
I've been thinking about pendulum stability for a while, now, and have made a first prototype of a few ideas.
I fly in very light and generally laminar winds at this time of year, and need a lightweight rig. In the picture below, I've used bicycle spokes, bamboo, and copper pipe as those are the materials I have easy access to; kite supplies are strictly mail-order only... mail-order actual delivery
being a singularly exasperating experience in my part of the world.
An overview - right-click and save for a larger image.
1a is a solid-soldered, square cross made from copper pipe - nothing can move at this part.
Both A-C and B-D are single bicycle spokes @ 30cm long and 2.25mm dia and both pass through 1a, crossing at their central points.
Both A-C and B-D are soldered at all exits from 1a.
A to C is the kite-line hanger. Re the terminology introduction, A is 0' or the "kite end", and C is 180' or the "kite flier's end".
1b is the same as 1a
At points B and D, two further 30cm bike spokes are connected with 2" of coiled wire spring... 1" pushed onto each spoke. The outermost end of each spring-attached spoke is bent at 1" from its end and soldered into 1b.
E-F is a single 30cm spoke, soldered in place exactly as A-C, B-D.
At points E and F, two further 30cm spokes are attached with sections of spring as in points B and D. These spokes pass down to G, where they are held in place under bending tension by being passed through a small section of drilled bamboo.
A-C, E-F, and the bamboo at G are all parallel and vertically aligned.
Ok, now that's out of the way.
B-D is allowed to rotate in pitch ('plane nose = up and down) by the springs, which allows A-C to change angle through around 160'. As A-C is the kite-line hanger, this means the kite line angle movement does not affect the horizontal alignment of E-F or G.
A slight torque is passed into the joints of the 1b cross as the springs turn their attached "downspokes".Yaw
On a taut line, yaw is all but eliminated as the B-D spoke cannot move from its square alignment. Neither E-F, nor G can easily be moved from parallel alignment with A-C provided that within the spring joints, the ends of the spokes are pushed to within 2 spring coils of each other.Roll
The pendulum swinging in roll (the airplane wings dipping or rising) is taken care of by the spring connectors at points E and F, so G can swing under points B and D - correcting for roll. A 2m pendulum is attached below G with a small weight at its bottom end. The camera is placed immediately below G at the top of the pendulum.Pitch
No progress as yet. The whole pendulum can swing in either direction from the kite to the flier. With a camera pointing to 0' or the nose of the plane, this would give a horizon moving up and down within a photo frame.
A down - aeroplane diving
A up - aeroplane climbing
Roll into point B down - aeroplane left wing down
I'll add further pictures of the pendulum and camera tomorrow.