Hitching a ride on the kite line.

I have been using a pendulum suspension for a good while now and, although it’s not the lightest method, it has some advantages over the Picavet.

  • robust
  • tangle free
  • no knots to unravel or line to fray
  • less cross line swing
  • cheap: a set of 4 KDH pulley blocks for a smooth Picavet are eye wateringly dear.

I got an email from a Kapper who has made one and he asked how to hitch it to the line. I started to try and describe how to do this this in words and gave up. What’s needed here are pictures: _DSC0014 _MG_2911 _MG_2912 The pivot bar can fly either way up, I prefer it pointing down as I believe the upwind section of line from the pivot point vibrates less than the down wind section (it’s longer). The most important thing is to make sure the line is not in contact with the bar edge on its exit path. Slack line diagram-1 Note that all the nuts on the pivot bar are ‘nyloc’, all its edges have been rubbed smooth. The top bar of the pendulum is M6 threaded to accept the 2 nuts fixing it to the angle plate. It took me a while to get these shots as I find rig launch and recovery are the moments I take my eye off the kite so I waited till I had a good steady flow and was happy the kite was fixed in the sky rather than buffeted about as it has been of late. A  good exposition on pendulum suspension by Christian Becot is here.

As Brooks would say:

Chin UP!

B

About billboyheritagesurvey

Heritage worker
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2 Responses to Hitching a ride on the kite line.

  1. Tom Benedict says:

    Oh good! I get to pick your brains on something.

    I’m digging back through my notes on the damped pendulum I wanted to build a while back. One question I had was which end to place the pivot on. My wife and I went back and forth over the physics, and when I last touched my notes I’d decided to make it so I could place the pivot anywhere along the bar. (I also made a note that this was heavy, awkward, and could be answered in a few test flights.)

    So you place yours on the downwind / upslope end of the bar? I’d wondered which end of the line experienced more vibrations. It’s tough to tell since I haven’t actually flown a pendulum yet.

    Thanks for writing this article. I’m going through your set of three on building contour maps right now, too. I really appreciated your section on number of images versus number of pixels, and how each affects the quality of the resulting DEM. That’s something that bothered me about Photosynth back when I was playing with it. They down-resed (whatever the past-tense of down-res is) to 5MP, regardless of what you uploaded. GRRR! No matter how many images I threw at the problem, the resulting point clouds were always noisy. Now I know why!

    • Hi Tom,
      The pendulum I used is the fruit of Christian’s work. He has done the work and I have looted from it the bits I need. I believe the suspension beam has almost no effect on the stability except as a damper against twist in the horizontal axis. The really big discovery Christian made was the effect of plastic tubing in killing transmitted vibration,that and slack line are the 2 key aspects to this. In time I am going to reduce the rod diameters to save weight but there is no rush as this pattern works well. I have anxieties about line abrasion still and would like to engineer a foolproof hitch post to stop that- the line tension on the toggle can be huge.

      The down sampling issue is not easy to solve, I have pretty near killed my PC processing this tiny patch of Cambridgeshire so if I add any more surface to the model something will have to give!

      B

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