Shut-Off Ideas

Please note that now there are commercially available mechanical shutoffs that are easy to install, work reliably and are relatively cheap (e.g. from Viko). The ideas and designs mentioned below are now of historical interest only.

Links

• http://www.e-shutoff.com/ - Mike Wilcox's electronic shutoff site

• http://www.f2d.dk/shutoff/shutoff.htm - Henning Forbech's shutoff site

Generic Information

• Henning Forbech's experiments:
  • need a "close" line tension of at least 0.7 kg to be able to handle lines-and-handle fly-away.

Here's Henning's important figure reproduced here.

Line-tension spring idea (Pete Athans)

Tried some spring experiments:

• spring specs (Aussie Springs, Mitre10):
  • length 70mm (50mm of coils+20mm end loops)
  • wire diam 0.9mm
  • max deflection 154.4mm
  • max safe load 1.6 kg
• tests
  • with latex (~2mm ID): deflection opens 61-80 mm (first distance just leaks, second is no restriction) - 1 kg to open
  • with green fuel tubing (Hobbyrama): opens 52-62 mm - 0.7 kg to open
• ideas
  • need to figure out how much spring extension to use
    • we don't want the spring to bend the leadouts back over themselves
    • so we need just a small spring extension
  • make perhaps 4 small springs out of the purchased one, each capable of a small extension, but would only pull back 40 mm or so (see the (first?) smaller spring version below (without a spring hook!)

Swing-arm shut-off

These are not popular but are relatively simple to install (no line strings etc). It would be nice to remove what seems to be their biggest problem - damage on collisions with another plane or the ground, mostly bending of the swing-arm.

Ideas:

• put the swing-arm pointing forwards, so that forward g-force from a collision will simply try vainly to straighten the arm.
• constrain the movement of the arm (close to its free end) to be just enough to shut off the fuel, but not enough to let the weight pull forward and bend the arm.