Rope Cutting Mechanisms
I know two rope cutting methods. In none of them a rope
is actually cut. In the first one a rope is melted by
a soldering iron. In the second one only ice melts.
Soldering Iron with Electronic Timer Device.
This method is easy to use, and reasonably reliable. The idea
is simple: A soldering iron gets hot enough to melt
through a nylon rope. Tie a nylon rope around the soldering
iron with a simple knot, as is shown on the drawing below.
The soldering iron can be connected to
an electronic timer. Approximately 2 minutes after the
soldering iron is switched on, the rope melts, and it will give way.
As far as I know soldering irons are not capable of starting
a fire. I have tried two irons on various materials, namely
plastic (PET), alcohol, wood, wax. None of these ignited.
The only thing that I could ignite was the head of a match.
Make sure that the rope is made from nylon, because otherwise
it may not melt. Think about where the soldering
iron goes after the rope has melted. Make sure it won't
touch anything made out of plastic, your carpet, its
own wire. Make sure that it cannot touch you!
Put a board under the soldering iron.
Don't use the tip, since the tip is usually not very
firmly connected to the frame.
The frame usually does not get hot enough at all places.
Usually it gets only hot near the end.
There must be a fairly high
force on the rope to make sure that the knot is pulled
tight against the frame.
This makes the method
inappropriate as key release method. Test the construction
many times!
Here is a drawing of the construction:
Icecubes with Force Divider.
If you impose a high force on a icecube it will break.
However it is possible to divide the force as is shown
in the drawing. This makes it possible to construct
a rope cutting mechanism based on ice. I have used the
construction for suspension, so it is capable of supporting
pretty high forces. Test it in advance with something heavy.
Don't attempt to save on the metal rings. If you put more
than one loop
through the same ring, the construction becomes
extremely unreliable. In fact it fails approximately
half of the times. Here is a drawing in which I attempt
to explain what goes wrong:
Pictures of Soldering Iron and Icecubes with force divider
soldering iron and icecube method should always be combined:
Detail of icecube with force divider:
