i was watching the history of lumbering last night on the history channel.
they showed radio controlled cable releases on the drag lines. these hold up
entire (large) trees in midair, so would be exactly what you're looking for.
you don't say where you are (and the homepage of your school doesn't have an
address on it), but if you're anywhere near where they do logging, perhaps
your crane operator can find one of these for a day.

regards,
charlie
http://glassartists.org/chaniarts

"TJH" wrote in message
ups.com...
OK, perhaps this might sound strange, but I'd like to drop a car from a
crane.

I'm thinking about doing a project for a high school senior class to
show the violence of an auto crash (educational for prom week) at
roughly 30-45mph. In order to do this, I'd hoist an auto by a crane up
say 40 - 50 feet, and then drop it to the ground. But, to do this, I
need some type of quick release mechanism, because the crane owner
isn't going to risk damaging his equipment by free-falling the cable.

I've thought about using heavy duty strap webbing with a quick release
buckles, but I'm not sure if they would support the weight. The release
has another problem - how do I do it from the ground? Ideally, I would
have some sort of remote controlled release, but wireless? Wired?
Mechanical? Cheap and easy is the challenge as well.

If any have any suggestions, I'd love to hear them.

Thanks in advance,

TJ Hanlon
SRO, Pawling Schools