TJH wrote:

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.

Google "three ring release", which is a quick-release system designed to
reliably work under load and is commonly used on parachute harnesses. You
might have to add an additional ring to release a car under load, but
should work fine--big problem is that you'd have to stitch together some
heavy webbing--if you've got access to an industrial sewing machine it
shouldn't be any trouble.

Another way would be to use a pyrotechnic cutter--they're purpose made for
this kind of thing.

Either could be released with a long lanyard--the three ring release is a
bit more complicated to make but doesn't involve any pyros, which in a
school environment I suspect could be a problem.

If the Pawling Schools are the ones in Connecticut you might want to give
Pioneer Aerospace in South Windsor a call--I wouldn't be surprised if they
had an out of date cutter or two awaiting disposal that they might be
willing to contribute to the project, but they might have to send someone
to supervise rather than turning you loose with a pyro with enough power to
seriously injure somebody. OTOH, they might not want to get involved--I
haven't been in there in 20 years and I don't know what they're like now.




Thanks in advance,

TJ Hanlon
SRO, Pawling Schools

--
--John
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(was jclarke at eye bee em dot net)