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

Very heavy duty quick-releases are available from theatrical rental outfits.
They're frequently used in special effects. There was even a close-up and
description of one on "Mythbusters", where they did exactly what you plan to
do, complete with Buster the myth-busting crash test dummy.

DON'T cobble up something yourself, unless you have the liability insurance
to cover you. It isn't worth it for the price of a rental.

LLoyd

"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.

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.

A marine snap shackle might work:

http://shop.torresen.com/ships_store/?p=categorydetails1&defaultbrand=Ships+Store&defau ltstore=Ships+Store&sectionid=5111

Another possibility, if you can persuade the crane owner to allow it,
is to fit a "headache ball" to the cable about 20-30 ft above the car.
Probably the headache ball would be part of a hook, and you'd have to
add a second length of cable between the hook and the car. The idea is
that you free fall the cable, but that the headache ball keeps the
cable taut when the car hits the ground. The crane operator then needs
to stop the cable before the headache ball hits the ground. This is a
fairly common system and seems to work okay if the crane operator knows
what he's doing.

Chris

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

A magnetic crane like the ones used at scrapyards would work.
Cut the current and the car will drop.

But for what you're trying to accomplish, why not do it like
all the other prom night demonstrations? Get a car that was
involved in a DUI from the local junkyard. If it still has
the beer cans inside, it's that much more realistic.

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.

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
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)

In article . com,
"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.

A standard bomb release would be perfect. IIRC, in WW2 the japs
strapped the bombs to the plane and used a cutter to release. A heavy
strap (seat belt?) and a paramedic seat belt cutter should work.

--
Free men own guns, slaves don't
www.geocities.com/CapitolHill/5357/

Make a pair of "S" shaped hooks by torch cutting from heavy steel plate.
Attach these together near the middle with a heavy bolt, so they form a
figure "8." Hang the car by cable from this figure "8". As the crane lifts
the car the figure 8 will reach the top pulley, and open. How? You design
it that way.

On Thu, 26 Jan 2006 22:02:20 GMT, Nick Hull
wrote:

In article . com,
"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.

A standard bomb release would be perfect. IIRC, in WW2 the japs
strapped the bombs to the plane and used a cutter to release. A heavy
strap (seat belt?) and a paramedic seat belt cutter should work.

Dad made one by cutting a piece of 1" plate, drilling a hole for a big
anchor shackle, then cutting a notch which held another anchor
shackle. He welded a 3' stick of 1" round to the top to one side of
the hole. In practice, he hooked onto the captured shackle with the
winch truck, and hooked the slot shackle to a chain around a levee
roller, a concrete spool weighing about 2 tons. A rope was tied to
the 3' release handle. He winched to roller in the air, backed over a
junk car, and then pulled the rope from a safe distance. It dropped
the roller just fine, but the junker wrapped around the roller and we
had to cut it off. The objective had been to crush the old cars.

The release was crude, and probably unsafe, but there were no lawyers
around, and if there were we had access to a backhoe.

Pete Keillor

"Charles Spitzer" wrote in message
...
i was watching the history of lumbering last night on the history channel.

I watched that show too. I found the machine that cut the tree at its base,
picked it up and then de-limbed it, all in one fell swoop, pretty amazing.

Peter

In article ,
"J. Clarke" wrote:


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


A safe pyro cutter could be made from a rope wrapped in common smokeless
gunpowder. Ignition by a common model rocket igniter.

--
Free men own guns, slaves don't
www.geocities.com/CapitolHill/5357/

Nick Hull wrote:

In article ,
"J. Clarke" wrote:


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


A safe pyro cutter could be made from a rope wrapped in common smokeless
gunpowder. Ignition by a common model rocket igniter.

Might take some work to keep the powder in place under strain and get the
charge right to make a reliable cut on webbing heavy enough to trust with a
car, but could be done.

The kind used in parachutes are self-contained and can be mechanically or
electrically triggered. If you hold one in your hand and trigger it you'll
want to let it go _real_ fast (they get hot) but it won't do you any
lasting harm. Put your finger in the ring line passes through, and then
trigger it and you _will_ lose that finger. Some are big enough to take a
small-framed person's arm.

--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)

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.

I've already given a serious response, but quite honestly the country boy in
me wants to hoist it on a piece of rope and get out my target rifle and
peck away at it with .22 long rifle until the rope gives way.

Never be allowed to do that these days though.

--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)

J. Clarke wrote:
TJH wrote:

OK, perhaps this might sound strange, but I'd like to drop a car from a
crane.

Check with anyone in the area that does sling loads with helos....even
the local Guard units.. There are hooks made specifically for this type
task that require quick release capability. Should be able to borrow
one pretty easily.

Craig C.

In article ,
"J. Clarke" wrote:

I've already given a serious response, but quite honestly the country boy in
me wants to hoist it on a piece of rope and get out my target rifle and
peck away at it with .22 long rifle until the rope gives way.

Never be allowed to do that these days though.

With .22 shot it could be arranged to be safe but I'm not sure how many
rounds it would take to wear the rope out.

--
Free men own guns, slaves don't
www.geocities.com/CapitolHill/5357/

As a crane operator I would not want to drop a 3000 to 4000 pound weight
suddenly. When the weight is released suddenly the boom bounces upward.
Whether or not that results in damage to the crane depends on a lot of
variables including capacity of crane, skill of the operator, hydraulic
or lattice boom crane. It would not be considered safe practice.

Nick Hull wrote:

In article ,
"J. Clarke" wrote:

I've already given a serious response, but quite honestly the country boy
in me wants to hoist it on a piece of rope and get out my target rifle
and peck away at it with .22 long rifle until the rope gives way.

Never be allowed to do that these days though.

With .22 shot it could be arranged to be safe but I'm not sure how many
rounds it would take to wear the rope out.

Probably quite a few. 12 gage might be a better bet if there's a reasonable
amount of clear space downrange.

--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)

That's a good point about the boom vibrating when a load is released
suddenly. I've never seen a weight released completely as is being
proposed here, but I have seen the "headache ball" system I mentioned
in use on local demolition sites. I assume this allows the operator to
release the brake gradually, avoiding a dramatic vibration in the boom.
If I remember rightly, it was also the system used with the famous
guillotine for chopping up unwanted B52 bombers. Do a Google search for
"b52 guillotine headache ball" (or something like that) for more
details. There are a few pages out there...

Chris

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.

Thanks in advance,

TJ Hanlon
SRO, Pawling Schools


I believe the device your looking for is called a Pelican Hook. The
release is manual via a second rope. Any decent rigging shop or marina
should be able to rent you one or point you a source for purchase.

Jim Vrzal
Holiday,Fl.

Mawdeeb wrote:

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.

Thanks in advance,

TJ Hanlon
SRO, Pawling Schools


I believe the device your looking for is called a Pelican Hook. The
release is manual via a second rope. Any decent rigging shop or marina
should be able to rent you one or point you a source for purchase.

Not designed to open under load.

--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)

J. Clarke wrote:
Mawdeeb wrote:


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.

Thanks in advance,

TJ Hanlon
SRO, Pawling Schools


I believe the device your looking for is called a Pelican Hook. The
release is manual via a second rope. Any decent rigging shop or marina
should be able to rent you one or point you a source for purchase.


Not designed to open under load.


Incorrect. The Pelican Hook was desined specifically to release a cable
or chain under load in an emergency. The trebu chet users use them to
hold the counter balance weight under tension.

http://www.ripcord.ws/triggers.html is one example.

Jim Vrzal
Holiday,Fl

On Fri, 27 Jan 2006 17:35:56 -0600, Paul G. Shultz wrote:
As a crane operator I would not want to drop a 3000 to 4000 pound weight
suddenly. When the weight is released suddenly the boom bounces upward.
Whether or not that results in damage to the crane depends on a lot of
variables including capacity of crane, skill of the operator, hydraulic
or lattice boom crane. It would not be considered safe practice.

Yeah, about that - before dropping a car, you'll want to check with your
school's and FD's insurance companies. I bet the whole question goes
away pretty quick, to be honest.

We always just bash the cars up pretty good with a backhoe. Seems that
about half our department owns one or has owned one.

Dave Hinz

Mawdeeb wrote:

J. Clarke wrote:
Mawdeeb wrote:


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.

Thanks in advance,

TJ Hanlon
SRO, Pawling Schools


I believe the device your looking for is called a Pelican Hook. The
release is manual via a second rope. Any decent rigging shop or marina
should be able to rent you one or point you a source for purchase.


Not designed to open under load.


Incorrect. The Pelican Hook was desined specifically to release a cable
or chain under load in an emergency. The trebu chet users use them to
hold the counter balance weight under tension.

http://www.ripcord.ws/triggers.html is one example.

Read that page carefully--they recommend their pelican hook for a load of up
to 80 pounds, which one can release with a slip-knot. The discussion is of
supporting a car.

--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)

On Fri, 27 Jan 2006 17:35:56 -0600, "Paul G. Shultz"
wrote:

As a crane operator I would not want to drop a 3000 to 4000 pound weight
suddenly. When the weight is released suddenly the boom bounces upward.
Whether or not that results in damage to the crane depends on a lot of
variables including capacity of crane, skill of the operator, hydraulic
or lattice boom crane. It would not be considered safe practice.

There /are/ quick release couplings that will easily work for that -
for a lead on them contact Jamie Hyneman (sp?) at M5 Engineering
Special Effects in the San Francisco area - AKA 'Mythbusters'. They
used them as the drop latch on the "Elevator Of Doom" episode, among
others.

The only way I (NOT a trained crane operator) can see it being safe
to suddenly release the load like that is if the crane is Massively
Oversized for the lift & drop - like a 100-ton monster that is used
for heavy construction instead of a tower crane, and usually has 200 -
250 feet of boom on it. But for this you take every removable section
out of the mast so there's the anchor end and the 25' stinger end,
period.

And even at that, I'd call P&H or Lorain and ask their engineers.
You break one of those puppies, and the parts are not gonna be cheap.

-- Bruce --

--
Bruce L. Bergman, Woodland Hills (Los Angeles) CA - Desktop
Electrician for Westend Electric - CA726700
5737 Kanan Rd. #359, Agoura CA 91301 (818) 889-9545
Spamtrapped address: Remove the python and the invalid, and use a net.

J. Clarke wrote:
Mawdeeb wrote:


J. Clarke wrote:

Mawdeeb wrote:



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.

Thanks in advance,

TJ Hanlon
SRO, Pawling Schools


I believe the device your looking for is called a Pelican Hook. The
release is manual via a second rope. Any decent rigging shop or marina
should be able to rent you one or point you a source for purchase.


Not designed to open under load.


Incorrect. The Pelican Hook was desined specifically to release a cable
or chain under load in an emergency. The trebu chet users use them to
hold the counter balance weight under tension.

http://www.ripcord.ws/triggers.html is one example.


Read that page carefully--they recommend their pelican hook for a load of up
to 80 pounds, which one can release with a slip-knot. The discussion is of
supporting a car.


That page was offered as an example that the hooks will release under
tension. Now its just a matter of scale. Larger load, larger hook.

A short review of a google search will revel pelican hooks for chain
with capacities of 50000 lbs are commercially available. P Hooks used
with 1/2 inch steel cable start at 4000 lbs which should be sufficent
for the original posters needs.

As the other posters have indicated, the real concern will be the crane
operators skill to control the rig when the load lets loose.

By the way, your manual is ready to send. Need a address to send to.


Jim Vrzal
Holiday, Fl.

Mawdeeb wrote:

J. Clarke wrote:
Mawdeeb wrote:


J. Clarke wrote:

Mawdeeb wrote:



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.

Thanks in advance,

TJ Hanlon
SRO, Pawling Schools


I believe the device your looking for is called a Pelican Hook. The
release is manual via a second rope. Any decent rigging shop or marina
should be able to rent you one or point you a source for purchase.


Not designed to open under load.


Incorrect. The Pelican Hook was desined specifically to release a cable
or chain under load in an emergency. The trebu chet users use them to
hold the counter balance weight under tension.

http://www.ripcord.ws/triggers.html is one example.


Read that page carefully--they recommend their pelican hook for a load of
up
to 80 pounds, which one can release with a slip-knot. The discussion is
of supporting a car.


That page was offered as an example that the hooks will release under
tension. Now its just a matter of scale. Larger load, larger hook.

A short review of a google search will revel pelican hooks for chain
with capacities of 50000 lbs are commercially available. P Hooks used
with 1/2 inch steel cable start at 4000 lbs which should be sufficent
for the original posters needs.

Which alters the point how? Or perhaps the point that escapes you is that a
pelican hook, no matter how large, was not designed as a device to suddenly
release a heavy load by pulling on a lanyard. Typical use for the large
ones you mention is to restrain anchor chains on large ships and thus free
the windlass for other uses--they are not intended to release easily under
load and in fact doing so would be a disadvantage in that use. To release
the pelican hook the load on the chain is usually taken up by the windlass.

The little one works on toy trebuchets only because it is not subject to
much load. Note that even their larger model that is based on the pelican
hook concept is modified considerably to remove any overcenter retention of
the kind that is typical of a pelican hook and to provide a longer moment
arm for the lanyard, and even that is not rated for really heavy loads.

As the other posters have indicated, the real concern will be the crane
operators skill to control the rig when the load lets loose.

By the way, your manual is ready to send. Need a address to send to.

My manual? Perhaps you have me confused with someone else.


--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)

Bruce L. Bergman wrote:

On Fri, 27 Jan 2006 17:35:56 -0600, "Paul G. Shultz"
wrote:

As a crane operator I would not want to drop a 3000 to 4000 pound weight
suddenly. When the weight is released suddenly the boom bounces upward.
Whether or not that results in damage to the crane depends on a lot of
variables including capacity of crane, skill of the operator, hydraulic
or lattice boom crane. It would not be considered safe practice.

There /are/ quick release couplings that will easily work for that -
for a lead on them contact Jamie Hyneman (sp?) at M5 Engineering
Special Effects in the San Francisco area - AKA 'Mythbusters'. They
used them as the drop latch on the "Elevator Of Doom" episode, among
others.

The only way I (NOT a trained crane operator) can see it being safe
to suddenly release the load like that is if the crane is Massively
Oversized for the lift & drop - like a 100-ton monster that is used
for heavy construction instead of a tower crane, and usually has 200 -
250 feet of boom on it. But for this you take every removable section
out of the mast so there's the anchor end and the 25' stinger end,
period.

And even at that, I'd call P&H or Lorain and ask their engineers.
You break one of those puppies, and the parts are not gonna be cheap.

Another piece of parachute technology would be a tear strip (not the correct
term--been a long time)--two pieces of webbing stitched together with a
known stress to tear the stitching--lets one control the acceleration at
both ends to a significant extent so that the weight is not released
instantaneously. Often used to control opening shock. In this case could
be used to prevent a sudden movement of the boom, but the downside would be
that the car has to be lifted higher to hit the ground at the right speed
since its acceleration will be restrained.

-- Bruce --


--
--John
to email, dial "usenet" and validate
(was jclarke at eye bee em dot net)

Which alters the point how? Or perhaps the point that escapes you is that a
By the way, your manual is ready to send. Need a address to send to.


My manual? Perhaps you have me confused with someone else.



My error. Wrong J.