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
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