"john" wrote in message
...
Joseph Gwinn wrote:
In ,
"Steve wrote:

wrote

Part 2..

http://www.youtube.com/watch?v=A4v9N...eature=related

bigger crane to remove smaller crane from house.

Using a protractor, I come up with a boom angle of around 35 degrees.
And
it looks like the boom is pretty much fully extended. I wonder how
experienced the operator and supervisor were. That's a rookie mistake.

There was a distinct SNAP! sound, followed hy the Holy ****! What was
the snap sound?


I would bet that the support for the outriggers was defective but I
cannot see the condition of them in the video. It is not uncommon for
the outriggers to sink when they are not on solid firm ground. If that
happens the crane is going over if the load is not near the ground. The
operator should have had a measurement of how far he was going out with
that load because that is the most important dimension. The crane should
have been placed closer to the garage to decrease the distance where they
were installing the pool. He should have also made a test pick at a
distance from the center of rotation to where the pool was going plus
another 5 feet to make sure he was not exceeding the limits of the crane.
HIgh loads are a bitch if they are swung too fast. Centrpedal force will
add to the moment on the boom and can topple the crane. Once it starts to
go with a high load, hang on cause you're going over.
At least they were smart enough to use two other cranes to remove the
crane from the house, one just to keep it from slamming down after the
other crane picked up on the boom. Weight times distance, very simple
highschool physics, and then check the charts that are supposed to be
inside the cab of the crane.

John


Joe Gwinn

I think that the cracking or snaping sound heard in the video was the
concrete driveway suddenly failing under the rear outriggers of the crane.
In the second video, in several of the frames it looks like the driveway is
crushed under the outriggers. It's hard to see because unfortunatly there
is a big damn cardboard box in the way. As the load was moved farther away
from the crane the load on the rear outriggers would constantly increase
until the, typically, thin concrete of the driveway suddenly failed. This
sudden "lurch" could then have initiated the tipping over of the crane.