Engineering Problem or Stupidity

The driver couldn't estimate the height, what's he blind???

Here I thought my Grand dad pulled a boner when he caused a black-out in down town Denver,Colorado in the late '40s, when the boom of his crane he was hauling snagged and ripped out the over head street car power lines at 17th and Broadway during rush hour. He told me he had some really pi$$ed off people to deal with over that one. That was a couple years after he cut the main telephone trunk between Lowery Air force Base and the Pentagon in 1943 during the height of WWII. He was contracted by the Army Air force to clean and grade the Highline Canal that ran through the base, but they didn't tell him about the Communication cable, (it was top secret at the time). Claimed he never seen so many MP's with machine guns at one time! Turned out the Base Commanding General was on the phone with the Pentagon at the time!

Great stories. Thanks for sharing. I rejected a job excavating in a landfill site near a town when the insurance companies had a one shot premium to undertake the work worth almost as much as the total job. But if you had to evacuate people and jobs without insurance, it would break the business. Someone tendered way too low, but I don't think they understood environmental insurance issues for this specific job. They got lucky as nothing serious happened. I did not like the risk.

I had also once driven on a road where a small backhoe struck a train underpass. It knocked the backhoe off the flatbed into the path of an oncoming car. The results were not nice and a fatality occurred. The truck driver was charged. I was detoured around the site.

We had a similar problem while building a gas station. While digging the hole for the fuel storage tanks we discovered a underground vault that no one knew about. Not unusual to find unknown utilities when digging on a construction site.
That was the strangest phone call I ever received from a contractor. I answered the phone and he said he was surrounded by secret service.
Apparently the government had a very secure communications line running through the property that no one was supposed to know was there.

We have a local air base that services the missiles in our state and every now and then someone digs up one of their 'secret' lines while doing excavating or on a few occasions as the stories go simply working a field.

Yep everyone I have heard about got the full on military response as well.

The only thing that makes any sense to me is that somehow this boom must have been improperly secured but lowered when put on the flatbed. During transit it raised somehow and bang.

How do you repair this for $134K, this appears to be a mono pour of concrete, with a single support column in the center. How do you "patch" this and maintain the ability to support the moment and shear of anything but bicycles.This looks like at a minimum one half the structure to be rebuilt.

FAKE - The concrete op top anticipated the accident and jumped out of the way.

the boom does not even show wear.

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etc.

How do you figure that? Are you looking at the pictures from your phone?

The hydraulic cylinders are ripped apart. All the hydraulic lines on the boom plus their brackets are ripped clean off and there is a big kink in the main boom just below the elbow pivot point.

Open the last picture in a new screen and do a bit of zooming in. You will clearly see a huge amount of damage done to some very heavy high strength steel components!

Clearly the boom went in to the bridge frame just below the side rail where once it had made it past the first 10 or so feet it started to get levered back and up puncturing through the bridge deck.

As it continued to fold back and go up it ripped up the remaining decking until the main boom reached full height pulling the whole machine off the trailer and slamming the cab into the bottom the bridge and the whole rig came to a stop.

Nice forensic analysis.....

http://www.pashnit.com/forum/showthread.php?t=6918

It went through the railing without damage.
If the boom was in a flatter position at first how did the hook survived?
Did the concrete on top jumped out of the way?

It didn't go through the railing. It went under it and pushed through the bridge floor completely missing the railing.

That's not a hook. It's the structural steel block the bucket curling cylinder used to be attached to. Physically it's a incredibly solid part. So solid in fact that the bucket cylinder and pins sheared off before the steel block gave up.

I have spent a good deal of my working life around large excavator machines like this so I know how they are designed and built. I have no feelings whatsoever that these are fake. Those machines are built solidly enough that one could be rammed through a concrete bridge like this and come out looking as seen in the pictures.

I'll add that heavy machinery components like the excavator arm are not made of hardened steel, that would be too brittle. They need to be annealed so that they deform before they completely fail.

If the parts were hardened, during an overload condition they would be likely to crack catastrophically. You really don't want a joint or pin to fail when you are lifting a heavy load, especially near people. Annealed parts are softer and will deform and stretch under overload. This failure is much easier to see and fix before the part catastrophically breaks.

This doesn't mean the parts aren't strong, it just means that they have their limits.

While I was looking in the NTSB accident reports to see if they had any followup reports, which they didn't that I could find, I did find this bizarre story. I don't know why I don't remember it happening but it was May 15, 2004 and unfortunately it proved fatal for a 3 member family. After re-reading this report, it's hard to believe how everything unfolded.