Crane tip-over.

[John Paul Sanborn]

I can make that circular cut around the spar with either the top or bottom of my bar TV, and yes I leave it idling in the cut alone when I need both hands to spin my lanyards around the spar.

Even standing on the ground making my base cut, the cutting procedure itself is the same, crane side first, then walk around to the release point.

Remember I'm talkin fat wood here in the 40 inch plus range.

jomoco

I've noticed that my big wood cuts a very similar to a Koos Bay. I'll start 1/3 in on the right side, go to the left side to do the same, then rock around on the dogs to get 1/3 on the back before cutting to separate. I've done this on leaning stems that I did not think would jump off too.

The evolution of my doing this was cutting ears with a short bar. I used to start on the left side, but I said WTF I'll get the right side started while I'm here.

Another one I relearned from an "oldtimer" (~15 years my senior) for chunking. Make the back cut 90% to you and the bottom cut is real small and will snap off with ease. Very good when you need to control the separation.

 

[treevet]

I can make that circular cut around the spar with either the top or bottom of my bar TV, and yes I leave it idling in the cut alone when I need both hands to spin my lanyards around the spar.

Even standing on the ground making my base cut, the cutting procedure itself is the same, crane side first, then walk around to the release point.

Remember I'm talkin fat wood here in the 40 inch plus range.

jomoco

I can see it on the ground for sure but sometimes that saw is gonna want to vibrate right out of the cut in the air when you don't have a hand on it.

We got some big wood around here too. Last year I removed a Bur Oak that was an 11 foot 11 inch ground cut and yesterday I made a visit to a 510 year old Bur oak that is not long for this earth that I have worked on and off over the decades (and so have the storms) that has about a 7 foot dbh. We had to cut it in half about 7 years ago when it squashed a house (previous co. had put in too small dia cables that broke in a down shear) that was 140 feet tall that, again, I had to cut in half due to other splits in co doms. That was an interesting crane job. 10,000$ and half of it is still there and that was a fair price it was so dangerous.

 

[John Paul Sanborn]

Except for willow we rarely see really big wood. That elm on TV was exceptional, it survived because it was down in the valley. With the storms that come off lake Michigan most tall tops are self pruning, which was why the elm came down.

 

[pdqdl]

This picture pretty much tells the whole story:

NO IT DIDN"T!

When I posted the original message, it had a picture of all the cranes from the helicopter view of the whole scene. Somebody somewhere pulled a fast one on me, and now I can't edit the original post!

This message is intended to keep you guys from thinking I am some sort of retard, although it is probably too late for that!

 

[Hddnis]

NO IT DIDN"T!

When I posted the original message, it had a picture of all the cranes from the helicopter view of the whole scene. Somebody somewhere pulled a fast one on me, and now I can't edit the original post!

This message is intended to keep you guys from thinking I am some sort of retard, although it is probably too late for that!

I just thought you were being clever about saying that they all ended up looking foolish and getting unwanted coverage in the media. lol


Mr. HE

 

[lego1970]

I saw the original crane pic you posted, and wondered why it changed.

 

[treevet]

I saw the original crane pic you posted, and wondered why it changed.

I'll give it a go again......

 

[tree MDS]

Anyone know who's ins. co. would have to pay for that house??

I can imagine the ins. companies fighting over it while the HO's are burning up dealing with red tape/staying with the relatives. I had a lady's trees get killed when the neighbor's garage burned up (and some minor damage to her house), her ins. finally paid themselves...but it took 6 months to get settled.

 

[John Paul Sanborn]

http://abclocal.go.com/kgo/story?section=news/local/north_bay&id=7123327

Here is some TV footage. The story says that it was a 50 ton capacity. Looking at the pictures it was jibbed out, so it might have been down to a few k-lbs with the boom down that far. I just cannot see that rig being a 100 ton capacity, maybe the 100 tone quote is the vehicular weight.

http://www.youtube.com/watch?v=cDLEaAqbfbY&feature=channel

here are several other vids on YouTube, It looks like the OE may not have been able to see the size of cut that was being made....

 

[oldirty]

guess who just found this thread.


let me read through before i start firing off on some of it.

although we wouldve been in the driveway that pick wouldnt have done us wrong like that.

i'm guessing he thought he hooked a phat large mouth bass and was giving her all he had and when the cut finally got finished she popped right off the stem the same way a hooked bass leaps out the water.

nice.....crane talk.

 

[Dalmatian90]

Anyone know who's ins. co. would have to pay for that house??

Tree company is the general contractor. They should make good the loss to the homeowner.

The tree company & crane company no doubt will file claims against each other. Crane is probably the biggest loss in the picture, the two insurers will want to know what % of responsibility they bear to know how much their share to pay is.

I'd bet most Homeowner's policies cover this as well, but they have such a strong subrogation claim to make against the contractor, the contractor's insurance probably prefers to just pay directly rather then go through the Homeowner's.

 

[pdqdl]

I can see what the problem was.

Somebody misjudged how much the crane could lift, but then the operators errors stood out.

That boom was way too high, and way too long. When the load tipped the truck up, the huge amount of boom shifted further out as it went down, gaining leverage and weight (relative to the fulcrum point). The truck, on the other hand, lost weight and leverage as it went up.

Before very long, the boom outweighed the truck and it didn't stop accelerating downward until Mother Earth caught it.

If the boom had not been up at a steep angle, the dynamics would have been different, and it would only have pulled the boom down until the log hit the earth, then the operator would only have needed to feed out the winch to lower the truck.

It may well be that those cranes are not supposed to be operated at lower angles, though.

 

[lego1970]

I can see what the problem was.

Somebody misjudged how much the crane could lift, but then the operators errors stood out.

That boom was way too high, and way too long. When the load tipped the truck up, the huge amount of boom shifted further out as it went down, gaining leverage and weight (relative to the fulcrum point). The truck, on the other hand, lost weight and leverage as it went up.

Before very long, the boom outweighed the truck and it didn't stop accelerating downward until Mother Earth caught it.

If the boom had not been up at a steep angle, the dynamics would have been different, and it would only have pulled the boom down until the log hit the earth, then the operator would only have needed to feed out the winch to lower the truck.

It may well be that those cranes are not supposed to be operated at lower angles, though.

Not trying to argue with a neighbor, but the steeper the angle the more you shift the center of gravity back onto the crane and more lifting capacity you have so the general rule of thumb is to always keep your boom as verticle as possible, instead of worrying about how to recover from a mistake.

 

[pdqdl]

Well, sort of. By keeping the boom as vertical as possible, you keep the load as close to the truck as possible. Then torque is reduced for any given weight. But when the boom is up higher than necessary to reach the same distance from the crane pivot point, it increases the amount that the booms swings away from the truck when it's capacity is exceeded.

All cranes are engineered around a certain torque capacity. The torque applied to the truck is the same for any given load, whether the boom is low to the ground, or the jib is extended way up. The only thing that counts is distance from center x total weight= torque.

Exceed the torque capacity, and you will tip every time. Extend the boom too much, and it increases the risk of a load becoming unstable and exceeding the capacity. This is clearly what happened on this job, since the boom kept falling to the ground long after the log hit the ground and was no longer pulling down.

 

[Hoister]

"That boom was way too high, and way too long.
Yes a crane is a inherently a first class lever
Your concept of the boom length and angle in regards to the latest generation mobile hyraulic crane is incorrect..

The newer hydraulic cranes,such as the one involved in this incident ,gets its capacity on the elevation of the boom when rigged with jib. The main boom is made to bend and compress.. A lower angle means the boom has less structural integrity due to bending.. the higher main boom angle means the boom is now compressed more so than bent and a higher structural integrity is achieved ..allowing for a greater capacity at a large radius..
More over at that radius, its a certainty that full on main boom capacity was lesser than the capacity main boom less a section with the jib erected ..



As in one article a gentleman from Procrane was quoted as saying "A shock load started the whole thing"

the crane capacity was 7600lb's ,the load supposed to be 6000lbs..not a bad deal if it's coming of the ground versus mid air ..
I wasn't in the seat but when that load drifted of the trunk ..there was two sudden load moments ..Based on the loads and capacities as they were reported

the first was the crane getting the load ..boom deflection made the whole thing deflect and also increased the radius ..
..but the crane didn't go over then ..it sat there lurched and groaned ..but she didn't go over at that point ..

the second :As the accelerated load lost its momentum against the resistance of the crane..the excessive deflection of the boom that was generated means the boom began to back up accelerating the load back up ..then as the boom stopped deflecting up it deflected back down under its own momentum.. giving slack to the load ..the load then changed direction accelerated towards the ground this time with enough force to haul the machine over ..because simply the whole boom had a downward momentum and the rest of the crane had also changed from a static position to a dynamic position ....

 

[Hoister]

Not trying to argue with a neighbor, but the steeper the angle the more you shift the center of gravity back onto the crane and more lifting capacity you have so the general rule of thumb is to always keep your boom as verticle as possible, instead of worrying about how to recover from a mistake.

depending on the load ..more boom can offer a greater radius..Because the boom is being compressed versus being bent ..

Thats the basic concept and your right ..

 

[lego1970]

PDQLD,

If you place the boom only as high as needed to reach the load and keeping a short leash on it via the winch your boom angle will be greater and therefore shift the center of gravity away from the truck. If you raise the boom as high as possible and lower the cable to the load you are shifting the center of gravity back towards the truck. I understand your point about the higher up it is, the more the load would swing before it hit the ground and yes that would compound the problem. Also while I couldn't tell from the pics it looks like the the white ladder extension is out but the cable is not being lowered from that point and I believe once the telescoping part is extended the white extension can't be swung back and stowed away like it normally would be, so if that is true I don't know how much that would take into account.

 

[Hoister]

The main hoist was over the lattice extension ..the sheave is up and the line is out, the crane was working of the jib ..theres no question ..

 

[pdqdl]

Nope. That is not how it works.

In fact, by extending the boom out, more metal is further away from the truck (thereby moving more weight further out), and the tipping capacity for any given distance and weight is reduced.

Torque is what tips a crane over. It is only a two dimensional consideration, since all the forces are governed by gravity. EVERYTHING is straight down.

So the math involved with tipping the crane is simple: distance from center point x weight of the load=torque. Exceed the torque, and over you go.

An example might be a 10,000 lb log 100' feet away from the crane. If the tipping torque of the crane is 1,000,000 lbs, then it will tip over when extended out while picking up the log. Why? The weight of the boom will add to the weight of the load, and it will exceed the tipping torque limit. The hook won't stop going down until the applied torque is reduced.

It will not matter one little bit if the boom angle is high with lots of cable, or low with a short cable. The log still applies 1,000,000 foot pounds of torque onto the crane.

If you want to look it up, do some research on vector mathematics. You probably forgot, but they made you do that stuff in the 8th or 9th grade.

 

[pdqdl]

Hoister, I think you might have some expertise here. Feel free to pitch in.

While it is provably true that the boom angle does not determine the torque applied to the crane, I suspect that there may be other reasons that a crane operator might want to keep the boom angle high.

1. I suspect the boom itself is a bit stronger in a more vertical position.
2. Extending the boom in and out is a bit slower to operate than tipping up and down. This might be a big advantage when moving wood back and forth.
3. The greatest wear point on the crane structure is on the sliding contacts between the boom sections, so the crane will have lower maintenance if the operator does not go "in and out" any more than necessary. This is particularly true for the multistage hydraulic cylinders on the inside, which are OMG expensive to get fixed.

Conversely, the hydraulic cylinders have a reduced weight load on them when the boom section is carried lower, so less strain on the lift cylinders. I have a little 12k knuckleboom crane, and it will stall under load as it goes up higher, since our hydraulic system is a bit worn.