Crane tip-over.

[Dalmatian90]

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.

...

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.

You're right on the vector mathematics, but you're using an overly simple formula for this example.

T=r*F*sin(a)

T = torque
r = distance
F = force applied
a = angle between the distance (the crane's arm) and the Force (the downward pull of gravity)

When you apply a force perpendicular, the angle = 90 and thus the sin(a) = 1. So T=r*F is true, because it's equivalent to T=r*F*1. That's your basic torque wrench since you apply you're arm's force to the handle at 90º.

With the crane at 45º, the calculation is:

T=100' * 10,000# * sin(45) = 707,000ft-lbs

With the crane at 70º, the angle between the downward force of gravity and the boom is 90-70=20º, so the calculation is:
T=100' * 10,000# * sin(20) = 342,000ft-lbs

So with the boom at 45º, you have about 365,000 more pounds of rotational force being applied then when the crane is at 70º.

Now those examples are somewhat simplified -- in real life we have some additional weight from the boom to take into account; the pivot point of the crane may not be where the boom meets the platform; and you have factors like shock loading, wind loading, and the momentum of the object when rotating the crane to take into account. But the single biggest factor is the angle of elevation of the boom and the weight of what is being lifted.

 

[Hoister]

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.

#1 your right

#2 Incorrect ..Scoping the boom in and out only leads to intemediate boom lenghts and reduced capacities..Cranes have a load chart determined by the manufacturer..the boom lenghts are all predetermined and are normally better than intemediate boom lenghts ..because of the angles involved ..
#3 dont confuse a crane to a telescopic fork lift ..they are not the same ..

 

[Hoister]

Dalmatian90

In a nut shell ..thats the point ..

In the past Ive used the "screw driver opening a paint can " anology ..the longer the driver the easy it is to open the can ..

 

[Adkpk]

John, doesn't elm have to be debarked, burned or buried in that area? How about the wood, it makes fabulous furniture. I know you were just subbing, but hope it went to a better use than firewood. Here, there's at least three craftsman that take urban woods.

These guys are huge

www.urbanhardwoods.com

Wow, nice web site.

 

[lego1970]

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.

Yes, sadly all I have is an 8th grade education and even then my math level is more like 5th grade. Having said that I believe I could learn math but I do not have the time nor money to hire a tutor to help me and also the school courses I've checked into are already too advanced for my level. Therefore, I can only try to visualize physics and geometry in my head without numbers. Thanks anyway for trying to explain it.

 

[corsair4360]

The simple rule of thumb is that any crane has the maximum lifting capacity next to the center of pivot or pin where the load is transferred to the ground. The greater the distance from the pin, the lower the capacity.

For instance, a 300 ton crane that was on our heavy construction job site many years ago was down to 170 tons at 180 feet from the pin, not your average crane and not the average lifting job by any means. That crane was many truck loads (a Manitowoc 4600 ringer) just to get it on the job site.

All cranes today have lifting charts in them for safety so the operator has some idea of the limitations of that machine. The big challenge with a tree section is what does it weigh, and that is no easy task unless you stay conservative. Wood density is quite variable within a species and highly variable between species. Better estimate the number of cubic feet in the lift and use a conservative estimate of the weight per cubic foot before attempting a lift. Overloaded cranes are really dangerous, as this example shows.

If you are experienced with crane work in the area and the species involved hyou are better off, but estimating the weight is something that it is easy to get wrong.

 

[lego1970]

I did a little small scale test so I could visualize what is happening and from what I could tell, Pdqdl is correct. I think maybe where I was getting it wrong was because in most situations you try to get the truck as close as possible to the load and shorten the distance and in doing that a lot of times the boom has to be raised to do that. From that I guess I was getting the center of gravity part wrong in thinking that the angle of the boom was affecting it. Now as others mentioned the boom can probably handle more weight when it's being compressed rather then bent, but I guess that doesn't affect the tipping of the truck?

I took my son's toy fire truck and put it on a flat wooden chair with a empty milk jug hanging from the end of the boom. I positioned the boom off to the side of the truck, and lowered it so it was completely horizontal, and it stuck outwards 12" with the telescoping part completely retracted. 3oz of water was it's tipping point. I then raised the boom to 45 degrees and extended it's telescoping part so it was again 12" from the side of the truck and once again 3oz of water was it's tipping point. I did the test three times and the results were the same everytime. Granted this is a small scale test, not excact in measurement, and there is probably a lot more to it, but I think the small scale test was close enough to prove Pdqdl right.

I don't like being wrong or not able to understand things but I guess life is a never ending learning process. I have a "Physics Made Easy" book which I really like because it's filled with drawings and gives me a visual to try and understand things but as I said, I can't do the math. However tommorow night my neighbor (who's a construction supervisor and good with math) said he would try to show me the math towards this subject. I hope I can figure it out because this would be good info to know for both tree work and when I'm hauling flatbed.

Great Post!

 

[treevet]

You're right on the vector mathematics, but you're using an overly simple formula for this example.

T=r*F*sin(a)

T = torque
r = distance
F = force applied
a = angle between the distance (the crane's arm) and the Force (the downward pull of gravity)

When you apply a force perpendicular, the angle = 90 and thus the sin(a) = 1. So T=r*F is true, because it's equivalent to T=r*F*1. That's your basic torque wrench since you apply you're arm's force to the handle at 90º.

With the crane at 45º, the calculation is:

T=100' * 10,000# * sin(45) = 707,000ft-lbs

With the crane at 70º, the angle between the downward force of gravity and the boom is 90-70=20º, so the calculation is:
T=100' * 10,000# * sin(20) = 342,000ft-lbs

So with the boom at 45º, you have about 365,000 more pounds of rotational force being applied then when the crane is at 70º.

Now those examples are somewhat simplified -- in real life we have some additional weight from the boom to take into account; the pivot point of the crane may not be where the boom meets the platform; and you have factors like shock loading, wind loading, and the momentum of the object when rotating the crane to take into account. But the single biggest factor is the angle of elevation of the boom and the weight of what is being lifted.

I am still waiting for OD to get into this discussion (lol). Hey this is all Greek to me as well but I can certainly read a load display and chart and approximate the weight of a piece.

But I think the variable you all are ignoring is the holding power of a sliver (see top of remaining trunk) of oak wood. And the shock load and downward recoil force applied after it responds to this shock when it suddenly detaches. There is a lot less finesse involved with a huge crane like this as compared to a small 30 or less ton crane when feeling this resistance prior to it popping off. Kind of like using a surf casting fishing pole to catch small crappies. And the length of the boom with the jib attached and boomed all the way out and hanging significantly on a downward angle would accentuate this recoil.

Note the piece remaining on the top of the trunk.

 

[treevet]

This was a highly technical removal done very skillfully up to this point. Just shows how one little mistake or error in judgment can ruin everything

 

[treevet]

 

[treevet]

And again you have to wonder why this tree was removed....

 

[Adkpk]

And again you have to wonder why this tree was removed....

I agree 100%. Is there no protection for trees like this one in that State, county, or town? If not who's asleep at the wheel.

The home owners must be from outer space not to see the value of a specimen such as the one that caused the demise of their cozy llittle abode. I feel no sorrow for these people myself. It's as if God willed it this way.

I do hope there is some investigation as to why and who decided to remove it.

I know in most of the towns I work in that tree would not be allowed to be cut without a permit. Meaning certain landmark trees are protected by the town and carry a hefty fine if violated.

If I was in charge on this one I would make sure that that tree company (Atlas) was monitored as to what they were proposing to remove for a few years until they prove they are on the right track to "tree care".

 

[ROOTSXROCKS]

The uppermost cut on that trunk looks mighty funky to me, too much up, sudden release, dynamic jump cut!

Something about that cut aint right?

That crane was plenty big enough, and then some.

jomoco

The tree looked like an amazing specimen of an Oak. I don't want to jump to conclusions, but taking out an amazing tree like that must have taken a lot of sweet talking by the salesman. Looking at the before shots you cannot even see any dead wood up in the canopy.

The $10,000 for the removal could have purchased years worth of preservation on that grand old tree. From pruning, to Cobra, to fert and spray for any affliction under the sun. The economic climate is tough, but trying to scare people into unnecessary tree removals is LOW. Really low, and I hope that we can all work hard to keep our business a float, and our moral standards high.

There was a picture in my local paper up here in Eugene Oregon.

I was on a job site in Logan Utah back in 2005 when a 90' crane tipped. The boom punched a hole in the neighbors roof and crushed the brand new cedar fence and shed. The plan was to pic the top 30' off of a 70' cottonwood using a snap cut. The cut did not snap easily so more tension was applied, when it finally snapped the tree bounced up and shock loaded the crane. Tipping the whole rig over. The climber/owner of the outfit was out of the tree and was lucky he was. The boom scraped down the side of the tree where he had been and his rope still was. He would have been nothing more than a skid mark down the side of the tree had he not exited the tree.

It is a surreal experience see something like that happen. I know I will not ever forget that day, it is stored in High-Definition.

Be careful out there.

"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 ....

Exactly, I now see it clearly, the operator of the crane was tugging a little to hard when it gave way.
I didn't see this other topic prior to my post on the second one. this now makes much more sense.

Perhaps the two should be merged

I compleatly agree the tree should not have been removed, I saw no danger that outweighed the value of that tree

 

[NCTREE]

That looked like one beautiful tree, it's kind of disgusting to see what people will do to serve their wallets.

 

[Taxmantoo]

I compleatly agree the tree should not have been removed, I saw no danger that outweighed the value of that tree

I saw no danger that outweighed the danger of the crane, anyway.

 

[tree MDS]

If you use the search function here and punch in "sudden oak death", member mantis posted a link to an article regarding SOD. Now I can understand why it may have been a possibility that that tree did need to come down.

 

[jomoco]

:greenchainsaw:

If you use the search function here and punch in "sudden oak death", member mantis posted a link to an article regarding SOD. Now I can understand why it may have been a possibility that that tree did need to come down.

Your honor I object!

Pure hearsay on counsel's part, with no corroborating evidence!

Move to strike from the record sir!:greenchainsaw:

jomoco

 

[tree MDS]

:greenchainsaw:

Your honor I object!

Pure hearsay on counsel's part, with no corroborating evidence!

Move to strike from the record sir!:greenchainsaw:

jomoco

Gotcha.

You would, of course have to send a cutting or some :censored: off for testing to be sure is what your saying right? Lol.

 

[jomoco]

Gotcha.

You would, of course have to send a cutting or some :censored: off for testing to be sure is what your saying right? Lol.

It's an excellent example of instant karma taking a big juicy bite out of the entire range of agonists responsible for the forced euthanasia of one of the community's most venerable senior citizens.

That magnificent oak probably only needed a few cables to support it's co-dominant heads up top to last another century! It appears to have been lovingly maintained for 150 years up till now.

If that tree was healthy?

Removing it was a crime in my opinion!

jomoco

 

[Blakesmaster]

If that tree was healthy?

Removing it was a crime in my opinion!

jomoco

I wouldn't go that far. I'm a big advocate of personal property rights and think the HO absolutely has the final say in that decision and if they wanted to hire me, I'd do it. However, if the HO's were talked into removal with shady tactics and fear mongering that is another thing entirely...