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Anonymous Poster

How to increase the height of tower a crane ?

06/01/2008 1:03 AM

Hi Everyone

Could anybody clarify me as to how the height of towers cranes are increased as the building becomes taller ?

Thanks & Regards

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Anonymous Poster
#1

Re: How to increase the height of tower a crane ?

06/01/2008 1:09 AM

They don't in New York City...

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#2

Re: How to increase the height of tower a crane ?

06/01/2008 4:28 AM

They have cranes that can jack themselves up as a new section is installed beneath.

There must be a video clip of it somewhere....

Del

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#7
In reply to #2

Re: How to increase the height of tower a crane ?

06/02/2008 9:41 AM

Thanks Del, I will try to find out the video clip ------

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Anonymous Poster
#3

Re: How to increase the height of tower a crane ?

06/01/2008 7:52 AM

Hi friend, To increase the height of tower crane section You must use a jacking cage. Jacking cage put in between the TC section, jacked it and then insert the new section. Thats all. But after The TC reach its Free standing height, You must tied it to the building column or beam, we call it "Ties". "Ties" normally made of H Beam and its function is to hold the section from turning when the TC jib turned around, and it will also reduce buckling effect due to the section length. Thanks

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#4

Re: How to increase the height of tower a crane ?

06/01/2008 9:23 AM

I got to see this as they were building a high rise nearby. They have a sleeve about 20 feet long that they slide up over the frame of the crane. They connect the frame to the sleeve at the bottom of the sleeve, then break the frame inside the sleeve and jack it up about 10 feet, then they slide in another section of frame through the side of the sleeve. They attached it to the frame, and jack it up, and repeat.

My dimensions are probably wrong, but you get the idea.

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#8
In reply to #4

Re: How to increase the height of tower a crane ?

06/02/2008 9:43 AM

Thanks a lot for the answer --obviously the procedure looks pretty difficult and risky.

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#10
In reply to #4

Re: How to increase the height of tower a crane ?

06/02/2008 11:50 AM

Ohh Myyy..It's very interesting how they do it definetly. No argue with ya' on this one. Very informative. Awesone is the word I bet. I dont know this one but someone told me that they also sometimes make use of the same access thruw the building from bottom / up to install the pass elevators through it after crane been removed. Unbelievable!

Hey Buddy that's a real cool Doggy there it really look very nice one. Congratulations.

Hanging in There,

MC

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#5

Re: How to increase the height of tower a crane ?

06/01/2008 10:17 AM

Check out this site,

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#6
In reply to #5

Re: How to increase the height of tower a crane ?

06/01/2008 10:51 AM

And what about this bad boy?

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#9
In reply to #6

Re: How to increase the height of tower a crane ?

06/02/2008 9:45 AM

Thanks Bruce for both the Sites --both are quite informative.

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#11
In reply to #6

Re: How to increase the height of tower a crane ?

06/02/2008 12:15 PM

I suspect these sites will be visited frequently given the rash of crane failures worldwide. Has anyone checked out the math on the strength calculations for these bad boys?

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#12
In reply to #11

Re: How to increase the height of tower a crane ?

06/02/2008 12:19 PM

You can be sure that someone has. But it wasn't me!

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#13

Re: How to increase the height of tower a crane ?

06/02/2008 5:39 PM

Hi, Guest!

Overnight, the crane crew uses hydraulic jacks to raise the level of the crane body by adding a section or two. However, this height must obviously be very restricted, or the crane tower would buckle, overbalance and fall.

So, at building growth intervals, depending upon the type of crane being used, the base of the crane is frequently relocated to newly finished and weight-bearing floors as the building goes up. The cranes you see on the skyline are not anywhere near as tall as the buildings they are helping to create. They're just a few floors high before rising their operating distance above the top storey. Some a few more, and some a few less.

The idea that they rise from the bottom floor through the top of very tall buildings is as outlandish from a structural steel point of view as it is from a construction efficiency point of view that ludicrously assumes that floor finishing crews are expected to travel down through dozens of floors to complete the forming, concrete, and rebar the crane has been endlessly assembled through as the super-high crane is dismantled. The reality is just as interesting, but much less dramatic.

If you ask the crew of a construction crane for permission, they may very well be happy to let you watch the process.

Mark

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#14
In reply to #13

Re: How to increase the height of tower a crane ?

06/02/2008 7:49 PM

Hello MarkTheHandyman,

I think this crane goes all the way from the ground to the top. This is the one which failed in March 2008 in New York City.

The lower picture shows a huge tower crane which also rises from the bottom all the way up.

These cranes are situated outside the building, so they can more readily be dismantled when no longer required.

But there is also the type which you have described where the support rises with the building (probably the majority of cases).

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#15
In reply to #14

Re: How to increase the height of tower a crane ?

06/03/2008 3:31 AM

Would not the second picture more properly be called a gantry, not a crane?

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#16
In reply to #14

Re: How to increase the height of tower a crane ?

06/03/2008 3:42 AM

Hi, ba/ael!

The crane that collapsed in NYC was the visible working portion of a 60 meter, or 180 foot-long crane arm, including counterbalance. It was being used in a building that had completed just 25 stories of a new Manhattan high rise. The height of the crane tower was not given, but after the engineering forensic report is done, quite probably had very little to do with the collapse. The crane tower in the picture showing an external skeleton is about 125 feet high by nine to ten feet in width and has a working arm about 75 feet long with a counter balance arm of about 45 feet; about 60 feet shorter than the one that fell. It's unlikely to be raised much higher than it was when the picture was taken and the new building's structural steel shows it to be about sixty feet (six storeys) high.

Mark

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#17
In reply to #16

Re: How to increase the height of tower a crane ?

06/03/2008 4:38 PM

Deaammmnn! You guys do know this stuff real good Buddy's. Awesone learning always here at CR-4 with the Masters overhere gosshh! you have the technology!

Now about that crane material composite what will they used ?

Reinforced Steel or some differents alloys, like titanium ?

Anyway it has to be real solid whatever in it, and somehow flexible at some grade I assume.

Next thing a CR-4 brand new building, hehahe.. All set hang in there now.

Strong Deal,

MC

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#18
In reply to #14

Re: How to increase the height of tower a crane ?

06/03/2008 5:27 PM

Hi, ba/ael!

The piece of crane that fell in New York was the 180-foot working portion of the crane, not the total tower. When the engineering forensics for the accident are published, we will all find out why the tower buckled. But you can be (almost) certain that the accident was caused by faulty connections involving the working section of the crane, not the length of the tower. The building from which it fell had only 25 storeys completed. [Quite probably the crane was already stationed on or above the 15th floor -- just a guess, of course, until I can find out more for you.] The second picture of the outside crane tower has a working crane about 75 feet long with a counter balance of about 45 feet long. The very small building (about 50 ft X 100 ft) it is working on will not be much higher than the six or so storeys it is now. The crane tower shown is only about 120 feet high with a 10-foot width.

Again, if you want to see how these things are done, a crane crew might very well be willing to allow you to watch overnight as they work.

Mark

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#19
In reply to #18

Re: How to increase the height of tower a crane ?

06/03/2008 6:40 PM

Hello MarkTheHandyman,

Yes, I guess you are right. Here are some dimensions of the big momma I referred to earlier.

It would clear about 250 feet, not enough for a skyscraper. So the tower has to be raised as you go. And the building has to be designed to resist the tendency for the crane to overturn.

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#20
In reply to #19

Re: How to increase the height of tower a crane ?

06/04/2008 3:17 AM

Hi, ba/ael!

I don't know whether anybody else experienced the same view of your last blog as I or not because on my monitor, the picture got imposed over the writing, but you stated,

"Hello MarkTheHandyman,

Yes, I guess you are right. Here are some dimensions of the big momma I referred to earlier.

It would clear about 250 feet, not enough for a skyscraper. So the tower has to be raised as you go. And the building has to be designed to resist the tendency for the crane to overturn."

If the building floors are level and built to code, the crane would still be very carefully levelled on the floor by its crew. I don't recall for certain, but I don't think the crane is butressed by any connections to the intervening floors up its tower length. I think that the 250-foot high crane tower has to be an exception, not the rule. 17 - 25 storeys is quite a long crane tower, and if it is that high, one would wonder when and how its through-floor passage gets sealed up after it is raised. I'd hate to be the site supervisor on that site.

Mark

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#21
In reply to #20

Re: How to increase the height of tower a crane ?

06/04/2008 10:38 AM

Hello MarkTheHandyman,

I'm not sure why the picture was superimposed over the writing on your monitor because it appears okay on mine. This time I will put the picture below the text and hopefully it will work better. Below is a page taken from the climbing crane instruction manual on the last high-rise project I was involved in. It illustrates what you were saying with the tower rising as the building progressed.

A horizontal force must be transmitted to the upper and lower floors as shown. A vertical force acts on the lower floor. These forces must be carried by the building.

There was a rectangular steel ring at each floor where the tower was anchored. The ring was blocked against the edge of the concrete slab using heavy timbers. A couple of WF beams carried the vertical force at the lower tower floor.

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#22

Re: How to increase the height of tower a crane ?

06/04/2008 9:17 PM

There is a "cam" that will lift (or rise) up, one section directly under the cab of the crane (or where the operator sits). The cam lifts up and the operator wheels in a new section of the "mast(?)" to be bolted in place by iron workers (hopefully Union). It is a really cool sight to see. The initial crane is built by another crane (think of a truck type of a crane) that sets everything in place for the initial construction to start. As the need for more altitude grows nearer, the operator and the ironworkers work as a team to increase/decrease the heighth. DIAGRAMS DO IT NO JUSTICE. It is a sight to see...

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#23
In reply to #22

Re: How to increase the height of tower a crane ?

06/05/2008 2:07 AM

Hi, Ferris!

I suppose that given the number of expressions of belief that cranes just rise into the sky from the ground up there may be some substance to it.

The initial setup of the crane sometimes (also?) uses this technique of having the crane tower [mast] raise itself section by section after the working portion [jibs] is pre-assembled (for the most part) on whatever floor is ready when street-based cranes no longer can easily supply the materials for forming, with an assembly system run by the crane operator and new sections installed under the cab.

The self-added sections you report to be used to increase the height of a crane past (I think you mean) more than just initial setup, lead me to guess (nature of special fasteners that would have to be used aside) the additions must be calibrated for size to within thounsandths of an inch so they never install even a little bit off-center...a technique moving the crane from floor to floor can avoid because in that case there will be --after the pre-balanced crane has reached working height-- no need for adding more sections.

Mark

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#24
In reply to #23

Re: How to increase the height of tower a crane ?

06/05/2008 9:53 PM

I do not know about calibrations or any thing... I do know that the guys up there (Ironworkers and Operators alike) when they are adding/taking away the new segments of the upright (tower?) part of the crane have my utmost admiration and a big pair between their legs. There have been a few of these cranes that have toppled in the past couple of years. Either when the load is going up or down (as they are raising or lowering the platform section, or the jib), ya know the extra pieces going up/down, in/out that we are talking about...

cheers

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#25
In reply to #24

Re: How to increase the height of tower a crane ?

06/06/2008 1:40 AM

Hi, Ferris!

By 'calibrating', I was referring to the careful measurement and settings applied to any piece of technical equipment to make it work accurately. Calibrating is fine-tuning. You can calibrate anything from a spectrometer or oscilloscope to a torque wrench, just to make sure that when you use it, it's as accurate as can be. Precision equipment, like pianos, require periodic calibrating on a scheduled maintenance basis. (I just had my micrometer torque wrench calibrated last year. There's a company in the Toronto area whose entire business is calibrating torque wrenches of every type, make and size. I couldn't believe the complexity and size of some of them ...they probably cost a small fortune! )

If even one of the sections of a tower crane built from the ground up to a great height is just a hair off being directly below the one above or being centered directly over the one below, it can geometrically multiply a tiny little bend over a number of lengths that would cause the upper part to move past its balance point or become 'top-heavy', buckle and topple over. That's why I gave the example of having to be thousandths of an inch in exact line below and above.

It's also extremely difficult to imagine doing this with [relatively inexpensive to produce and purchase] sections of crane body, because the calibration equipment and the time required to do the job --with the enormous precision I guess would be required to ensure safety-- would just be impractical. That's the other reason I gave that example.

But if the crane were just completely built in a few sections, properly balanced for its size and height at the beginning, and left at that single unchanged height except to be raised to a new floor from time to time (checking the balance each time), the calibration of each new section would be unnecessary, and using the crane would be much more practical in terms of the time and trouble it would take to elongate it otherwise. And that's the other reason I gave that example.

Yes, the crane operator can raise the jibs using a built-in elevator to a position one crane mast section higher than it had just been, then pick up a new section and place it next to the mast to fill the gap left behind. Crane crews then place the new mast section in the vacancy, and up she goes. But practically speaking, there is a limit to how far up she goes before she only goes up again by being raised to another completed floor from below with hydraulic jacks. You can imagine what the difficulty might be if new sections were just added time after time right from the ground up: that's some pretty major weight distribution and balancing up there on those jibs with only a few nice tight beam chords --and assembled ones at that!-- keeping the thing afloat. For sure, you wouldn't want it tipping or waggling! (That might be a sine of destruction! Sorry, couldn't resist!)

I've never been fortunate enough to be personally around at the very moment when the crane operator is actually doing the elevator thing, just seen it on video.

But I've been around crane crews who do the moving up to new floors. It takes a fair amount of time to assemble the new platform and calibrate it, move the crane up and check the settings, and tighten it down; and it's amazing how rapidly experienced crews can do the deed. That's why it's done overnight. I always breathe a huge sigh of relief after it's done, and can't wait to get out of there. If it's still up the next day or two later when I come back, THEN I trust it'll probably work properly there. And, strangely enough, it does!

Mark

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#26

Re: How to increase the height of tower a crane ?

06/06/2008 5:44 AM

OF INTEREST TO THOSE WHO ARE CURIOUS ABOUT THE CRASH OF THE NEW YORK CRANE IN MARCH OF THIS YEAR

[Here is the part of the preliminary engineering forensic report May 30, 2008 about the collapse of the crane in NYC this past March, prepared by the New York City Office Of Emergency Management which, as I had indicated in my blogs above, has also come to the conclusion that it was not the mast that fell, but rather the jibs and operating platform only:]

"Tower Crane Assessment

The Buildings Department and the engineer of record for the crane have determined that the tower mast attached to the new building under construction at 335 East 91st Street is secure.

Forensic Investigation Report

The preliminary investigation indicates the crane cab, boom, and machine deck separated from the tower mast and collapsed onto the street after hitting the building at 354 East 91st Street. The tower crane was not being jumped, erected, or dismantled at the time of the incident. Preliminary reports indicate the tower crane was being used at the time of the incident by the crane user (concrete subcontractor), Sobara Construction Corporation. Buildings forensic engineers and inspectors are investigating the cause of the accident."

[Let's look at the news of the crash through the eyes of media reportage (and perhaps learn something about media reportage credibility):

If, as indicated by the news stories below, it's true that a piece of steel fell immediately prior to the accident, it's evident that the steel came from somewhere 'above', (or nobody would have seen the steel "fall' --if indeed they saw anything at all--) and I think if there was one, it probably was either a component of the mast/jib connection or of one of the jib's beam chords, either of which may very well then have separated the entire jib structure under the strain of imbalance.

It is interesting to note that the media were in agreement with several of the bloggers here who thought that the collapse might have included the mast. Some media observations, including those of "engineers" (more likely bureaucrats in positions of authority in various construction companies) who were theorizing on possible causes of the collapse well before the facts were all in (and didn't we all?? ), follow. Even the mayor was misinformed.

Pieces of News Articles about the New York crane crash follow: ]

· "The incident occurred when a third collar was being attached to the year-old Favco 440 after it had been climbed, according to James Lomma, president of crane owner New York Cranes. He said that the collar slipped, and knocked out two lower collars that attached the tower crane to the building. Without any connections to the building, the crane toppled over. The crane was about 200ft (61m) high when the accident occurred. The crane fell on top of nearby buildings on 50th Street.

Lomma added that he did not know why the collar slipped, but he said that the crane climbing operations were carried out by a construction subcontractor. Investigators are pursuing a theory that one of the fabric slings holding the collar snapped.

[ The building was reported as being +/-19 floors done, which would have made its finished height between 190' and 285'. If the crane was based on the ground floor when the accident happened, it would only have reached up to the 13th floor. This crane had not yet, apparently, been 'climbed' [raised to a new floor, or 'jumped']. The purported 61 meter tower on a swivel base would have been passed at least 30-45' through the minimum group of three floors required for it to have three collars on it, leaving a minimum of 150' above the last finished level for working... probably a third more height than it needed. It's extremely unlikely that a falling collar from the top floor hole would dislodge a fixed collar 10 – 15' (a single floor) or even 20 – 30' (two floors) below by falling on it, so only the top finished floor of three in the building through which the crane mast passed would likely be the one to remain unsupported; and under normal circumstances, how much could the mast have bent until it hit the sides of its hole through the top floor and knocked off the jibs, etc.? Very little. If the collar that came off was from lower floors and not been the very top collar, the crane could not have bent at all. No mention appears in the preliminary forensic report about collars or slings.]

" About 19 of the high-rise condominium building's 43 planned stories had been erected, and the crane was scheduled to be moved Saturday so workers could start work on a fresh story when a piece of steel fell and sheared off one of the ties holding it to the building, according to Stephen Kaplan, an owner of the Reliance Construction Group, which manages construction at the site. The crane had been given a clean bill of health on Friday and a permit was issued to workers for Saturday."

[Shearing off a tie would presuppose that the mast toppled, which it apparently did not; and that a crane based upon a turntable would be tied to the building, which it would not. Of course, the reporter could have asked what a 'collar' is, and misunderstood it as a tie. Since the crane had been operating for –apparently-- some time at the same level (and was expected to continue there until "Saturday", it's unlikely that a collar could just 'fall off' or even be wrenched off under duress.]

· "The collapse occurred", the mayor said, "as workers attempted to jack up the crane, raising its height to enable work to continue above the 19th floor of a planned 43-story building." Builders had city permission to raise the crane, and the crane had been inspected on Friday, with no violations found. The collapse occurred at 2:22 p.m. as the crane, about 22 stories [220 – 330'] tall and attached by girders to the apartment tower under construction at 303 East 51st Street, east of Second Avenue, broke away from its anchors and toppled south.."

[As we have seen the crane was not being jumped and the purported "22 storeys" of the crane did not topple.]

· "Forensic experts will be focusing on a particular weld that failed…" acting Buildings Commissioner Robert Limandri said in a statement.

[Well, if they did, we haven't heard about it yet…just like we haven't heard yet about the falling collar, the 'snapped off' turntable (below) and the failed tie, all of which were given as the reason for the collapse by various 'authorities' at the time of the crash.]

"One crane expert explained what might have gone wrong.

The house or the turntable, which spins the crane, snapped off for whatever reason, Dan Mooney said; it might have not been balanced improperly. If the crane is unbalanced, it would have a tremendous amount of torque on the bolts and it would just be a matter of time before it could happen. The Buildings Department released updated information on past violations at the site."

[Extremely unlikely that torsion would be applied to stationary bolts holding a turntable as the turntable turned off balance. Perhaps some tensile stress and resulting work wear if the bolts were not properly tightened down hydraulically as they probably were, however.]

"After the March crane collapse, the city … added extra inspections at building sites and required that its staff be on hand whenever the towering cranes were raised higher, a process known as a jump. However, the city changed course on Wednesday…The city no longer requires building inspectors to be present during all jumps. Instead the city said it will conduct unannounced spot inspections. Contractors are now required to notify the city and hold safety meetings before raising, lowering or lengthening a crane."

[The turntable, which comprises the base of the crane, was not reported by forensic experts to have snapped off. They might still report it, but more likely if it had snapped off (engineers would be hard-pressed to explain how the turntable might have snapped off due to stress. The turntable would have been located one or more storeys below the latest finished floor. It would have turned before applying stress on any of its component parts. Stress on it would be limited to the multiplied force of the tower alone acting about the fulcrum of that floor since the jib had separated, and shearing might occur through bolts holding the turntable to a frame, if any existed. More likely, the mast would just bend at the fulcrum or lever the turntable off its floor and break the fulcrum point itself.) A snapped-off turntable would have been reported here in the forensic report, which instead reports that the 'tower' is intact.]

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#27
In reply to #26

Re: How to increase the height of tower a crane ?

07/30/2010 8:26 AM

Nice Post about Tower Crane.I like your post.

Very useful information of Tower crane.

Cranes are used commonly in construction/ manufacturing industry. These are temporary structures, and is either fixed or mounted.

Cranes are usually operator-controlled and some of them are operated by using a push-button control-station or a radio/infrared remote control.

Hoist Crane || Jib Crane

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#29
In reply to #27

Re: How to increase the height of tower a crane ?

07/30/2010 3:57 PM

Thanks, lisaka!

Mark

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#30
In reply to #26

Re: How to increase the height of tower a crane ?

10/02/2010 8:24 AM

Hi,

I like this post so much, Its really useful for me. I like to your ideas about how to increase the height of tower a crane. I like to share some information about crane. Cranes are typically used to move and assemble heavy equipment. Crane sizes run the gamut from the enormous ones all the way to much smaller ones which tend to be used in factories and workshops. There are also really tall ones typically used in the construction of tall buildings.

Thanks for this nice sharing.

Hoist Crane || Jib Crane

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#31
In reply to #26

Re: How to increase the height of tower a crane ?

10/18/2010 9:04 AM

Hello, friend what a nice information sharing in this forum. I like your post so much.It is important that the operator should set the load down first in a stable position and should be detached from the hook before leaving.

Thanks for this superb information.

Hoist Crane || Jib Crane

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#28

Re: How to increase the height of tower a crane ?

07/30/2010 9:36 AM

The diagram below is not the clearest but should give you an idea of the concept. They say "they work to the top from the top".

Also, this video http://www.pbs.org/wgbh/amex/newyork/sfeature/sf_building_pop_02_rm.html doesn't show the detail of raising the height it does show how construction cranes work to great heights and what I found amazing is that it is the original construction footage of the WTC towers. Somewhat eerie!!

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Anonymous Poster (4); AussieBob (1); ba/ael (6); bhankiii (1); Del the cat (1); Ferris (2); kroni (2); lisaka (1); magwer (2); MarkTheHandyman (8); sushil_ind (3)

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