Question about Cranes. The large machines next to skyscrapers, not the birds.?
344700
They can build a column of girders and then hoist themselves atop it. Then once the column is up, they hoist the cross member atop that. Don't forget, there is an engine in the crane. And they can weld things to the girders and all that. So if they need to raise the height of the column they are on top of, they can weld on secure tie points, attach a cable to them and lower the crane with a winch. They don't have to lower it all the way to the ground. Then they can extend the colun by the girders they previously winched up there, which are supported by the column they are on. If this is confusing, try searching for time lapse films of construction. You will see what I am talking about.
1021613
No, in fact that had been talked about.  \n\nOne tower had too much on the roof to allow a helicopter to land.  The other had a heli-pad but I think it wasn't serviceable.
183743
No straight answer to this one. It depends 'exactly' what you define as a building, and whether you count masts and aerials that are on the top blah blah blah.\nHave a look here though for more information::
1076324
I dont think superstrength is all its cracked up to be...  I mean any heavy lifting can be done with a machine...\n\nNow flying or x-ray vision -- Now we're talking!
1063847
There is no proof. All the evidence disappeared to China or the bottom of the ocean. Why were they so quick to get rid of that steel? Do you really believe that jet fuel gets hot enough to collapse an I beam? Hell, I've picked out beer cans after a bonfire. Duh! And as far as I know, airliners aren't made for knocking down buildings. They are light so they can fly. Have ever seen a crash site? There usually isn't a whole lot of recognizable things left. A building that would collapse after getting hit like that wouldn't pass a NYC building code exam.
597479
That the crane should lift, at the most, this weight.\n\nIf it lifts beyond its capacity, there could be a catastophic failure.
449839
What type of crane are you interested in learning about?
968693
They are social creatures and likely to hang out where everyone else does - like people!  They tend to gather in flocks too.  If it's near intersections my guess would be that's because it's between two clear fly zones, where there are not tall trees or buildings to get in their way as they fly.  They like to stay relatively close to the ground for warmth, water, food, action...and wires are everywhere so they are used to hanging out there.  \n\nAnother thought...People are not going to bother them or threaten them if they are sitting on electrical or telephone wires - those birds who sat there learned that, and the birds who chose the buildings and windowsills didn't fare as well.  The survivors spread the wisdom to their offspring (a Darwinian explanation, but makes sense even if you're not a Darwinian).
36379
I speculate it has to do with the auto industry moving their assembly plants out of Detroit (offshore?).  The abandoned plants were still around in downtown Detroit when I visited in 2003, it was quite depressing.
526639
yeah, a HUGE new tower bigger than both the original towers..\n\nIts called the Freedom tower, see link:\n\nhttp://www.lowermanhattan.info/news/revised_freedom_tower_reflects_16531.asp
973618
I'm not 100% familiar with this but this should be pretty close to the answer.  Simple/standard crane motors work by applying power first through a rotating steel shaft into a gearbox.  The gearbox allows the gearing ratio to be changed (to trade rotation speed for torque or torque for rotation speed).  Another steel shaft carries the power out of the gearbox, again through rotation, to a spindle (think big thimble) around which steel cable is wrapped.  So the motor rotates this spindle to wind in the cable or unwind the cable to lift things or lower things.\n\nHere is a good page on cranes:\nhttp://en.wikipedia.org/wiki/Crane_%28machine%29\n\nHere is a good page on motors:\nhttp://en.wikipedia.org/wiki/Electric_motor
697499
they are pulling it down so i guess demolition cranes???\n\nbut i do not have Google Earth so i wouldn't know, but if it the same thing that i just checked on google maps. i am right hehe
1011022
Safe Working Load of a crane.
11953
Wings are not welded on to Jumbo Planes.  Wings are structurally integral with the rest of the aircraft frame.  There is a big 'skeleton" of structural metal under the skin of a jet.
430653
When you look at a tall tower crane, the whole thing seems outrageous -- why don't these structures fall over, especially since they have no support wires of any kind? \nThe first element of the tower crane's stability is a large concrete pad that the construction company pours several weeks before the crane arrives. This pad typically measures 30 feet by 30 feet by 4 feet (10 x 10 x 1.3 meters) and weighs 400,000 pounds (182,000 kg) -- these are the pad measurements for the crane shown here. Large anchor bolts embedded deep into this pad support the base of the crane: \n\nSo these cranes are essentially bolted to the ground to ensure their stability. In the next section, you'll learn how tower cranes "grow." \n\nTower cranes arrive at the construction site on 10 to 12 tractor-trailer rigs. The crew uses a mobile crane to assemble the jib and the machinery section, and places these horizontal members on a 40-foot (12-m) mast that consists of two mast sections. The mobile crane then adds the counterweights. \nThe mast rises from this firm foundation. The mast is a large, triangulated lattice structure, typically 10 feet (3.2 meters) square. The triangulated structure gives the mast the strength to remain upright. \n\nTo rise to its maximum height, the crane grows itself one mast section at a time! The crew uses a top climber or climbing frame that fits between the slewing unit and the top of the mast. Here's the process: \n\nThe crew hangs a weight on the jib to balance the counterweight. \nThe crew detaches the slewing unit from the top of the mast. Large hydraulic rams in the top climber push the slewing unit up 20 feet (6 m). \nThe crane operator uses the crane to lift another 20-foot mast section into the gap opened by the climbing frame. Once bolted in place, the crane is 20 feet taller! \n\nOnce the building is finished and it is time for the crane to come down, the process is reversed -- the crane disassembles its own mast and then smaller cranes disassemble the rest.
425200
Bulldozers, Cement Trucks, Cranes, Cement Rollers, Trucks, Plowers, etc.
785975
In the US most are called Tower Cranes and they actualy lower them selves down part way then using Mobile Cranes they diss asemble them the rest of the way