Construction crews use them to lift steel, large tools, concrete, and more. Although you know what tower cranes look like, you may be curious about how this mystery machine operates. How much weight can it lift? And how do they get bigger as buildings get bigger?
These are just some of the many questions people have about construction cranes. More thoroughly explained, a tower crane is a type of machine equipped with a hoist rope, chains, or sheaves, and used to lower, lift, and move heavy or bulk construction materials around. The work of the tower crane is crucial. Because of tower cranes, we can build large establishments and landmarks in a viable, safe manner. For starters, the base of the crane is secured to a massive concrete pad using large bolts.
This pad will support the crane and make it stable. From there, the base is joined to the mast, also known as the tower. This is the larger tower part of the crane that reaches high into the air. Attached atop the mast is the slewing unit. The slewing unit is composed of a large ring-gear and motor that enables the crane to rotate. Connected to the slewing unit is the jib, also known as the boom. This is the long arm that extends out from the crane. Extending out the opposite direction of the jib is the machinery arm.
It is the shorter arm and contains large concrete counterweights that enable the arm to balance as it extends heavy material along the jib. The operators cab is located on the top of the slewing unit.
This is where the crane professional carefully orchestrates the moving of materials. Although tower cranes can lift and move massive loads at a time, this machine does have its limitations. For the crane transportation process, there are many things to consider when putting a tower crane together.
Transportation Budget The first thing to keep in mind is the Transportation Budget. The transporting of various tower crane components will require heavy hauling services, which naturally, incur additional expense. Transportation Routes Next up is Transportation Routes. Now that we have heavy hauling services for the tower crane parts, we will need to consider road restrictions.
Certain road routes and travels are prohibited when hauling loads that are over a certain weight or dimension. First, the vertical mast is erected. Thanks to it, the jib has a broader range of motion. It contains the computer and joysticks as well as the control systems. The hook block serves as a pulley system that allows the hook to travel up and down the tower.
The counter jib extends in the opposite direction of the jib and helps the tower crane maintain its balance. Counterweights balance the load of the lift. Without them, the load capacity would have to be significantly lower to maintain stability. Some common counterweight materials include reinforced concrete and steel.
The steel used in the construction of a crane is strong and rigid, but even steel has some flexibility. The lean you are seeing is most likely due to that flex in the steel as the various loads are balanced against each other. A tower crane, like most cranes, works on leverage and balance.
One could say that a tower crane is a lever on top of a lever. The jib and counter-jib serve as the first lever balancing the lifted load against the counterweights. If there is no load on the hook, the counterweights will cause the crane to be somewhat unbalanced towards the rear, and the crane will lean backward. As load is applied to the hook, the crane will gradually lean forward due to the shifting balance of the load vs. This is normal and expected. You could see several feet of movement at the top of the crane when lifting a heavy load with a tall crane.
Since the mass of counterweight is fixed, but the load being lifted varies greatly, there is usually some level of imbalance at the top of the crane. This imbalance results in a force at the top of the crane which is then balanced through the tower against the size and mass of the base.
That is, the tower mast is essentially another lever. If the crane base is a concrete foundation, that will be poured as early as several weeks before the arrival of the crane to allow it to properly cure before assembly. Once the crane arrives on site, the first thing to do is build the mast by stacking tower sections vertically. All of the activities above require the use of an assist crane and adequate laydown area to build the crane components on the ground.
If necessary, a tower crane can climb itself to a taller height. To accomplish this, a climbing frame is typically installed at the top of the mast and connected to the turntable.
The crane is then balanced, and the turntable is disconnected from the mast. At this point, the climbing frame uses hydraulic jacks to lift the top of the crane enough to insert another tower section at the top of the mast. This process can then be repeated to climb the crane higher. For very tall projects, the tower crane may also be tied to the structure. Typically, tie-ins are installed as the structure increases in height and then followed by a climbing operation to increase the total height of the tower crane.
The disassembly process for a tower crane is essentially identical to the assembly process, but in reverse order. There are as many tower crane types as there are lifting needs.
Flat top tower cranes are especially useful in situations where multiple cranes swing through the same airspace. The hook is positioned by luffing the jib up or down. This type of crane is especially useful on tight jobsites.
That is, a tower crane must be allowed to swing freely when not in use weathervane. As such, a hammerhead crane requires a clear path around it equal to the full length of the jib. With a Luffing jib crane, the jib is set at a higher boom angle when not in use, which typically reduces the radius needed for weathervaning to less than half of the maximum possible reach.
This is a smaller tower crane that can be erected on site without the absolute necessity of an assist crane. Typically, this type of crane will extend its mast and then unfold its jib via hydraulic cylinders permanently fixed to the crane.
Only a skilled and qualified operator can perform the job safely and prevent any unnecessary mishaps. It can take approximately 10 to 12 semi-trucks to haul in all the components for a tower crane. Mobile cranes are used to assemble the jib first, including the slewing unit and counterweights on the machinery arm.
Once the lattice is in place it is secured and the process with the climber is repeated. View About Welty. We deliver the most extraordinary building experience by never being afraid to do what is right.
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