Mobile cranes are conveniently placed on wheels and able to move on their own. These cranes are convenient because they have minimal set up and don’t require special equipment to get the crane to the job site. One type of mobile crane is an all terrain crane, which has 4×4 drive, making it super easy to navigate across dirt and gravel-filled job sites. The wheels can be steered with front-only, rear only, crab, and coordinated steering.
Mobile cranes consist of two parts – the top and bottom section, connected with a turntable which allows the crane to move left and right.
The arm of a crane is called a boom and the booms of our mobile cranes are made of 5 sections that fit inside one another. This telescopic boom can extend to 142 feet, giving workers a lot of height to lift material in a small, compact machine.
Mobile cranes are on wheels, which don’t provide the best stability and can easily tip against the weight of heavy lifting loads. Outriggers are needed to provide stabilization and balance to the truck during a lift. Mobile cranes have 4 outriggers that extend out of the truck sides and stand on the ground, helping distribute the weight of the load and relieving weight from the truck.
Crawler cranes are built a little differently than mobile cranes, as they are not as compact and convenient as mobile cranes. For instance, crawler cranes can not drive long distances and require heavy haul transportation to travel to every job site.
The boom of crawler cranes is a lattice boom, which doesn’t extend into itself, but is made of high strength alloy or steel structures. This causes more difficulties in transportation, as each piece needs to be transported and assembled at each job site.
After it is assembled, the boom has a fixed length and is controlled by a luffer on the back of the crane, forming a little v between the boom and luffer. The luffer controls the movement of the boom, pulling it up or extending it down as needed. Hydraulic power is used to control the hoisting drums, the boom hoist, the swing, and the left and right crawler.
Just like mobile cranes, crawler cranes swing on a turntable. The top section is the crane and the bottom section has a vehicle with tracked wheels. The tracks allow the crane to move around on soft ground and provide a stable foundation for the crane to move around while carrying a load.
HOW ARE CRANES POWERED?
Most cranes have one engine that powers both the crane and the bottom section of the crane. The diesel motors push hydraulics to control every movement of the crane including the control of the boom and the swing movement of the turntable. Crane operators control every movement from their station on the turntable, while project supervisors keep an eye on the crane movements from the outside.
HOW DO CRANES LIFT?
Crane booms work on forces of leverage. The further the boom extends, the less weight the boom can lift as the truck can easily tip, so a lot of engineering goes into each lift. Engineers must figure out exact calculations of how much weight the crane can hold, how far the boom can extend, how high the load needs to be lifted, how tall the boom needs to be, and each turn of the crane. To help lift heavier loads without tipping the crane, counterweights are placed on the truck to balance the weight.
Attached to the end of the boom is a hook, or hoist, that also extends down and attaches to the load or materials that will be lifted. Using hydraulic power, the hoist can be extended back to the end of the boom and be moved where it’s needed.