GREAT INVENTIONS (CONSTRUCTION MACHINES)

Building the base of new roads and buildings requires removing a lot of dirt and lifting a lot of weight. The stones and the earth are extracted with excavators and dump trucks of very powerful engine. Some parts of these machines are hydraulic or pneumatic. Construction workers also use hand tools, such as wheelbarrows.

An excavator has a shovel to open wells and ditches, driven by an arm moved by hydraulic pistons. Instead of wheels it has caterpillars, so as not to sink into the mud. The excavator is operated by a driver from the cabin.

A pneumatic hammer has a cutting tool that hits the ground. A pump called a compressor injects air into the cylinder to push the piston down. When the piston reaches the bottom, the compressed air escapes and a spring pushes the piston upwards. The result is a very fast movement.

A hydraulic piston uses a liquid, which can be oil, to move a piston inside a cylinder. The oil is pumped in and out of the cylinder, which moves the piston and, consequently, parts of the machine, such as the arm of the excavator.

A pneumatic machine uses air to move the pistons up and down in a cylinder. The movement is transferred to other parts of the machine, such as the tip of a pneumatic hammer.