An excavator is a construction vehicle used to dig or move large objects.It is made up of two parts:a driving base and a powerful boom arm with an attachment desigined for digging.The operator sits inside a small cab attached to the base and controls the arm. The base has two sets of articulating tracks that are attached to the side of the excavator.The tracks oprater like wheel to move the unit,but provide a large surface area that creates in a more stable base for the machine.On top of the base is a plarform that rotates between 180° and 360°. The opetator sits inside the cab and has two sets and controls.One sets moves the actual unit forward and backward,and the other set moves the unit on the horizontal plan and controls the arm.These controls determine the angle and speed of the movements of the arm and bucket along the vertical axis. An excavator is designed foe use on construction sites and is quite expensive to purchase.Many smaller construction companies lease or rent these units to avoid the expensive overhead costs.The lease and rental rates vary,depending on the length of the contract,and the volume of the business with the leasing firm.The more equipment that a company leases or rents from the same firm,the better the pircing will be. All oprators are required to obtain a license for the safe operation of this machine.Failure to obtain this qualification can result in a construction site being closed by the workplace health and safety inspector until a valid certificate holder is available to operate the equipment.In addition,many insurance policies are void if the equioment is not operator. Excavators come in a wide range of sizes and capacities,and the heavier the unit,the greater the lift capacity will be.Some are small enough to fit through a standard doorway,while others are much larger.The most important factor for a person to consider when looking at smaller excavators is the amount of workgroup movement.The greater the degree of the move.

TRACK ROLLER The purpose of track roller is to transfer the weight of the chain to the ground and roll on the tracks.In order to prevent derailment,track roller  should also prevent the track from moving horizontally relative to it. Track roller often works in mud,water and sand,and bears strong impact,the working conditions are extremely bad,the rim is easy to wear. The requirements of the support wheel are:wear resistant rim,reliable bearing seal,small rolling resistance and so on. CARRIER ROLLER The functon of carrier roller is to keep the chain track in a straight line.If the carrier roller is damaged,the track chain track cannot keep the straight line. Carrier roller is a one-time injection of lubricating oil,if there is oil leakage can only be replaced,in the work should try to aviod supporting wheel long time immersion in muddy water. SPROCKET The sprocket is a transfer force,can change the speed of rotation,can change the direction of rotation. IDLER The excavator front idler is used to guide the track to turn correctly to prevent it of running of track and deviating.Most excavators also play the role of a heavy wheel. In this way,the contact area between track and ground can be increased and the specific grounding pressure can be reduced. The wheel surface of the guide wheel is made of smooth surface,and there is baffle ring in the middle as a guide,and the torus on both sides supports the rail chain. TRACK CHAIN The tightness of excavator track is is like the size of shoes worn by pepole,which must be adjuster to the best state to move forward.In the working operation of excavator. It often causes the change of crawler's tightness,and the tightness of crawler also determines the wear degree of the chain to its contact accessories. TRACK CHAIN ASSEMBLY The track chain assembly is composed of two parts:the track shoe and track chain,and the two parts are joined together by bolts and buts.