Excavators are machines to loosen and load of soil in a continuous or step-by-step way. As long as the extraction takes place in a wet environment, they are called dredging machines. Cable excavators use a cable and winches to use the tool, hydraulic excavators move the tool using a hydraulic transmission.
Excavators are usually moved using a hydraulic drive for driving, moving and working.
The running gear is either constructed with wheels or caterpillars. Heavy machines always have a caterpillar due to the better distribution of the forces into the soil. Light and medium sized machines can also be built with a wheel drive (up to 30 tons, 130 kW and 2 m3 shovel size). This enables the machine to drive fast.
Many factors influence the performance of an excavator:
- the consitensy of the soil - the shovel layout and dimensions - the available force of the machine - the position, size and ability of movement of the machine - the size ration of the shovel to the truck volume - the construction site's efficiency
The cycle time of an excavator consists of the four parts
- filling the shovel - moving of the full shovel - emptying of the shovel - moving of the empty shovel
The bulking of the soil is an important factor, e.g. rocks have a very high bulking whereas the bulking of sand and gravel is very low.
The fill factor of a shovel depends on the soil. The more cohesive a soil is, the higher is the filling factor.
The performance of an excavator can be calculated with
L (scm^3/h) = V * ff * fa * n * 3600 / t
t = cycle time [s] V = volume of the shovel [m^3] ff = filling factor of the shovel  fa = bulking factor of the soil [solid cubic meter / loaded cubic meter] n = efficiency factor of the construction site.
t = 35 s V = 2 m^3 ff = 1.1 (Sand) fa = 0.9 (Sand) n = 0.75 (45 min / h)
leads to L = 152 solid cubic meter per hour