Hydrostatic drives in heavy equipment

The benefits of using modern hydrostatic components in conjunction with shiftable gearboxes and computer controls include a large control range, precise control of traction effort and speed, and high efficiency.

In heavy-duty applications such as earthmoving, agriculture, forestry, industrial, and mining vehicles, there is a demand for sophisticated performance. Increased overall drivetrain efficiency is also of great importance since the transmission is responsible for 60-80% of the total fuel consumption in most mobile machinery, according to Karl-Erik Rydberg of Linköping University in Sweden.

To attain satisfactory productivity in a wheel loader, for example, a large torque/speed conversion range is required. This demand is quantified by the theoretical range (TR)-the ratio of the highest vehicle speed over the lowest speed in which maximum engine power can be transferred by the drivetrain to the traction wheels (Figure 1). A TR value of 10-15 is often required for a wheel loader. Thus the requirements on the drive transmission in a wheel loader, and many other construction machines, are high.