Hydraulic cylinders usually answer the call for generating high torque in linear drives. But when rotational power is needed, it’s hard to beat hydraulic motors for high torque with precise speed control.

Whether heavy equipment needs rotational motion for several operations or only one, hydraulic motors often make sense because they can generate high torque from a compact package. But the ease of controlling speed, torque, and direction using simple hydraulic valves makes hydraulic motors versatile, as well.

This report explores examples of different that machines that capitalize on the many advantages of hydraulics to make them leaders within their respective fields.

Hydrostatic Vibration Enhances Compaction

There’s more to surface compactors than what meets the eye. They appear to have a large, heavy drum that rolls across the surface of loose soil or fresh asphalt to compress it down into a flat surface. But that’s not all: They also contain a vibration mechanism that drives an eccentric weight to use force from angular acceleration to apply additional downward force.

The principal works much like compacting soil with your feet. If you stand or walk slowly on loose soil, you’ll compact it with your body’s weight. But if you jump, and stomp on the soil with your feet as you land, the combined force from your weight and leg action will produce much more effective compaction than your weight alone.

In the Model CS56 soil compactor from Caterpillar Paving Products, force from angular acceleration is produced by a hydraulic motor driving a pair of eccentric weights inside the drum. It uses a 30-Hz, dual-amplitude vibratory system to help it deliver optimum compacting force. Changeable from the operator’s station, either of two vibratory amplitudes can be selected to best match the soil characteristics. Centrifugal force in high amplitude is 28,000 lb and drops to 13,800 lb in low amplitude. These medium-duty soil compactors with 66-in. wide drums have estimated production rates up to 500 cubic yards per hour.

Read more: Hydraulic Motors Transmit High Torque for Machine Motion