The Principle of Oscillation
With dynamic compaction systems the compaction performance of a roller can be clearly improved. These systems are based on the fact to stimulate the surface by vibrations in such a way that a grain relocation can take place into a closer position. With the vibration compaction the material which has to be compacted is set in vibration by vertical forces in rapid succession. As with the unique Hamm oscillation compaction tangential forces are introduced in the material to be compacted. The drum rests in constant contact to the soil and achieves therefore a faster compaction.
Traditional vibrating rollers are equipped with a circular vibrator in the drum. It effects by fast rotation that the drum begins to vibrate, thereby compaction forces arrive into the soil. With the directed vibrator two moving masses, arranged in opposite directions, are used which cause directed oscillations.
In the oscillation drum masses turning in the same direction, produce one moment around the drum axle. The moment changes its effect direction during a turn of the mass (forward and backward), so that the oscillation drum movement is created. Here thrusts are introduced into the soil.
Minimum oscillation stresses for the surrounding
By oscillation clearly lower oscillation stresses are generated as with the vibration. Here only up to approx. 10% of the stresses in comparison to vibration are created. Oscillation rollers use their performance not to unintended vibration stimulation of the surrounding field, but introduce these specific there where the energy is needed. Low oscillations guarantee a longer life span of the machine and an optimum in driving comfort.
The oscillation system developed by Hamm is not based on complicated mechanical rule mechanisms, but uses alone in an intelligent way the physical laws. Depending upon material rigidity of the underground thereby the amplitude value adapts automatically. That means the amplitude is reduced continuously according to the rising soil rigidity. As the amplitude reduces accordingly, the performance transferred to the soil rises itself...
An optimum at compaction quality
This innovative technology allows the Hamm oscillation rollers practically immediately - within 10 milliseconds - to adjust to changed soil conditions. This corresponds to a distance covered by the roller of only approx. 1 cm. Through those continuously working static load and the changing dynamic shearing stresses in the material, a faster, better and more careful compaction takes place.
Oscillation on all job sites
On all bitumen job sites – from the smallest surface, brides, multi-storey car parks up to highways – the oscillation shows its performance and clear advantages. The oscillating movement in combination with the permanent static load of the drum guarantee a fast increase of compaction paired with very homogeneous compaction and good surface roughness. The sub base remains thereby preserved.
Compaction on bridges becomes just now possible
Oscillation rollers are particularly demanded for bridges. They allow high compaction performance and produce no damaging vibrations. Just on such buildings the bitumen cools down faster by the sea breeze. That is no problem for the oscillation because with oscillation it is possible to work on even lower bitumen temperatures.
Good compaction on joints
At the joint between two driving lanes, e.g. with the renewal of a lane, the oscillation avoids a damage of the other already finished i.e. compacted and cooled down roadway. Also transverse travels are easily possible – there is no danger at any time for the road surface.
More flexibility with the Asphalt temperature
Compaction works are only possible within a certain temperature range, depending on the kind of the used bitumen. Starting from a certain temperature the vibration cannot be used any more, it then develops tear or other damage. With oscillation the temperature range is widened around nearly 20%, i.e. the oscillation roller can still continue to work and ensures therefore a higher flexibility on the job site.