Oscillation: A wide variety of applications
For more than 35 years, HAMM has included oscillation rollers in its product range and with over 35 models; it offers by far and away the widest diversity in the world. They enjoy growing popularity on account of their ability to achieve efficient, high-quality compaction at every construction phase. In particular, tandem rollers with one oscillation drum and one vibrating drum achieve at least the same degree of compaction as double vibrating drum rollers, but with fewer passes. Added to this is the low vibration emission. This has made dynamic compaction on bridges, of thin layers and in sensitive areas (such as city centres, rail tracks, industrial plants) possible for the first time. In short: the scope of applications is enormous.
The oscillation principle
In oscillation drums, two unbalance shafts rotate synchronously, driven by a toothed belt. The unbalances are offset by 180° relative to one another. As a result, the drum performs a rapidly alternating forward/backward rotary movement. This causes the drum to direct the compaction force into the substrate tangentially to the front and rear in the form of shear forces. Here - unlike with vibrating drums - the compaction force acts continuously on the substrate because the drum is in contact with the ground at all times. This is why oscillation rollers compact dynamically as well as statically with their intrinsic weight the whole time.
Benefits of oscillation
This type of compaction offers very distinct benefits. They influence efficiency, quality and profitability. These are the most important effects:
Benefit 1: High compaction power – great efficiency
Oscillation rollers compact very quickly. Or to put it another way: their compaction power is very high. The reason for this is the superimposition of dynamic shear forces with the permanent load from the roller’s own weight. As a result, considerably fewer passes are needed, especially on large areas. The use of oscillation has thus also proved its worth on major projects because fewer rollers are needed for the optimised process thanks to the rapid compaction rate.
Benefit 2: Easy operation
HAMM makes use of the laws of physics to generate vibrations in such a way that oscillation rollers are extremely easy to operate. Simply switch on – there’s nothing more for the operator to do. The appropriate amplitude is set automatically according to the rigidity of the material to be compacted. This happens so quickly that compaction is always adjusted perfectly, even with varying substrates. In this way, HAMM has eliminated the risk of operating errors due to incorrect settings.
Benefit 3: Smooth, skid-resistant surfaces
Oscillation rollers produce surfaces with excellent longitudinal evenness. It results from the drum remaining in contact with the ground at all times. Surface rippling, on the other hand, does not occur – not even at high working speeds. Asphalt compaction with oscillation also provides good initial skid resistance, because the oscillating movement of the drum rubs off the bitumen from the top surface of the carriageway.
Benefit 4: Low vibration emissions
Oscillation drums do not lift off the ground while compacting. In comparison to vibrating drums, with oscillation drums only around 15% of the vibration is directed into the substrate around the roller. This means that oscillation rollers can also be used without problems for dynamic compaction near vibration-sensitive buildings or installations. Because the rollers are also much quieter, they help to protect the environment. Another benefit provided by low-vibration compaction is that it reduces component wear and is also perceptibly less tiring for the roller drivers.
Benefit 5: Material-friendly compaction
With vibration compaction, once a certain level of rigidity has been achieved, there is a risk of destroying the material structure or crushing the aggregate. This is not the case with oscillation: it ensures that the aggregate particles are redistributed undamaged. In this way, oscillation avoids detrimental aggregate crushing and over-compaction. Moreover, oscillation compaction produces watertight, long-lasting joints without damaging the cold asphalt.
Benefit 6: Wider temperature window
Oscillation widens the temperature window in which compaction is possible because it can be used to compact without damage, even at lower temperatures. For this reason, oscillation is particularly suited to the compaction of thin layers or on fast-cooling surfaces such as on bridges. Moreover, this characteristic increases flexibility during the construction process.
Contractors benefit from oscillation
Many contractors are aware of the benefits of dynamic compaction with oscillation and know that with this technology, they can not only work extremely efficiently but also increase the quality of highway construction into the bargain. This is the reason why construction companies are increasingly opting to buy rollers with oscillation capability and that today one in five rollers leaving the Tirschenreuth plant sports an oscillation drum.