Pontoon bridge in 638. The army of the Umayyad Caliphate built a pontoon bridge over the Bosporus in 717 during the Siege of Constantinople (717–718). The Carolingian army of Charlemagne constructed a portable pontoon bridge of anchored boats bound together and used it to cross the Danube during campaigns against the Avar Khaganate in the 790s. Charlemagne's army built two fortified pontoon bridges across the Elbe in 789 during a campaign against the Slavic Veleti. The German army of Otto the Great employed three pontoon bridges, made from pre-fabricated materials, to rapidly cross the Recknitz river at the Battle on the Raxa
Suspension (vehicle) Mini. A number of different types of each have been used: Traditional springs and dampers are referred to as passive suspensions — most vehicles are suspended in this manner. The majority of land vehicles are suspended by steel springs, of these types: Automakers are aware of the inherent limitations of steel springs, that they tend to produce undesirable oscillations, and have developed other types of suspension materials and mechanisms in attempts to improve performance: The shock absorbers damp out the (otherwise simple harmonic) motions of a vehicle up and down on its springs. They also must damp out much of