Double-beam drawbridge
The road surface is connected to the bottom hinge close to street level.A rotating arm, the balance, is attached to the portal high up off the ground.The drawback of a traditional double-beam drawbridge is that it has a limited clearance height.When the pivot point falls behind the column, the tower is loaded eccentrically; this gives both pressure and flexion.The rack is often not straight, but with a curvature at the end, like a hockey stick—this is to give the electric motor time to rev up and gradually raise (and lower) the bridge.
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