The unique engineering behind Mystic's drawbridge
The Mystic River Bascule Bridge, built in 1922, has a unique design. On most similar bridges the balance beam that holds the counterweights must remain parallel to the span as it rises. Mystic's bridge, based on a patent by Thomas Ellis Brown, has a pair of linkages that allow the balance beam to rotate through a smaller angle. This means the counterweights do not have to swing all the way down into the supporting structure.