A swing bridge is a movable bridge that has as its primary structural support a vertical locating pin and support ring, usually at or near to its center of gravity, about which the turning span can then pivot horizontally as shown in the animated illustration to the right. Small swing bridges as found over canals may be pivoted only at one end, opening as would a gate, but require substantial underground structure to support the pivot. In its closed position, a swing bridge carrying a road or railway over a river or canal , for example, allows traffic to cross. When a water vessel needs to pass the bridge, road traffic is stopped usually by traffic signals and barriers , and then motors rotate the bridge horizontally about its pivot point. The typical swing bridge will rotate approximately 90 degrees, or one-quarter turn; however, a bridge which intersects the navigation channel at an oblique angle may be built to rotate only 45 degrees, or one-eighth turn, in order to clear the channel.
This column's recent photo quiz featuring the rudimentary swinging bridge over the Murrumbateman Creek near Helm Wines Roadside Treasures , March 25 prompted a number of readers to ask how many other swinging bridges are in our region. With their design based on ancient Inca rope bridges, nothing evokes a sense of adventure more than being greeted by an old rickety swinging bridge in the back country. Now while I can't be sure of the exact number in our region, as many are on private land, this week I went in search of our most photogenic swinging bridges; from those in country settings like the two beauties which span the Goobarragandra River on the Hume and Hovell Track near Tumut to the striking red suspension bridge over busy Belconnen Way. My only criteria for my quirky quest was that the bridge needed to be primarily for pedestrian access, not for vehicles. While this ruled out the famous Hampden Bridge in Kangaroo Valley, I was still kept busy wobbling across a variety of crossings on rickety wooden slats, often just metres above icy waters. Here are my Top 5.
The inside story of how the Swing Bridge was built as it turns 150 this year
The vast majority of bridges that people are aware of are fixed in their position and are so well integrated into the road structure that they become part of the scenery. Fixed span bridges are normally the preferred choice as there is no interference to the flow of traffic, no maintenance of machinery and a reduced risk of collision from ships. The alternative to a fixed span is to change one of the spans so that it can be opened to allow shipping to pass upstream and downstream. For a fixed span bridge to allow ocean going ships to pass beneath, a clearance of 70 metres is normally required.
The swinging bridges built in are the last remaining suspension bridges in Miller County Mo. These are a must see when your in the area. Great fishing and swimming can also be enjoyed here at the bridges including a picnic area. Still in use daily built around Bring your camera.