St. Francisville, IL: Wabash Cannon Ball Bridge

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I have already done a "normal" posting of the Wabash Cannon Ball Bridge. This posting is more of a travelogue of my journey to get my own pictures.

Our GPS routes us down IL-130 through Evansville when we go to Florida, so setting St. Francisville, IL as a destination did not take us too far out of our way. When we approached St. Francisville, we started seeing signs guiding us to the "toll bridge." Unfortunately, we missed the sign pointing us north and followed Main Street east to its dead end at the river.

The "port" sign and the swing span in the bridge reminds me how important canal and steamboat transportation was in the first half of the 1800s when railroads had yet to be developed.

We backtracked and found the sign indicating the left turn off Main Street. The toll was just one dollar. I'm happy to pay a dollar as long as it is used to help maintain and preserve this bridge. (The New Harmony Bridge is an example of tolls going into people's pockets rather than bridge maintenance, and it was closed rather soon after we had a chance to drive over it. And it is evidently still closed.)

When we got to the part of the road that used to be the Big Four branch between St. Fancisville and Vincennes, they did widen the earth fill to be two lanes wide, but just two lanes. There were NO shoulders. (I also see you have a clear view of the splatter on the windshield. But you can see there is no place to pull over to take a clear shot.)

I knew the bridge was just one lane. I did not know there was a trestle over a flood plain that was also one lane.
This is the view to the south about half way across the trestle. So the flood plain is really a wetlands.

We asked the man in the toll booth if there were access roads that would allow us to get a side view of the bridge. He said there was one near the end of the bridge. It was wide enough that we could at least pull off the road. But there was no way I would drive the van down the "access road." But it was an easy walk. (There were some oil tanks just to my right is why this area was "developed.")

I had turned off my lights so that the cars on the other side of the bridge would proceed to use the bridge. This photo not only shows that the bridge is indeed used, it shows the extra width of the pier that holds the swing span.

This is an overview shot from the "access road." Note the long tree trunk running all the way across the picture about a third of the way up. The next picture was taken while standing on that driftwood. You will also find a car in about everyone of these pictures that I took. There was a rather steady stream of cars, especially westbound. (I arrived near evening "rush hour.")

This is the "best shot" that I used at the top of this posting. I had the sun to my back, but once again I'm disappointed in how the pictures turned out. I'm learning that winter shots are shades of brown.

I turned to my right to capture the pile of driftwood that was caught by the trees on the shore. At times the water of the Wabash must get high and fast. This picture also shows the trunk I was on (in the lower-right corner) extended further away from the bridge. When I was younger, I might have considered walking out on that trunk to get a better angle of the truss spans. But it is true that your balance becomes less stable as you grow older. There was no way on God's green earth I was going to walk out over those jagged limbs rather far below the trunk. I might break the camera if I fell.

My wife caught this view as we entered the truss spans. First of all, you can tell it is a Pratt Truss because the thin diagonal members indicate tension forces and the built-up V-lattice vertical members indicate compression forces. Note how light these members are compared to the heavy members of most railroad truss bridges that have survived to the 21st century. Big Four did not use very big steam locomotives on this little branch. But a bridge designed for even small steam locomotives is plenty strong for cars if well maintained.

A view to catch the width of the river that also catches how thin the tension members are. The use of a Pratt truss indicates the bridge is modern enough to be built with steel instead of iron.

I asked my wife to not spare the electrons while we crossed so she included an upstream view as well. You will note that my hands are in the proper 10-2 position. I don't always drive that carefully, but driving over this bridge had my full attention. It was not scary like the Hummer Bridge, but it does hold your focus. Note I had my lights on so that cars on the other side would know it was occupied.

A shot that makes me appreciate that the sun did not catch the spots on the windshield in some of the views. This is probably the east end of the swing span because the members are more heavy duty.

Below I take advantage of a 32-megapixel camera having far more resolution than a web site can use. That is, I digitally zoomed in on the swing span. The heavy diagonals as well as verticals reminds me that it is supported from the center when open and fromboth  the center and both ends when closed. I think this indicates the span is old enough that the engineers really didn't know what was happening with the stresses so they threw a lot of steel at the problem. Another indication that this design is from the mid 1800s is it has two regular trusses hung from a center tower. A swing span built in the late 1800s would have a square tower built over the turntable with four strong compression members at the corners of the tower and the side trusses would not be symmetrical. Examples of the later design is the ICwest and Illinois Northern Bridges.

I include a closeup of the near Pratt truss because it is a good example of how the diagonals, other than the ends, slant towards the center.