This bridge was formerly the property of the Chicago Rapid Transit Company and the Logan Square line operated over it before the Dearborn Street Subway was bored. It was left in place since signal lights are now hung from it.
Found an answer to my own question:
http://www.forgottenchicago.com/tour.php
It is the fourth or fifth set of photos down, just below the photo of Fascination Candy Co building, pretty easy to distinguish. Nice concise description. Thought I’d share.
Mike
Paul beat me to it![bow]
Me too! And his answer was probably a lot better than anything I could have supplied.
Its been 40+ years since I took high school physics, and mudchicken will correct my incorrect terminology, but the counterweights usually have to be much heaver then the bridge they are lifting as in many cases, the are like see-saws, on the short side. If I remember anything about levers, and I don’t, for equal lift weight, in half the distance the weight would have to be twice as heavy. Now that I have shown off my physics ignorance, someone will correct and add to this.
Counterweights exist for balance, not leverage. The mass on each side of the trunnion has to be equal and the trunnion is located at the center of gravity in order for the span to remain at a given position. Since the span is only being moved around the trunnion, the motor needs to be strong enough only to move the mass and overcome the friction involved.
If the counterweights were heavier than the span, a downward force equal to the excess weight of the counterweight above the span would be required to keep the span in the lowered position.
Think about that a bit more. He’s right, of course-- more mass on a shorter lever arm means a balanced bridge.
Now you got it. (The exception would be bridges like the ones in Chicago, where the counterweight and the bridge are pivoting around two different trunnions.)
A very neat boat ride which I have never taken, but it is on my list of things to do is the Water Taxi from North Michigan Ave to Chinatown and return. I just missed it in August and didnt want to wait another hour.
Also, there is a great little fish shack on 95th street at the bridge, called Calumet Fishery. I dont like smoked salmon but the GF does and she swears by it. I have had their fish and fries and it was good. The NS mainline is just south of this and it is a neat area, if you like industry, boats, trains, and bridges.
ed
On two occasions I’ve taken a pleasure-boat ride on the Michigan/Chicago/Calumet triangle (think about the names, and you’ll get the picture). Got sunburned both times, but also came back with fantastic experiences in both sights and history.
Ed, I know the shack whereof you speak–not sure I’d like smoked fish, either, but recall that whatever it was I had from there (shrimp?) really hit the spot.
I didn’t know you could take the slow boat to China(town). That would be a neat trip. I guess you wouldn’t go as far as the Amtrak lift bridge, though.