Unusual sounds from Michigan Ave. Bridge, Chicago, IL

[JetMechMA]

It sounds like a bearing has seized. Doesn't sound right at all. It also looks like they were testing it, since the other two bridge halfs didn't move...at least during this recording. It's interesting that looking at it from this angle, you can see that they made four seperate bridges and connected two of them to make half of the whole bridge.

[BVictor21]

@JetMechMA

I was most likely a test as no boats passed by during the video. They don't always raise both sides. One side could be under maintenance or something while the other half is fully operational. Also, you'll hear the bridges squeal as they raise.

Remember that the Michigan Avenue Bridge is 90 years old. It's also not raised nearly as much as it once was.

[JetMechMA]

@BVictor21 That's all very interesting. ...that they don't always raise both halfs....I always thought they were both controlled by the same "lever". How very two-dimensional of me. I think I mis-spoke when I said a "seized" bearing....but that sound still doesn't seem right. Where ever that sound is coming from seems like it could use some lubrication. But I know nothing about those bridges.....it's probably been squealing that way for the last 90 years. lol

[BVictor21]

@JetMechMA

Age is some of the factor, but the Columbus Drive Bridge sounds similar (video available) and it was built in 1982. It's just a massive amount of weight that's being counterbalanced.