Metro says some trains are increasing vibration levels

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Metro says some trains are increasing vibration levels

Postby davinp » Tue Dec 26, 2017 6:51 pm

Residents in some Washington, D.C., neighborhoods said Metro trains are rumbling through their neighborhoods so loudly that their homes are shaking. While they are blaming the newer and heavier 7000 series railcars, Metro said those cars are not the only ones creating a vibrational issue.

The new railcars are built with heavy steel and weigh about 2,000 pounds more than their older counterparts

Metro is still putting together a final report, but a recent letter from Metro general manager Paul Wiedefeld said some newer model trains are increasing vibration levels above Metro standards. However, Wiedefeld said higher vibration levels are coming in above standards with older model trains as well, and none of the vibrations are enough to cause any structural damage.

https://www.nbcwashington.com/news/loca ... 55453.html
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Re: Metro says some trains are increasing vibration levels

Postby STrRedWolf » Tue Dec 26, 2017 8:15 pm

The question is now, is the contract for the 7000 series written well enough that it shouldn't be doing that.
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Re: Metro says some trains are increasing vibration levels

Postby Sand Box John » Wed Dec 27, 2017 8:03 pm

What's amusing about this situation is WMATA and the media in discussing this matter quote the dry weight differences between the 7k cars and their older cousins. When fully loaded any of the cars will have a gross weight north of 100,000 lbs.
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Re: Metro says some trains are increasing vibration levels

Postby smallfire85 » Fri Dec 29, 2017 11:32 am

Sand Box John wrote:What's amusing about this situation is WMATA and the media in discussing this matter quote the dry weight differences between the 7k cars and their older cousins. When fully loaded any of the cars will have a gross weight north of 100,000 lbs.



That is amusing indeed, with crush load design estimates above 120,000. At that scale, you're looking at less than a 5% difference in weight due to the railcar itself.

I've heard an interesting theory that due to other factors in the design that you might get more vibrations out of the 7ks from resonance due to interactions between the frame/wheels/underbody, etc. I personally have experienced instances where the 7ks have a distinct rumble as well as instances where I could not initially tell them apart from the legacy equipment audibly.
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