Green Line Derailments Increasing

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Re: Green Line Derailments Increasing

Postby F-line to Dudley via Park » Wed Oct 19, 2016 4:37 am

BandA wrote:Didn't they screw up ashmont or mattapan turnaround radius?


Mattapan is the system-tightest radius, at 38.5 ft. Only a PCC can take that, so if LRV's go there they will change ends at the platform (double-ended cars not needing to loop at the terminal like single-ended PCC's do). On the loop through the yard the curve behind the maint shed is somewhere between the tight and loose halves of Park Loop in radius, comfortably above minimum design tolerances. Ashmont Loop squeals like a demon because they didn't didn't do a great job with noise abatement on that new concrete viaduct, but the curve radius itself is a relatively generous 65 ft.
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Re: Green Line Derailments Increasing

Postby typesix » Wed Oct 19, 2016 11:58 am

Plus the T years ago got rid of resilient wheels for PCCs, which would have the same effect as the wheel dampeners they bought.
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Re: Green Line Derailments Increasing

Postby Adams_Umass_Boston » Sun Oct 30, 2016 5:17 pm

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Re: Green Line Derailments Increasing

Postby The EGE » Sun Oct 30, 2016 6:02 pm

By pure chance, I witnessed this from just a few feet away. The center truck of #3837 derailed at the switch crossing over from the outbound rail. (They were using that crossover rather than the loop due to separate track work). Here's a couple photos I took; the first was about 3 seconds after the derailment itself.

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Re: Green Line Derailments Increasing

Postby Type 7 3684 » Sun Oct 30, 2016 8:10 pm

Apparently the coupler of 3680 broke as well.
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Re: Green Line Derailments Increasing

Postby MBTA3247 » Sun Oct 30, 2016 10:08 pm

Correct me if I'm wrong, but it looks like the leading truck of 3837 split the switch and kept going on the outbound track, with the derailment resulting from the force from the drawbar rotating the entire A-end over that truck.
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Re: Green Line Derailments Increasing

Postby Disney Guy » Sun Oct 30, 2016 10:21 pm

Was the Type 7 the lead car, the trailing car, or brought in later to help untangle things?

Looks like the Type 8 jackknifed, which could be the result of motors going out of sync. with the back end of the car trying to go faster than the front end.

Reminiscent of the time a Type 8 center truck went up onto a boarding platform and fortunately no one was crushed between the side of the car and the back wall of the shelter
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Re: Green Line Derailments Increasing

Postby KevinSun242 » Sun Oct 30, 2016 10:50 pm

Another interesting read I found on the Type 8's: http://www.mass.gov/auditor/docs/audits/2007/200405837a.pdf
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Re: Green Line Derailments Increasing

Postby F-line to Dudley via Park » Mon Oct 31, 2016 6:14 am

This puts the Type 8 dead line at 12...and that line isn't moving because they've been backlogged at 10 long-term OOS for parts for weeks now. In spite of the 7's being out in record numbers because of the rebuild program, the active rosters are 1:1 dead-even between makes. Which means we're probably going to start seeing a lot more non-accessible 7-7 consists out this winter, as fleet availability is trending in opposite directions.
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Re: Green Line Derailments Increasing

Postby doublebell » Mon Oct 31, 2016 7:07 am

How about a real truck in the middle as opposed to the stub axles?
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Re: Green Line Derailments Increasing

Postby Disney Guy » Mon Oct 31, 2016 8:07 am

With a real truck in the middle there would have to be humps in the floor to clear the axles.

Would just more weight (maybe lead slab dead weight) in the middle keep the middle section on the track better?
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Re: Green Line Derailments Increasing

Postby TomNelligan » Mon Oct 31, 2016 8:10 am

According to a note in the Metro section of this morning's Globe, "The incident happened on the B branch when a Green Line official prematurely threw a switch at the Boston College stop." So that sounds like human error rather than the well-known hypersensitivity of the Breda car middle axles.
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Re: Green Line Derailments Increasing

Postby MBTA3247 » Mon Oct 31, 2016 8:57 am

Where are those switches controlled from? Are they manual or power-operated?
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Re: Green Line Derailments Increasing

Postby The EGE » Mon Oct 31, 2016 10:36 am

The center truck was derailed - the end trucks both stayed on the tracks. I believe MBTA3247 is correct about splitting the switch. 3837 was the trailing car of the 2-car set.

I believe the switch at that location is powered and controlled from a nearby box, but I am not 100% on that. It's not normally used in revenue service.

I wouldn't expect 3837 will be out of service particularly long. It was low-speed, may not have been the vehicle's fault, and other than the coupler there wasn't any obvious damage.
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Re: Green Line Derailments Increasing

Postby F-line to Dudley via Park » Mon Oct 31, 2016 11:44 am

Disney Guy wrote:With a real truck in the middle there would have to be humps in the floor to clear the axles.

Would just more weight (maybe lead slab dead weight) in the middle keep the middle section on the track better?


They tried that during the long, long teething process. Every trick in the book was thrown at trying to weight-balance them. It worked for a dozen years when the components were still fresh and the pristine rail grinding they did to compensate for these fragile trucks was fresh. It was always a likelihood that wear and advancing age was going to make the problems start to resurface. Even if they kept up with the rail grinding that's way, way higher than any other trolley make's tolerance spec...there's only so much you can do to stay ahead of increasing wear on the trucks. And it's not like these things are rebuild age yet; the components aren't shot at all, it's just the design has uselessly narrow tolerances for anything but like-new perfection.
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