Needham Line Questions / Discussion

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Re: Needham Line Questions / Discussion

Postby RenegadeMonster » Mon Aug 28, 2017 4:24 pm

What does the shunt do? Show the track as occupied?
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Re: Needham Line Questions / Discussion

Postby Backshophoss » Mon Aug 28, 2017 4:43 pm

The Shunt completes the circuit that shows the track is occupied.
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Re: Needham Line Questions / Discussion

Postby BandA » Mon Aug 28, 2017 11:05 pm

It simulates the steel wheel/axle of the train. Do they double check it with an ohmmeter?
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Re: Needham Line Questions / Discussion

Postby Disney Guy » Tue Aug 29, 2017 8:14 am

Track occupancy sensing using the wheels of the train works like a simple make or break switch to complete the circuit. An ohmmeter would not be relevant except to further narrow down a problem where applying or removing the shunt did not change the signals and indicate the occupancy or non-occupancy.
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Re: Needham Line Questions / Discussion

Postby BandA » Tue Aug 29, 2017 9:47 am

That shunt looked pretty foolproof, but you always want to check your connections.
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Re: Needham Line Questions / Discussion

Postby Trinnau » Tue Aug 29, 2017 6:43 pm

BandA wrote:That shunt looked pretty foolproof, but you always want to check your connections.


They verify proper shunt with the dispatcher.
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Re: Needham Line Questions / Discussion

Postby Stephen » Tue Aug 29, 2017 9:16 pm

BandA wrote:Do they double check it with an ohmmeter?


Watt? I said its 5:00, time to go Ohm.

(Sorry, had to...)
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Re: Needham Line Questions / Discussion

Postby johnpbarlow » Sat Sep 02, 2017 9:44 am

No Saturday service today on Needham line due to PTC installation per status sign at Needham Heights.
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Re: Needham Line Questions / Discussion

Postby johnpbarlow » Sun Sep 10, 2017 9:48 am

Today's PTC installation work at Needham Heights involves Dagle Electrical Construction installing wood utility poles at the station - no idea for what purpose. Also track barricade is erected at the station platform facing a hypothetical inbound train. Interesting that on one rail, the barricade's metal cross piece sits on an insulating rag presumably to not shunt the track circuit?
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Re: Needham Line Questions / Discussion

Postby BostonUrbEx » Sun Sep 10, 2017 6:21 pm

The poles are to hang up the fiber optic communications cable on.
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Re: Needham Line Questions / Discussion

Postby NeedhamLine » Mon Sep 11, 2017 10:40 am

The trackside poles now extend all the way from Needham to Forest Hills - I take the Needham Line daily and it surprised me how quickly they finished that phase of the project.

I'm not a PTC/ACSES expert, but it seems archaic to be stringing fiber optic wire on poles - I would think that would make the system more vulnerable to branches falling onto the ROW, which seems to happen often on this line. Perhaps poles were chosen for lower cost or shorter installation time to meet the PTC deadline?

Too bad they couldn't have substituted galvanized steel poles, moved them closer to the tracks and strung up some catenary while nobody was looking...
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Re: Needham Line Questions / Discussion

Postby MBTA3247 » Mon Sep 11, 2017 11:39 am

NeedhamLine wrote:Too bad they couldn't have substituted galvanized steel poles, moved them closer to the tracks and strung up some catenary while nobody was looking...

That would have made too much sense. :P
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Re: Needham Line Questions / Discussion

Postby BandA » Mon Sep 11, 2017 4:16 pm

I thought the poles were for the wifi fiber, while the PTC fiber was being buried.
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Re: Needham Line Questions / Discussion

Postby NeedhamLine » Tue Sep 12, 2017 8:16 am

BandA wrote:I thought the poles were for the wifi fiber, while the PTC fiber was being buried.


That would make too much sense! According to this PTC summary http://www.mbta.com/uploadedfiles/About_the_T/Board_Meetings/PTC%20Update%206-26-17%20FOR%20POSTING.pdf the PTC installation will include 230 miles of new pole lines and 50 miles of upgraded existing pole lines.

So there may be some signal-related delays when trees/branches come down, but at least passengers will have speedy Wi-Fi to keep ourselves entertained while we wait.
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Re: Needham Line Questions / Discussion

Postby BostonUrbEx » Tue Sep 12, 2017 3:13 pm

NeedhamLine wrote:but at least passengers will have speedy Wi-Fi to keep ourselves entertained while we wait.


Not quite, seeing as the wifi plan is on the verge of being gutted by the general public.
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