Needham Line Questions / Discussion

[RenegadeMonster]

What does the shunt do? Show the track as occupied?

[Backshophoss]

The Shunt completes the circuit that shows the track is occupied.

[BandA]

It simulates the steel wheel/axle of the train. Do they double check it with an ohmmeter?

[Disney Guy]

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.

[BandA]

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

[Trinnau]

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

They verify proper shunt with the dispatcher.

[Stephen]

Do they double check it with an ohmmeter?

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

(Sorry, had to...)

[johnpbarlow]

No Saturday service today on Needham line due to PTC installation per status sign at Needham Heights.

[johnpbarlow]

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?

[BostonUrbEx]

The poles are to hang up the fiber optic communications cable on.

[NeedhamLine]

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...

[MBTA3247]

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.

[BandA]

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

[NeedhamLine]

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.

[BostonUrbEx]

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.