• Red-Blue Connector

  • Discussion relating to commuter rail, light rail, and subway operations of the MBTA.
Discussion relating to commuter rail, light rail, and subway operations of the MBTA.

Moderators: CRail, sery2831

  by ceo
 
My understanding is that because Cambridge St. was roughly doubled in width in the 60s, all the utilities are on one side and the other side is relatively clear underneath.
  by Charliemta
 
ceo wrote: Wed Apr 28, 2021 7:41 pm My understanding is that because Cambridge St. was roughly doubled in width in the 60s, all the utilities are on one side and the other side is relatively clear underneath.
Cambridge Street was widened to its current width in the 1920s. There were small adjustments done to the width in the 60's when the West End was demolished and replaced with Charles River Park, but that was pretty minor.
  by MattW
 
CRail wrote: Wed Apr 28, 2021 6:59 am
BandA wrote: Mon Apr 26, 2021 2:16 pm Are any tests required when reversing ends on stub-ended stations like this one? Like the brake tests required of the Commuter Rail equipment by the FRA?
Subway equipment is straight air, not train air. You also need a 2 person crew to do a terminal brake test, which takes about 6 seconds to do so it otherwise wouldn’t matter.
This is a little off topic, but what is meant by straight air as opposed to train air?
  by Disney Guy
 
Electrical lines can be rerouted in a manner that when stringing the new wires or decommissioning the old wires no sparks jump and no homes or businesses lose power. Sewer lines are more complicated because the new line must have the same downslope from the construction project starting point to the project ending point or alternatively a pumping station requiring the grinding of semisolid material and requiring electricity installed somewhere in the middle.

OT: Straight air. A "brake pipe" (with hoses between cars) runs the full length of the train. When the engineer or motorman applies the brakes, air from the reservoir (air tank) in the engine goes down the brake pipe and into the brake cylinders of all the wheels of all the cars to stop the train. When the engineer releases the brakes, all the air is regurgitated back into the engine to be released at the brake valve under the engineer's hand or foot and the various brake shoes or pads in the various cars are released.

Train air. There is still the brake pipe going the full length of the train but each car has its own pressurized reservoir. When the engineer releases the brakes the brake pipe is depressurized. A mechanism* senses this loss of pressure and opens valve(s) that admit air from each respective car's reservoir to the brake cylinders to stop the train. When the engineer releases the brakes the brake pipe is repressurized by the engine's reservoir (and if applicable the compressor) . The sensors in the cars close off the brake cylinders from the reservoirs, vent the brake cylinders to the outside to release the brake shoes or pads, and also take the air pressure from the brake pipe to repressurize the reservoirs in the various cars.

As far as I know, the various brake tests before departure were selected and passed into law or written into operating handbooks based on the characteristics of the braking system but are selected administratively by each railroad. At Seashore Trolley Museum , when a car or train departs either endpoint, a brake application is done with the car in motion and ideally sufficiently so the motorman can verify that the brakes began to take hold but also light enough that there is not an obtrusive jolt.

* May be in the form of a multipurpose valve called a triple valve that "reconfigures" the air paths to admit or close off air flow between the brake pipe and the reservoir, between the reservoir and the brake cylinders, etc. It is possible for cars to have their own air compressors notably if they are passenger cars with their own electrical systems for lights, etc.
  by CRail
 
MattW wrote: Thu Apr 29, 2021 9:27 pmThis is a little off topic, but what is meant by straight air as opposed to train air?
Straight air is as Alan described it above. Charge the system and the brakes apply, drain the system and they release. The "brake pipe" in subway cars solely serves to hold closed an emergency valve (so that a train parting will drain the pipe and cause an emergency application) as each car (or pair of cars) supply their own source of air. With train air, the brake pipe pressure, fed from the engineer's brake valve, operates a triple valve in each car. Air via the brake pipe charges each car's reservoir until the reservoir pressure meets the pressure of the brake pipe, centering the triple valve. A reduction in brake pipe pressure causes the triple valve to allow air from the reservoir into the brake cylinders applying the brakes, the more the reduction, the more air is allowed into the cylinders. Returning air into the brake pipe sends the triple valve back into release kicking off the brakes and recharging the reservoirs. Train air can be difficult to wrap your head around, but once you do it all makes sense, it's pretty ingenious.

The point, though, is that subway equipment has a much simpler brake system. Each car controls its own brakes so there's no reason to test the integrity and continuity of the brake pipe since, if it were to fail, the system would remain 'dumped out' (in emergency). Another point is that, with subway equipment, the train must be dumped (put in emergency) to cut out the controller stand and change ends. This is not the case with train air.
  by Disney Guy
 
Even in this set of plans, the Mass. General Hospital portion would be an entrance only, not a link.

A suitable handicapped accessible path wholly within fare paid territory and connecting the Red Line and Blue Line platforms does not intersect any MGH owned property.
  by BandA
 
Some of the presentation slides are redacted due to security concerns?

I doubt that MGH is going to pay much towards this project.

Is there a new price tag?
  by Adams_Umass_Boston
 
In case people want to read the previous documents on the Red-Blue connector, I have been archiving them here which includes the 1986 proposal -
https://archive.org/details/@brianfrenc ... sort=-date
Last edited by Adams_Umass_Boston on Mon Dec 06, 2021 9:12 pm, edited 1 time in total.
  by TurningOfTheWheel
 
Great news to see it elevated to the active projects page.

A brief summary of the design report and chosen alternatives:
  • Construction expected to begin in 2025, project completion by 2030
  • Single, 320-ft island platform to the east of current Charles/MGH station
  • Entrances at current station headhouse and inside new MGH building
  • Retirement of Bowdoin station (Bowdoin loop may be converted to storage)
  • Tunnel will be dug using cut-and-cover and will be two+ tracks for its entire length (>2 only if storage tracks are placed east of Charles/MGH next to main running tracks)
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