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  • Type 7 Overhaul Program

  • 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: sery2831, CRail

 #437570  by StevieC48
 
I dont want this to go OT: But eventualy DC transit motors will be obsolute. There is rumors the other major rebuild is looking to change propulsion system to A/C.

 #437623  by F-line to Dudley via Park
 
Some years after the car fleet goes fully AC (including work cars), would they ever consider converting the overhead from DC to AC to simplify and eliminate the need for converters...or are there technical reasons why the power source should remain the same as ever? I guess ditto for the heavy-rail lines since those fleets will probably be 100% AC in about 20 years.

 #437679  by tommyboy6181
 
The overhead would more than likely not change. Knowing a little about electrical and also having looked at other forums, if you were to switch to AC, it would create a ton of sparking since the current will not travel as well over long distances. All new systems from ground up even since 2000 will use DC for the overhead/third rail due to that reason. Therefore, the overhead more than likely will remain DC but use AC propulsion with inverters to make it all work.

 #438539  by MBTA3247
 
tommyboy6181 wrote:The overhead would more than likely not change. Knowing a little about electrical and also having looked at other forums, if you were to switch to AC, it would create a ton of sparking since the current will not travel as well over long distances. All new systems from ground up even since 2000 will use DC for the overhead/third rail due to that reason. Therefore, the overhead more than likely will remain DC but use AC propulsion with inverters to make it all work.
Huh? AC travels much better over long distances than DC does, wth a lot less power lost to resistance in the wire. As for sparking, DC seems to do just fine in that department :wink:

Actually, I think the main reason for not switching over to AC is that you'd have to add a rectifier to each car to provide direct current to the inverter.

 #440160  by orange1234
 
3678 has been repainted and is in service according to NETransit.

 #440373  by -Garrett
 
I can't remember if anyone mentioned this, but do the Rehabed Type 7's look any different on the inside as well? Are they applying the same new seat padding and hand grabbers as in the other lines?

 #440375  by onthegreenline
 
I rode 3667 Wednesday and was surprised - it doesn't even look like someone bothered to take a bottle of windex and clean the grime off the inside. Nothing's changed at all on the inside...

 #440417  by sery2831
 
Well we dont know what they are going to do in this rebuild yet. The two cars that have been painted have not gone through the rebuild program. That program is to start sometime next year.

 #441041  by F-line to Dudley via Park
 
-Garrett wrote:I can't remember if anyone mentioned this, but do the Rehabed Type 7's look any different on the inside as well? Are they applying the same new seat padding and hand grabbers as in the other lines?
Except for the interior LED screens for the ASA system the Type 7's modded to trainline with Type 8's are no different on the inside. But then again those had no modifications done except for the ASA and trainline electronics because the rest is being done in the rehab program next year. No details yet released on what will be changed except for the exterior body work to fix the dings and rust, and the new paint job. I would think the seats would probably be re-padded since they're still the original 1986 fabric and that you'd get the hand straps the heavy-rail cars are getting. Probably also will get the fiberglass Green Line maps over the doors replaced since they're all falling off and the eliminated B-line stops are covered in white-out. Unfortunately also means the 1986 system maps that are in the ad frames behind the operator cabin will probably be replaced...if you peek behind the ad you'll still see the Washington St. El stops!

Don't know what else may get changed. There's been rumors that they'll get AC propulsion, meaning they'd take on the trademark whine of the Type 8's. Probably will also see the exterior brake lights. door lights, and in-service lights replaced with LED's so they're brighter and they don't have to change bulbs anymore (they did that on all the rehabbed RTS buses so natural to do it here), and would probably make sense to add the turn signals that the Type 8's have since they're needed on the E at Huntington-South Huntington and South Huntington-Heath loop, the B at Packard's Corner and Lake St./BC, and yard moves at Cleveland Circle/Reservoir carhouse and Chestnut Hill Ave. And of course it would be great (if wishful thinking) to replace those awful, awful unreadable LCD destination signs with those bright and razor-sharp LED ones all the buses now have.

 #452610  by mattster
 
Saw 3678 the other day and got a short video on my cell phone. 3667 already has a huge gash in the paint on one side.

 #453091  by Ricky Smith
 
Someone had mentioned the reason they haven't gone to AC for the power lines is because of something to do with how the signaling system works.

 #453253  by mikeinboston
 
I suppose the Green Line could theoretically be converted to AC should the T see significant value in doing so. There would need to be some extensive updating of equipment.

The heavy-rail lines would be more difficult to convert (potentially impossible), as AC is generally practical only when used on overhead catenary. Third rail cannot carry as much current when powered with AC, and it can't operate at high voltages (above ~1000V), which would mean reduced capacity and possibly less frequent train headways.

Either would be a major undertaking, and with the T's current debt and deferred maintenence load, I can't see either happening anytime soon.

 #453587  by sery2831
 
Lets keep this thread on the over haul program. The system is keeping DC overhead power while cars may be converted to AC motors. If we want to discuss the overhead or signals on the Green Line, lets use this thread:

http://www.railroad.net/forums/viewtopic.php?t=44089

Thanks

 #454084  by StevieC48
 
from what I'm told the Type 7's will not be getting a/c propulsions, the inverters that they were looking for bids for were for the a/c plugs and some circuitry on the car.

 #454217  by Guilford Guy
 
I saw 3678 today.
I put a dollar on 3663 getting painted next. Its nice to finally see some T logos on equipment again. 3663(old green, white, and black) has a T logo where the green paint has come off...
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