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Re: Recent derailments - Metro North
Author: mook
Date: 12-06-2013 - 18:01
I mentioned regen because a presentation several years ago at a model railroad meeting (by somebody who should know) said that the CAF cars bought by Sac RT in the early 2000s have both regen and backup dynamics. Presumably (it wasn't described) they can switch between them, but RT supposedly locked out the regen because they don't have enough traffic to always have another train in the power block to absorb it. The CAFs seem to have fairly modest grids under the car someplace, so a heavy braking episode can result in interesting smells (NOT just hot brake shoes!).
Modern (since at least the 1980s anyway) LRVs seem to mostly have a disc brake mounted to the axle for friction braking.
Back to regen - RT's issue essentially is that the substations are all (given the 1980s and later construction) solid-state. Can't "run the meter backward." So what were they thinking? One thing perhaps is that on a couple of bridges voltage drop is common - substations a little distance away. There was supposed to be a project where some substations would get "supercapacitor" banks to store power from the cars going downhill to use for cars going uphill. Have never heard whether it got done - but we do still lose the lites and a/c occasionally over the bridges, and actually stalled once, so I suspect not.
The presenter when asked said that the old (mid-1980s, mostly) Siemens cars are dynamics (wasted through grids) only - and they don't get interesting smells after hard stops so apparently the grids are big enough. The CAFs do stop faster than the Siemens, though, when all the anchors are dropped.
In 10 years of riding SacRT I can't recall any significant problems due to overspeed (except for the occasional trip if a driver lets it get more than about 1 mph over the limit). Though it can be a pretty good crack-the-whip in the last car of a 4-car eastbound on one bridge (25 mph curves, but many drivers hit it hard as soon as the front end is on the straight).
Modern (since at least the 1980s anyway) LRVs seem to mostly have a disc brake mounted to the axle for friction braking.
Back to regen - RT's issue essentially is that the substations are all (given the 1980s and later construction) solid-state. Can't "run the meter backward." So what were they thinking? One thing perhaps is that on a couple of bridges voltage drop is common - substations a little distance away. There was supposed to be a project where some substations would get "supercapacitor" banks to store power from the cars going downhill to use for cars going uphill. Have never heard whether it got done - but we do still lose the lites and a/c occasionally over the bridges, and actually stalled once, so I suspect not.
The presenter when asked said that the old (mid-1980s, mostly) Siemens cars are dynamics (wasted through grids) only - and they don't get interesting smells after hard stops so apparently the grids are big enough. The CAFs do stop faster than the Siemens, though, when all the anchors are dropped.
In 10 years of riding SacRT I can't recall any significant problems due to overspeed (except for the occasional trip if a driver lets it get more than about 1 mph over the limit). Though it can be a pretty good crack-the-whip in the last car of a 4-car eastbound on one bridge (25 mph curves, but many drivers hit it hard as soon as the front end is on the straight).
