HarveyK400As for the PRR, the reason the continuous 100-Hz traction frequency was not "picked up" was that code bursts at 75, 120, and 180 cps were transmitted, activating the respective tuned vane relay in the locomotive/emu receiver unit for 30, 45, & up to 125 mph commands.
-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/)
Wow. We need to go to wireless wayside signalling. I'm just too engrossed with this 19th century block signalling stuff.
Yeah I sorta meant that "not using the rails" part.
I need to read up what all those boxes are between the rails are for. I'm not sure even Metro knows what they're for.
Did the NTSB made the final statement? Does Metro gets any stimulus money to fix their problems?
NTSB released the track to WMATA about a month ago.
There has not yet been a "ruling" from them.
WMATA is doing extensive track work all summer. Every day has several alerts posted for delays due to track work. It was not this busy before the accident, but the accident's time does coincide with the release of a substantial amount money to perform maintenance on the entire system, anyway.
aegrotatioI need to read up what all those boxes are between the rails are for. I'm not sure even Metro knows what they're for.
A lot of them are impedence bonds that allow the traction return current to flow between signal blocks. You can read about them here: http://www.twincomfg.com/Impedance_Bonds/Twinco_ImpedanceBonds.htm
Oh! Okay, where are the sensors? Oh, wait, they are using track circuits.
Now we find out there was a smilar incident where a 2nd train almost ran into a first and a third train almost ran into the second. Shouldn't that have raised a red flag in 2005????
From my point of view we have a system that works almost perfectly and about once every couple of years there is a failure. Trouble is that this year it resulted in fatalities.
Adding to the misery, this morning (Sunday) a purple-purple, WMATA code for a person struck by a train, at the Gallery Place metro station on the Red Line. It was a suicide by train and confirmed that the individual intentionally jumped from the platform. Sigh. The station was re-opened within four hours.
It's a really bad year for WMATA.
HarveyK400 oltmannd HarveyK400These factors may be exacerbated by the unusually long, 1,700-ft blocks for this type of signaling. PRR coded track circuits/cab signal blocks were typically 2 miles long but generally were split into two track circuit "cut sections". 1700 feet would be a very short track circuit in the PRR world. Still think it highly unlikely that leakage could have enough oomph to get over the on-board amplifier sensitivity. The SD60MAC demo units running at 70 mph were feeding 100Hz power to the traction motors, but even with the cables only a few feet away from the cab signal receiver bars, there wasn't enough signal to get the 100Hz cab signal system to pick up. First, one comment was that most Metro blocks were 400-1,000 feet long. Another writer mentioned a nominal 1,500-foot limit. I recall the latter figure for the CTA's original cab signal system as well. When it was quiet, you could hear the code pinging along the Lake-Dan Ryan and Jefferson Park extension. As for the PRR, the reason the continuous 100-Hz traction frequency was not "picked up" was that code bursts at 75, 120, and 180 cps were transmitted, activating the respective tuned vane relay in the locomotive/emu receiver unit for 30, 45, & up to 125 mph commands. As you pointed out, blocks could be up to two miles long; but also lengthened by cut sections amplifying and repeating the weakened block circuit signal.
oltmannd HarveyK400These factors may be exacerbated by the unusually long, 1,700-ft blocks for this type of signaling. PRR coded track circuits/cab signal blocks were typically 2 miles long but generally were split into two track circuit "cut sections". 1700 feet would be a very short track circuit in the PRR world. Still think it highly unlikely that leakage could have enough oomph to get over the on-board amplifier sensitivity. The SD60MAC demo units running at 70 mph were feeding 100Hz power to the traction motors, but even with the cables only a few feet away from the cab signal receiver bars, there wasn't enough signal to get the 100Hz cab signal system to pick up.
HarveyK400These factors may be exacerbated by the unusually long, 1,700-ft blocks for this type of signaling.
PRR coded track circuits/cab signal blocks were typically 2 miles long but generally were split into two track circuit "cut sections". 1700 feet would be a very short track circuit in the PRR world.
Still think it highly unlikely that leakage could have enough oomph to get over the on-board amplifier sensitivity. The SD60MAC demo units running at 70 mph were feeding 100Hz power to the traction motors, but even with the cables only a few feet away from the cab signal receiver bars, there wasn't enough signal to get the 100Hz cab signal system to pick up.
First, one comment was that most Metro blocks were 400-1,000 feet long. Another writer mentioned a nominal 1,500-foot limit. I recall the latter figure for the CTA's original cab signal system as well. When it was quiet, you could hear the code pinging along the Lake-Dan Ryan and Jefferson Park extension.
As for the PRR, the reason the continuous 100-Hz traction frequency was not "picked up" was that code bursts at 75, 120, and 180 cps were transmitted, activating the respective tuned vane relay in the locomotive/emu receiver unit for 30, 45, & up to 125 mph commands. As you pointed out, blocks could be up to two miles long; but also lengthened by cut sections amplifying and repeating the weakened block circuit signal.
it sad to know the problem was bigger than anticipated.
Another couple of fatalities, but these were purple-purple (people jumping in front of trains).
2009 is a really, really dark year for WMATA.
I hope the NTSB finds out something on the crash. There is no real data yet, which is frightening, and the moving of 1000-series cars to the middle of the trains was a Public Relations stunt and the Washington Post is arguing with WMATA about that fact.
It is a very dark year for the premier subway in America. I don't think the emperor has no clothes, but a simple wayside sensor failure is being interpreted as a huge systemic failure and I think that is just not correct.
New video produced by the DCFD includes interviews and never-before-seen photographs and video.
http://www.youtube.com/watch?v=Eds6yEgL_Ng
It was reported last week that WMATA has been replacing parts of the Alstom system with incompatible parts from Union Switch & Signal. Furthermore, the failure of these incorrect parts is not noticed by the system.
The section of track where the crash occurred, killing nine and injuring more than twenty more, had its Alstom signalling equipment replaced with incompatible US&S equipment just five days earlier. Technicians and track workers expressed worries about incompatible equipment and were rebuffed.
More: http://spectrum.ieee.org/riskfactor/computing/it/dc-metro-crash-caused-by-incompatible-equipment
And more, with transcripts from NTSB discovery: http://voices.washingtonpost.com/getthere/2010/02/_family_members_of_victims.html
And still more: http://www.washingtonpost.com/wp-dyn/content/article/2010/02/24/AR2010022403006.html
Quoting from Tiffner's testimony. My commentary would be redundant:
"You know that these bonds -- you're using two different manufacturers. You're using something 40 years old and you're putting something brand new. The impedance of these newer bonds do not match the impedance of these older things. So in the process, they have to bump that power up to get more signal out there in order for the bond -- the circuit to operate properly. We've complained about this and complained about this."
and another thoughtful quote:
"These circuits are doing something very funny. There's no reason why you put a 10 foot soft shunt at the transmitter, why the heck that transmitter will not -- that circuit will not go down when you got a shunt all the way down there. That problem we had at signal 2, how the heck can you have a train with all them axles sitting five feet from a bond and that circuit stay up? And they came after the same night and put original bond back in there and it worked fine. You tell me how that happens. There's something flakey about that, some kind of resonate harmonic, some kind of cross-talk. You're bumping that power way up, I assume, and it's getting cross-channel talk. I don't know. I'm not -- I worked at Westinghouse for the F16 radar for the B1B bomber. I've seen a lot of strange things in my time, but there it's even more advanced systems than what this stuff is. But for a relatively simple type of circuit, how this could happen, it -- I don't understand it, you know. But it's a strange occurrence that's happening with these circuits, so it's logical to think that these do not belong together."
http://www.wtop.com/?sid=1702179&nid=25
Click the above link and see on the left side Photo Gallery of the accident.
It does not matter what the operator was doing in this accident!!
The trains run themselves. The operator just closes the doors and intervenes when anomalies happen.
Evidence has shown that the operator in the nine-fatality accident did, indeed, activate the emergency brake. The rails show evidence of this happening (blue coloring).
DMUinCTElectronics, The late 1940s, the Transistor is invented, the radio tube is doomed. Late 1950s TI comes up with the Intergrated Circuit Chip. The 1970s, the Micro-Processor, a full computer on one chip, starts to find uses. By 1974 PC Boards made up of IC Chips for switching with Transistors or SCR for input/output drivers. How long the board will last was not known, even if Military Spec.tested components that will work at high and low temperatures.In 1981, IBM introduces the Personal Computer, the PC. By the mid-1990s most boards still work, but for those that fail, repair parts are unavailable. Been their, done that. Replacement PC Boards to cover maintenance contracts must be designed to do the same job but with new components. The mix of old and new PC boards MUST work together. Do you have a 35 year old TV set ? Will it still work ? Maybe, maybe not.
Electronics,
The late 1940s, the Transistor is invented, the radio tube is doomed.
Late 1950s TI comes up with the Intergrated Circuit Chip.
The 1970s, the Micro-Processor, a full computer on one chip, starts to find uses.
By 1974 PC Boards made up of IC Chips for switching with Transistors or SCR for input/output drivers. How long the board will last was not known, even if Military Spec.tested components that will work at high and low temperatures.
In 1981, IBM introduces the Personal Computer, the PC.
By the mid-1990s most boards still work, but for those that fail, repair parts are unavailable. Been their, done that. Replacement PC Boards to cover maintenance contracts must be designed to do the same job but with new components. The mix of old and new PC boards MUST work together.
Do you have a 35 year old TV set ? Will it still work ? Maybe, maybe not.
The thing about transistors and SCR's is that they are still available, and if you are minimally competent technician & minimally competent with a soldiering iron these kind of boards can be repaired.
Most relay logic circuits are simple enough a good plumber can follow them.(This is what I learned working on a Surface to Air missile system(Nike Hercules)
For those of you who are older MR's remember the Twin T circuit?
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