Got a swatch of a dead man’s switch?
Semper Vaporo I think that plaid speed has a checkered past.
I think that plaid speed has a checkered past.
Tweed speed?
Especially for 2nd Officer and Engineer Scott.
C&NW, CA&E, MILW, CGW and IC fan
schlimm Is plaid speed faster than warp speed, Captain?
Dave H. Painted side goes up. My website : wnbranch.com
Semper Vaporo
Pkgs.
gardendanceouter limits of ridiculousness, and at ludicrous, or maybe even, plaid, speed.
Is plaid speed faster than warp speed, Captain?
I guess it's not proper for me to complain about you guys not being on topic, since the title asks if locomotives can be too fast, and I have contributed my own small ridiculousness, but we are just about reaching the outer limits of ridiculousness, and at ludicrous, or maybe even, plaid, speed.
Patrick Boylan
Free yacht rides, 27' sailboat, zip code 19114 Delaware River, get great Delair bridge photos from the river. Send me a private message
Wizlish Now someone will probably dredge up the old physics textbook chestnut about how fast you have to accelerate the ACS-64 to blue-shift the red signal aspect to where it appears to be green. The correct answer: who cares; Amtrak uses position as well as color in the lights...
Now someone will probably dredge up the old physics textbook chestnut about how fast you have to accelerate the ACS-64 to blue-shift the red signal aspect to where it appears to be green. The correct answer: who cares; Amtrak uses position as well as color in the lights...
But is has applicability to all the new signals that are being installed everywhere but the NEC for PTC as they are all Color Light signals, not Position Light or Color Position Light.
However, with that shift, if all signal heads displayed Green, that would be a improperly displayed signal - as there is no Green over Green - only signals with a Single Head could be corrupted by the phase shift.
Never too old to have a happy childhood!
switch7frgGee , I guess the laws of physics and kinetics can't be violated, if they are , serious consequences happen even that electricity at 186.000 mph.This is what my 1936 physics book for dummys says
Electricity isn't the same thing as electromagnetic radiation. Only the latter propagates at 'lightspeed'. Actual motion of electrons -- which have mass -- is less than that (if I recall correctly, about .91c) and electrons in a wire can be much, much slower ... erikem will have the number at his fingertips, but I think drift speed of an electron in DC through copper wire can be very slow. Of course the effect is quicker than that, as popping an electron into one end of the wire will 'quickly' result in another one popping out at the other end, but again that doesn't happen with a timing corresponding to movement or propagation at c.
So not as much a topic for 'dummies' as might be thought...
.].BaltACD, I am embarrassed. Myfault, I hit the wrong key. I shall hide my head in shame.
Y6bs evergreen in my mind
It's not just a good idea, it's the law.
switch7frg Gee , I guess the laws of physics and kinetics can't be violated, if they are , serious consequences happen even that electricity at 186.000 mph.This is what my 1936 physics book for dummys says. But that was then , but this is now. switch7frg
Gee , I guess the laws of physics and kinetics can't be violated, if they are , serious consequences happen even that electricity at 186.000 mph.This is what my 1936 physics book for dummys says. But that was then , but this is now. switch7frg
When did electricity slow down to 186,000 MPH - I have always been taught it is at 186,000 MPSecond.
A good place to start is the Wikipedia page for PTC
Wiki PTC
There are two systems that meet the mandated PTC requirements offered in the US.
ACSES which is what Amtrak chose and subsequently so did Commuter Agencies that operate on the NEC.
The Class I freight railroads chose Wabtec's ETMS system; with BNSF choosing the "Cadillac" version V-ETMS and the other Class Is choosing the "Chevy" version, I-ETMS. The V-ETMS version has additional functionalities beyond what is required to meet the mandated PTC requirements and will be a "vital" system with dual on-board systems. Locomotives equipped with either version will be able to operate on a railroad that the lineside equipment and still meet PTC requirements.
Note that Amtrak and NS are discussing equipping a portion of the NEC with both ACSES for Amtrak trains and V-ETMS for NS trains so that NS will not need a dedicated fleet of locomotives for its trains that need to use the NEC in Maryland and Delaware. Presumeably the V-ETMS equipment would be at NS' expense.
gardendanceOne other old fashioned thought was that some of these control systems seem to give a warning first, and have a time lag before they actually impose the speed restriction, turn off the acceleration and apply the brakes. I hope a sensible system would not just give a warning if the train was speeding.
Other critical concept. Railroad signal systems are not about the last signal, they are about the next signal, about what's coming up. So in a sense all signals warn about a restriction, but don't take action until the restriction is exceeded. The whole point of a block signal system is to give you warning.
An approach signal isn't a signal to stop. Its a signal that tells you at the next signal you may have to stop. Depending on the system you would have to acknowledge the restrictive indication, but you don't have to stop until the next signal and under existing cab signal systems, it won't penalize the train until the train passes the red signal without stopping. In most cab signal systems it doesn't impose a "speed restriction", it stops the train. If you do not comply the train stops.
Thanks to all of you who have mentioned that sensible control systems would tell the train what the safe speed is, and the train would know not to exceed the speed. My dinosaur brain was thinking of wayside signals, or even cab signals which I believe are just wayside devices whose aspects display in the cab.
One other old fashioned thought was that some of these control systems seem to give a warning first, and have a time lag before they actually impose the speed restriction, turn off the acceleration and apply the brakes. I hope a sensible system would not just give a warning if the train was speeding.
Also remember that not all cab signal systems have speed enforcement for each restrictive aspect. Those that don't would allow a train or engine to go by a red signal at track speed as long as the engineer pressed the acknowledgement button each time the cab signal changed to the next more restrictive aspect.
Jeff
And this assumes that there is, indeed, some form of cab signalling extant. Not all lines with signals have cab signals.
On lines without cab signalling (or any relative thereof), the speed of the train is controlled solely by the engineer. If he/she wants to blow by a "clear" signal at 80 in 40 MPH territory, well.....
The closest thing to external speed enforcement on such signalled lines and in dark territory (other than weed weasels) is a defect detector that reports speed, or a train report clear of a given point much sooner than they perhaps should have.
And we can't forget the event recorder, which tells all.
Larry Resident Microferroequinologist (at least at my house) Everyone goes home; Safety begins with you My Opinion. Standard Disclaimers Apply. No Expiration Date Come ride the rails with me! There's one thing about humility - the moment you think you've got it, you've lost it...
[quote user="gardendance"]You guys seem to know much more about all sorts of signal systems, but nobody's clearly answered what I apparently haven't phrased properly: can a train pass a place where the signal system checks its speed, going under the speed limit, and accelerate so quickly that it's dangerously over the speed limit before it gets to the next place where the system checks its speed?
I don't know whether you have been satisfied with the answers but it is my belief that the answer to your question is No. As has been stated, the signal system does not check the trains speed, it indicates the maximum allowed speed to the train. The train compares its speed and if that speed is exceeded, acts to get the speed reduced. The trains power is not a factor since the power can be reduced by the trains controls. However, in the Philadelphia accident, the signal system did not have track speed limitations in its capabilities so the signal system only was giving the train a clear signal that allowed it to go at whatever speed the engineer set. Thus the train was free to accelerate and therefore did not prevent the accident. PTC does include track speed information and could have prevented the accident.
As to whether the train could be powerful enough to overspeed, that is also a No because if the train has received the signal to not exceed XX mph, as soon as the train accelerated to that speed, the control system on the train would operate to reduce the speed.
dehusman The engine reads the signal indication and then looks at how fast its going. If its too fast for the indication then the engine applies the brakes.
This, of course, is one of the major differences with PTC.
Euclid Patrick, I don’t know how those systems work, but I understand your question. Basically, it seems to me that the external system would have to impose the speed limit for the track, and an internal system on the locomotive would have to continuously monitor speed and prevent it from exceeding the externally imposed limit.
With existing speed control (Cab signal based), braking curves are baked into the locomotive born device based on "worst case".
With PTC, the location along the track is a combo of GPS and dead reckoning. Which track is sent from dispatch system to train. Allowable track speed (civil limit) is in database on locomotive's PTC computer and is downloaded before the trip.
-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/)
gardendance .... can a train pass a place where the signal system checks its speed, going under the speed limit, and accelerate so quickly that it's dangerously over the speed limit before it gets to the next place where the system checks its speed?
.... can a train pass a place where the signal system checks its speed, going under the speed limit, and accelerate so quickly that it's dangerously over the speed limit before it gets to the next place where the system checks its speed?
No. But only because that's not how the systems work. The signal system doesn't check the speed. The signal system tells the train what the signal indication is. The engine reads the signal indication and then looks at how fast its going. If its too fast for the indication then the engine applies the brakes.
Most of your replies mention what you think the signal system will do once it finds out the train's speeding, but don't mention how often the signal system checks speed,
With any of the cab signal systems the speed control is based off the ENGINE. The external signal system doesn't measure the speed per se. Al the systems, including PTC feed the signal indications (or speed restrictions in the case of PTC) to the engine and the ENGINE determines whether the speed is being exceeded. Having the system external to the engine try and figure out the speed would be unsafe because of the possibility of communication failure.
If I remember correctly, Amtrak has an internet system that tells everyone train speed, but no mention of how often it checks speed, and apparently that system has nothing to do with controlling speed.
None of the external (to the engine) signal systems control the speed. They communicate the required speed tothe engine and the engine figures out whether its speeding.
Present-day systems determine the speed of the locomotive solely from on-board equipment (typically a mini-generator on one of the axle, or a speed sensor that is also part of the anti-slip / creep control feature, etc.).
Speed is not determined by wayside equipment such as radar, or a timer/ 'trap' setup that clocks how long the train takes to go a set measured distance, etc. The only examples of those that I know of are the ones that the Southern Rwy. used on the Saluda grade to determine whether the train was under control and going slow enough to continue down the grade, or was going too fast and needed to be switched into the safety track to get stopped before it went any farther.
- Paul North.
gardendance You guys are giving me much edutainment and entercation about different kinds of signals, but not much info about if the locomotive can be so powerful that the system can't react quickly enough. Some of you have even suggested that I think the signal system would tell the locomotive to put on the brakes, but wouldn't be smart enough to tell it to turn off the acceleration, and this makes me sad. Won't someone turn my frown upside down? You guys seem to know much more about all sorts of signal systems, but nobody's clearly answered what I apparently haven't phrased properly: can a train pass a place where the signal system checks its speed, going under the speed limit, and accelerate so quickly that it's dangerously over the speed limit before it gets to the next place where the system checks its speed? Most of your replies mention what you think the signal system will do once it finds out the train's speeding, but don't mention how often the signal system checks speed, although dehusman mentions one system that RECORDS the speed every 15 minutes. If I remember correctly, Amtrak has an internet system that tells everyone train speed, but no mention of how often it checks speed, and apparently that system has nothing to do with controlling speed.
You guys are giving me much edutainment and entercation about different kinds of signals, but not much info about if the locomotive can be so powerful that the system can't react quickly enough. Some of you have even suggested that I think the signal system would tell the locomotive to put on the brakes, but wouldn't be smart enough to tell it to turn off the acceleration, and this makes me sad. Won't someone turn my frown upside down?
You guys seem to know much more about all sorts of signal systems, but nobody's clearly answered what I apparently haven't phrased properly: can a train pass a place where the signal system checks its speed, going under the speed limit, and accelerate so quickly that it's dangerously over the speed limit before it gets to the next place where the system checks its speed?
Most of your replies mention what you think the signal system will do once it finds out the train's speeding, but don't mention how often the signal system checks speed, although dehusman mentions one system that RECORDS the speed every 15 minutes. If I remember correctly, Amtrak has an internet system that tells everyone train speed, but no mention of how often it checks speed, and apparently that system has nothing to do with controlling speed.
Automatic Train Control is a continuous system. As soon as speed gets over the specific setting, it gives an audible warning for a few seconds (ours is 6 seconds) before taking the air.
In those few seconds you either have to get back under speed or go to suppression on the automatic brake.
BaltACD dehusman Cab signals are for track occupancy and routing. They do not reflect temporary or permanent speed restrictions. Train ahead. Restrictive signal. Switch lined other than normal. Restrictive signal. Track clear and switches lined normal. Clear signal. Cab signals, as they exist today, and PTC are totally different.
dehusman Cab signals are for track occupancy and routing. They do not reflect temporary or permanent speed restrictions. Train ahead. Restrictive signal. Switch lined other than normal. Restrictive signal. Track clear and switches lined normal. Clear signal.
Cab signals are for track occupancy and routing. They do not reflect temporary or permanent speed restrictions.
Train ahead. Restrictive signal.
Switch lined other than normal. Restrictive signal.
Track clear and switches lined normal. Clear signal.
Cab signals, as they exist today, and PTC are totally different.
Cab Signal with speed enforcement gets close to some aspects of PTC, requiring braking (suppression style) or slowing (LSL) to adhere with speed associated with the signal aspect.
Suppression style required a 17# reduction when a more restrictive aspect was encountered and the current speed was over the speed for that aspect (e.g. you are running 60 mph on a clear and you get an approach medium (45mph) in the cab)
LSL required that you slow down to the speed associated with the next lower aspect's speed along a pre-programmed braking curve. (e.g. you are running 50 mph on a clear and get an approach medium. You have to slow down to 30 mph. You then get a restricting, you have to slow down to 20 mph.)
gardendance Can locomotives be so peppy that any overspeed controls would render them useless? This is kind of related to the Amtrak 188 wreck at Frankford Junction Philly. If I remember correctly the train didn't start speeding until near the end of 80mph territory going into 50mph territory and finished at over 100mph. It also seems to me that it traveled a relatively short distance to accelerate those 20 or so mph, when it should have decelerated about 30 or so mph. I've also read some posts that said although Frankford Junction curve's speed limit is 50mph that it's possible to traverse it at 80mph without derailing. Is the ACS64 so poweful that it could have accelerated from 50 to 80+mph so fast that an overspeed control would not have slowed it in time? Of course I may be way off on my numbers in this case, but in any case it seems to me that it's possible to have a locomotive whose accelration is so good, and some speed limits so restrictive, that no overspeed control would be worthwhile. Also of course there are some whose opinion is that Positive Train Control's cost-benefit ratio makes it not worthwhile either.
Can locomotives be so peppy that any overspeed controls would render them useless?
This is kind of related to the Amtrak 188 wreck at Frankford Junction Philly. If I remember correctly the train didn't start speeding until near the end of 80mph territory going into 50mph territory and finished at over 100mph. It also seems to me that it traveled a relatively short distance to accelerate those 20 or so mph, when it should have decelerated about 30 or so mph.
I've also read some posts that said although Frankford Junction curve's speed limit is 50mph that it's possible to traverse it at 80mph without derailing.
Is the ACS64 so poweful that it could have accelerated from 50 to 80+mph so fast that an overspeed control would not have slowed it in time?
Of course I may be way off on my numbers in this case, but in any case it seems to me that it's possible to have a locomotive whose accelration is so good, and some speed limits so restrictive, that no overspeed control would be worthwhile. Also of course there are some whose opinion is that Positive Train Control's cost-benefit ratio makes it not worthwhile either.
No. PTC is predictive, not reactive. It would enforce the braking curve needed to get the train down to speed in time for the curve. It wouldn't matter how powerful the locomotive is. It just has to know about train braking capability
My experience in riding the front platform of LIRR and PRR MP-54's (first time at age 8, summer 1940, returning from the Worlds Fare, last time 1992, going to a job inspection at Princeton U.) is that the PRR cab-signal system DID, at least at one time, include speed control for permanent speed restrictions, or at least some permanent speed restrictions. The horn would blow, and the engineer would have to acknowledge.
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