Casselton Oil Train Wreck

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Posted by RME on Friday, March 17, 2017 12:39 PM

Murphy Siding
If I understand your explanation correctly, the sensor would be tripped when a truck pitches too far to the left or right, presumably predicting that it had gone too far out of the norm and a derailment was imminent?

I don't have links to the Spanish system or its patents handy, but it was discussed in at least one of the Creeping Lovecraftian Horror threads.  It is not the pitch of the truck that is detected, it is the yaw about the center pin, and in the Spanish system the "detection" is nothing more than an emergency trip when the truck yaws past the angle that represents the effect of the sharpest curve on the route.

A more sophisticated 'detection' would take account of the damped yaw rate as well as the absolute angle, since no intended curving would generate fast yaw, and any acceptable sideframe play or other cause of excessive uncontrolled bolster yaw would not have substantial magnitude.

Would the system then initiate an emergancy brake application on its own, or would it just alert the engineer of a problem?

The Spanish system is very simple, just a trip and a mechanical valve.  A system that 'warned the engineer' would require all sorts of additional complication -- a separate tone in the radio, some means of identifying where in the train the incident occurred, there are many possibilities that I don't want to encourage a detailed discussion of -- and their discussion noted that if the truck has rotated to the angle it trips the valve, it's appropriate to stop the train in minimum time anyway.  I would like to hear from buslist and others if this is indeed the 'best' appropriate strategy, given the expected propagation in the train.

How far would you think a truck would have to be off-kilter before the alarm went off? I've seen a train of empty rock gondolas on a bad track doing pretty spooky looking things. The cars appeared to tip left then right about 12" off vertical in quick succession, at about 10 mph. Would something like that tend to set off the alarm?

No.  Only actual yaw sufficient to trip the valve would set the 'alarm', and it would do it by triggering a big-hole reduction propagating from the valve location down the trainline in both directions.

I assume you have seen the Government video on 'how to derail a train'.  Three-piece trucks are extremely flexible in pitch, and can tolerate amazing amounts of 'twist' well past the point that the blocks above the roller-bearing housings are tipped in the sideframes without derailing.  There is no particular reason to use sideframe pitch alone as a derailment indicator (unless so paranoid about safety that you'd plug it at every tree).

Likewise, harmonic rock should not be used to trigger a mechanical valve, although it might be highly useful to warn an engineer when movement has built up to the degree you indicate -- I'd think 5 degrees of repeated magnitude would be alarming, let alone 12, but I'd defer to professional rails on just how much rock constitutes a need for warning.

Yes, I'd put some kind of small whistle on any mechanical 'derailment detector' valve to make it easy to find the 'anomalous car' at zero-dark and wet-thirty.  Perhaps cheap battery-powered lights near the sill, too.

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Posted by RME on Friday, March 17, 2017 12:52 PM

Erik -- sorry, I have no idea why I thought that was you.  I have edited the post accordingly.  (I did think it was a bit strange you'd say manual monitoring would be necessary...)

I've also heard enough over the years about industrial wireless sensors and various forms of energy harvesting to think that there are a fair number of non-video means of instrumenting a truck. Accelerometers and MEMS gyros can be quite cheap as long as you don't need INS accuracy.

Here the cell-phone craze has worked to significant advantage: very, very cheap accelerometer cores that 'double' as clinometers are available for a few cents apiece, with well-documentable accuracy and relatively easily implementable precision.  Much of the other hardware needed for a good standalone, low-maintenance solution comes from similar sources.

I would suspect that the easiest way to harvest energy would be from vibration and a small low-cost capacitor could store enough energy to get a useful signal out.

That is right.  Note however that there's more than enough vibration to charge even substantial batteries in a short time.

You could back up with solar power, as earlier indicated, as a backup to mechanical charging when the car sits for an extended period.  There are similar objections to those used for optical derailment detection; hardening the panels in a typical railroad environment can be difficult; it is easy for thieves to divert the panels to other uses.

Note that there are a number of ways that active charging, for example via induction, could be implemented.  This includes charging during the physical 'walk of the train' during inspections.

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Posted by Murphy Siding on Friday, March 17, 2017 2:15 PM

RME- Thanks for the explanation. Once you mentioned the yaw of the trucks, it clicked in my head and  understood it.

Thanks to Chris / CopCarSS for my avatar.

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Posted by Euclid on Friday, March 17, 2017 2:28 PM

Here is a mechanical-pneumatic derailment detector that dumps the air when it senses the physical forces that a derailment imposes on a railcar:



Here is the derailment detector used in Spain.  What provides derailment detection with this device is the mechanical disruption of the proximity of the truck and carbody relationship.  This is clearly shown in detail about 2/3 through the video or so. 

When a wheel leaves the rail, it abruptly drops down the height of the rail, and lands on the ties.  Since the carbody is riding on the other three axles, it remains relatively stable compared to the derailed wheelset.  So there is an unusually large movement with the truck frame with the derailed wheelset compared to the carbody. 

The derailment sensor physically feels for this excessive differentiation of position of the two bodies.  If it detects excessive differentiation, it dumps the trainline air which makes an emergency application.


Both of these concepts seem robust, simple, and reliable for use with conventional air brakes.  Why make it any more complicated?  With ECP brakes, the signal line could transmit derailment data if there were a need for that.  Also with ECP brakes, the signal line could set the brakes simultaneously, and thus mitigate the issue of a detector initiating an emergency application directly from the point of derailment, at some mid-train location. 

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Posted by Euclid on Friday, March 17, 2017 10:16 PM

There won't be any magic here. I doubt that the reaction to a radio UDE tone would ever be for every engineer hearing it, near or distant, to instantly plug their train; it would be handled through the equivalent of a RTC or dispatcher, with human reaction times and communications channels, and instructions relayed to affected trains. Conversely, a dispatcher couldn't see the blowing snow, which was a major factor here, so almost certainly his order to a loaded oil train passing another train would be to brake safely in some service position.

I agree that the reaction to a UDE alert would not be for every engineer hearing it to make an emergency application.  In most cases, even the most affected train would not need to make an emergency application.  But I don’t see how the alert could be processed through communications to the dispatcher and instructions back to the affected trains.  It is an emergency that can call for instant response by those affected.  As the Road Foreman of Engines on the grain train put it:

“You would expect that a train approaching you [i.e. the oil train which was the subject of the warning] to immediately reduce their speed, protect themselves, maybe even stop, as conditions might require. I don't know that there's anything absolutely written in stone other than you'll get your train speed down, control, and you'll -- if I was on the train, we'd proceed looking out for hazards in front of us.”

Of course, in this case, if the engineer of the oil train never heard the announcement, that explains why he did not react to it.  But had he heard the announcement, I think an emergency application would have been the safest course.  “Immediately reducing speed and protecting yourself” could not be accomplished by a service application in this case. 

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Posted by erikem on Friday, March 17, 2017 11:09 PM


Erik -- sorry, I have no idea why I thought that was you.  I have edited the post accordingly.  (I did think it was a bit strange you'd say manual monitoring would be necessary...)

Absolutely no problem, I thought it was rather amusing.

I also aree on issues with the cameras, have enough fun keeping the lens of the back-up camera on our newest car clean and would hate to think how infrequently the lenses on a truck would be cleaned.

There has been a lot of interest in wireless sensors for industrial use driven by a typical cost of $20/ft in the early aughties for factory floor wiring (reported by Wayne Mangess of ORNL). On of the applications was monitoring motor bearings, which would be a bit similar to the truck problem. Energy harvesting was being developed in order for the sensor to be truly wireless.

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