While I welcome a range of discussion on the topic, this thread has divided into a parallel discussion of two completely different brake system concepts. For anybody looking at it for the first time, it will be impossible to realize that. It will look like all the technical features run together, as opposed to being two separate proposals. So, as a result, the thread title will be perceived to offer a solution of enormous technological complexity that is sure to outweigh any advantage.
But to the question at hand: Is monitoring wheel rotation speed really the simplest way to detect a derailment?
If that method is used, I would think you would need to sense the rotation speed of every axle in the train, and compare that rotation rate to the average rotation rate of all the axles. Why can’t you just sense the vibration on each truck and compare that to the normal vibration? A change in vibration at the onset of a derailment seems like it would be a much greater change than a change in axle rotation speed. Thus, the vibration change might be simpler to differentiate from normal, and it has the potential to sense the derailment as early as possible. Any wheel on the ties will be a perfect vibration producer.
There are a couple assumptions in this proposal That I would like to ask about.
Assumption 1: In normal operation the wheels of a rail car all turn at the same rate. Do you know this or is this an assumption? When going around a curve, if the lead truck is rolling on the inside rail and slipping on the outside rail, and the trailing truck is rolling on the outside rail and slipping on the inside rail, the wheels will be turning at incrementally different rates. If the brakes are applied in normal operation and the brakes apply at different effectiveness on different axles, causing the wheels to turn at different rates, will the system interpret that as a derailment? What happens if the lead axle has a brand new wheel and the trailing axle has a near condemnable wheel? Since the wheels are of different diameters, they will turn at different rates. A 33" wheel has 611 rev/mile, a 31" wheel (1" wear) has 650 rev/mile. A 36' wheel has 561 rev/mile and a 34" wheel has 588 rev/mile.
Assumption 2: If the wheels of a car derail, it will they always turn at different rates. Do you have any proof of this or is it an assumption? If you include variance to accommodate wheel wear and braking differentials, do you know that a derailed wheel turns slower than those variances? If normal wear has a differential of 30-40 rev/mile will the differential of a derailed wheel be more than that? Do you know that or is it an assumption?
Assumption 3: If a car derails, one of the outboard axles will always be derailed. What happens if just an inboard axle derails?
Assumption 4: Both ends of the car can't derail at the same time. If both ends derail at the same time or near same time (rail rolls over) will derailed wheels turn at rates with a variance greater than the normal variance?
With a locomotive wheel slip system, the most it does is adjust the power to the axle, so if it is "wrong" the consequences are relatively minor. In this case if there is a false positive, the train catastrophically fails (it stops the whole train). Big difference in the requirements for accuracy.
Dave H. Painted side goes up. My website : wnbranch.com
erikem Hmm, time for some numbers...
Hmm, time for some numbers...
Now we're gettting somewhere.
I presume we are talking about using this system as a one-time emergency device -- would the heat dissipation be sufficient to keep the coil and/or leads from softening and melting after the braking run is finished. What material are we using to keep the turns insulated from each other that will take the temperature 'long enough' and not crack as the copper expands? Does it matter in a one-time system if it cracks, so long as it provides the operational insulation (there won't be corona shorting through the cracks at no more than several V)
How do we guarantee that the braking is equally applied to both rails, if the system is applied to the truck? I would surely wire them in series. At this deceleration rate, what force would be applied to rotate or skew the truck if it goes over a conventional frog -- the chain system might help this but I think would need a fast-acting tensioner.
I am too lazy to calculate the field decay with dropping voltage, but for 'constant deceleration' you would want the field strength to decay proportional to momentum, no? So the peak current would only apply at higher road speed, and in any case one of the other uses of a magnetic-brake system is to get the momentum down to where conventional air brakes can work effectively. I will figure out this curve and the control modality to achieve it later, if erikem doesn't do it first.
Something very significant, perhaps, is that these brakes ARE the practical answer... if modulated short of melting... to the kind of runaway aggravated by brake fade due to composition shoes. If the brake can generate 5mphps decel in emergencies, it is surely adequate for pulling down speed to where conventional brakes can re-establish authority... the operational difference with dynamic braking being that the 'magnetic' deceleration is no longer dependent on complex locomotive systems and logic, and applied through a relatively small number of relatively expensive wheels.
I do think that it would make sense to run this at a higher nominal voltage than that which is close to the supercap punch-through, and perhaps to use one of the self-healing construction methods. That might allow use of the system in blended operation at higher speed, and more apropos to the present discussion, allow longer or repeated application at relatively low power for the calculated distributed differential braking that was an essential point of Dave's system for derailments.
There remain a number of legal, political, and regulatory concerns with the system that we might address.
Decelostats have been around in railroad applications for years, no need to re-invent. Mostly used for disc braking on passenger cars.
RSS
Again, there may be more sophisicated systems, but two alternator comparison method is already in use in locomotive slip control and can just as ealisy be applied as derailment detection. But if you wis h to replace the battery wiht sjuercaps, OK if the supercaps will do the job adequately. The magnetic track brake is a separate issue. Electric power is still required on the car. Head end power can help, but we want the car's electrically controlled brake, and the magnetic track brakes if applied, to work should the car be behind a break-in-two.
Fusing current for 10 awg is 500A at 8+ seconds, 6 awg can take 1000A for about 10 seconds. To get 200A at the magnet terminals and with a 12V supply, one would need to keep the wire length to 60' or less with 10awg copper wire and on the order of 150 feet with 6awg wire. 1000F at 2.5V would be 2500 coulombs, so the capacitor would be discharged in 12.5 at a constant 200 amps - possibly marginal with respect to 10awg wire, but no problem for anything much larger. Note that the current will decay as the capacitor discharges, though that may be a feature as opposed to a bug.
A quarter g braking effort will result in a 5.5 MPH/sec deceleration, so 10 seconds of baking at that rate will bring the car to a stop. There isn't much point in going to magnetic track brakes unless the retardation is at least a quarter g.
What I've proposed is probably nowhere near optimal, but close enough to indicate that it is within reason. I've seen electromagnet designs crazier than this (unusual NMR magnets).
- Erik
tree68No question there. The bulk of my experience is with capacitors in tube and transistor electronic circuits, not high-capacity applications.
Hmmmm... YOU wouldn't have a copy of the 'bad electron' proposal made for the Navy during WWII, would you? The one about the 'static' and noise in contemporary AM circuits being due to bad electrons, that were filtered out and forced to charge an 8"-nominal-diameter capacitor, which was then put into one of the ship's guns... well, drift speed of electrons in salt water is not all that great, so you could work some clear traffic until the bad electrons got back to the hull...
tree68I do have to question, however, just how long the capacitors will be able to maintain sufficient current through the brakes. I don't recall that anyone has said how long it would have to be (unless I skimmed over it), so we have a moving target there.
The current would be limited by resistance in the normal manner for these things, if there weren't more explicit provision for 'active' limiting. I'm surprised there isn't something on the Net somewhere that would explain this.
I am by no means sure I trust the idea of a very fast capacitor discharge through magnet wire, especially if wound around a formed core, with the idea that the current will be of such short duration that resistance heating will be 'acceptable'. I don't see the brakes possibly working in the time interval quoted -- perhaps I am simply taking something firmly tongue-in-cheek with too much seriousness.
I do think the setup would be better served by a good modern battery stack with the ultracaps used as 'charge buffers' to limit the rate of change in charge and discharge that the battery chemistry and structure would otherwise suffer. The idea of using the alternators to power the track brakes directly strikes me as a very expensive, complex attempt to recreate the Loughridge Chain Brake with only some of the historical faults addressed... ;-}
OvermodI think you are lamentably behind the times regarding capacitor technology.
No question there. The bulk of my experience is with capacitors in tube and transistor electronic circuits, not high-capacity applications. I have to go with what I can find on the 'Net.
I do have to question, however, just how long the capacitors will be able to maintain sufficient current through the brakes. I don't recall that anyone has said how long it would have to be (unless I skimmed over it), so we have a moving target there.
Short 1000F and you will have a memorable experience.
Been there, done that - maybe not 1000F, but it was the HV for a large CRT display in a piece of weather equipment... It made quite the snap when we discharged it.
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...
tree68 A one farad capacitor will range in size from a tuna can to a 1 liter soda bottle, depending on the voltage involved. According to How Stuff Works, replacing an AA battery with a capacitor would require a device capable of 11,080 farads... We'll just have to send out workers with boatloads of penlight batteries to keep those cars ready to go...
A one farad capacitor will range in size from a tuna can to a 1 liter soda bottle, depending on the voltage involved.
According to How Stuff Works, replacing an AA battery with a capacitor would require a device capable of 11,080 farads...
We'll just have to send out workers with boatloads of penlight batteries to keep those cars ready to go...
I think you are lamentably behind the times regarding capacitor technology. If you Google 'ultracapacitor' and look at the size of a multifarad capacitor you will find it considerably smaller -- and far more susceptible to damage by even slight overvoltage -- than the tuna cans and so on you mentioned.
One thing about the 'thousand farad' instantiation is that its output to the brake would almost certainly not be running at the 2V nominal output; the individual supercaps/ultracaps would be in strings.
Another thing that makes ultracaps different from penlight batteries is the very low effective internal resistance. Short a 3V battery terminal, and the current is limited by the characteristics of the internal chemical reactions. (But see the YouTube video with the hundreds of 9V radio batteries in series...!) Short a 3V lithium-ion battery and you might get a fire. Short a 1-farad capacitor even at 2V and expect to see something interesting. Short 1000F and you will have a memorable experience.
It does look a bit amazing that there are so many electrons stowed up in one little penlight battery (and in the same general range of output voltage as the supercap, too) but remember the definition of a coulomb, and then of a farad. The difference is what's involved in getting all those electrons to stay inside the can as opposed to inducing them to go from one place to another. If you look at the history of electrical technology, its early beginnings (in Europe, not in India) are in electrostatics -- but the practical uses develop first with the invention of the 'voltaic pile' and then by the recognition that electromagnetics and induction give far more power, and at higher potential voltage (pun intended) than a standard-potential chemical reaction...
Overmod One th-th-th-thousand f-f-f-farads on a r-r-railroad car? With wires hanging down the outside of the truck frame? Nice arc source for the oil if it gets out, perhaps -- or to make a hole in the car, perhaps?
One th-th-th-thousand f-f-f-farads on a r-r-railroad car? With wires hanging down the outside of the truck frame? Nice arc source for the oil if it gets out, perhaps -- or to make a hole in the car, perhaps?
Sure! A Maxwell 1500F capacitor comes in at 61mm dia and 85mm long. Keep in mind that it is rated for 2.7VDC, and lifetime would be longer if kept at 2.5V. Five of these puppies in series would give 12.5V, which is WAG for the drive voltage for the track magnet.
For RR service, I would encapsulate the caps in an electronic grade epoxy along with the FET switch to energize the magnet. Charging and voltage sensing would be done through current limited leads. I'd be less scared of dealing with an ultracap than a Li-ion battery with similar short term power ratings.
On a related note, I'd contend that ultracpas would be much nicer for a "Green Goat" switcher than lead-acid batteries.
And then there are the fun uses if the cap array is stolen some dark night...
I think I'll pass on ultracaps for this particular application, thank you. I only hope others do, too.
The safe oil train system that I am proposing uses ECP brakes, but I am not calling for the development of ECP braking, since this braking system already exists fully developed. I am just calling for its application to oil trains. However, I am proposing a small control modification to the ECP braking system that does not currently exist. That is the part that changes the braking performance in response to a derailment.
But, aside from what I am proposing, ECP braking alone would offer a substantial benefit over standard pneumatically controlled pneumatic braking of our present universal system. ECP braking applies more quickly than standard PCP braking. The quicker application reduces stopping distance by 30-70%.
Some here have said that braking of the cars behind the derailment cannot possibly keep up with the deceleration of the cars that have derailed. That may be true in some cases, but generally I think that claims of how fast those derailed cars will stop have been exaggerated. And I also think that the imagined problem fails to take into account, the enhanced stopping power of ECP brakes working to slow down those trailing cars.
Another benefit of ECP braking is that, not only is application quicker, it is also simultaneous, unlike conventional air brakes which propagate the application sequentially from one car to the next over a period of time. This propagation lag time creates slack action that can actually cause a derailment. So ECP brakes actually prevent derailments in some cases by virtue of their simultaneous application.
Therefore, considering the fundamental advantages of ECP brakes alone, I expect and predict that the railroads will apply ECP brakes to oil trains. It will make them safer. It is the most obvious advantageous application because oil trains are said to lacking in safety. And it will show the regulators and the public that the railroads take the problem seriously and are doing something big about fixing it.
ECP brakes are perhaps the most high profile advancement in safety and performance that the industry currently has. Considering the fact that the railroads would like to begin their ECP introduction with specialized service as a way to ease into universal application, putting ECP brakes on oil trains seems like a no brainer.
Here is an informative paper on ECP brakes: http://www.uic.org/cdrom/2001/wcrr2001/pdf/sessions/1_6/465.pdf
But the alternators also serve as the derailment detector pickups, are existing technoilogy in both applcations. Remember that it is the difference between the speed of the front and the rear axles that singals a derailment has occured.
Placing the alternator on the end caps of the roller bearing makes sense to me as well, though my preference would still be to use ultracaps to energize the magnet. My concern with derailments is from having a heavy chunk of metal dangling by springs, and what happens if one of the springs break.
Running some numbers, a four inch square with a 1 Tesla flux density will be good for about 10,000 pounds of force, which would give very useful retarding force. With a gap of 1mm between the pole face of the magnet and the rail, this would need one the order of 20,000 amp turns, 100 turns would need 200 amps Noe that 10 awg wire can handle the current for the time involved). 200 amps for 10 seconds would be 2000 coulombs, which could be provided by a 1000F ultracap charged to 2 volts (latest caps are good for 2.5V long term). Number of caps in series would depend on resistance and inductance, along with the change in coil voltage due to the field increasing when the pole faces approach the rails.
Looks doable, though not sure if it make sense.
Euclid This fireball crisis is more of a marketing problem for the railroads and oil industry than it is an engineering problem. It is interesting to note that, although this problem applies to the oil industry as well as the railroads, the main media thrust focuses on the culpability of the railroads for their derailing trains. The media seems to dismiss the Bakken oil volatility and the mislabeling by the shippers. If it were just an engineering problem, the railroads could take comfort because much of that problem is beyond their control. But since it is a marketing problem, the problem can be anything that the media says it is. You can say that it is not a problem because the media does not know what they are talking about—that they exaggerate the danger of oil while ignoring the more dangerous materials that are shipped by rail. But it does not make any difference. If the media says the problem is oil-by-rail, then that is the problem. You can’t end the problem by disproving the media. You can’t defeat the power of the press by scoffing at it. A Senate hearing on this rail safety problem had been scheduled for last Thursday, but was cancelled due to snow. The marketing problem will be on full display once this hearing is under way. Senators will expect the railroads to ensure the safety of people living along the rail lines because the premise of the problem is that the railroad companies are placing these people at risk for death and injury every day now with the rising oil traffic. “Ensure the safety” does not mean that it is enough to create the probability that fewer people will be killed or injured. There is also the implication that Senators expect a very quick solution to the problem because they refer to the problem as being critical. Against this backdrop, the industry will tell the Senators that the problem is being exaggerated; that the media is wrong; and that rail is the safest form of transportation. And then the industry will offer a purely engineering based solution to the problem that will take several years to achieve. The Senators will want to know if the industry’s solution will ensure the safety of people along the rail lines, and the industry will tell the Senators that “nothing is 100% certain.”
This fireball crisis is more of a marketing problem for the railroads and oil industry than it is an engineering problem.
It is interesting to note that, although this problem applies to the oil industry as well as the railroads, the main media thrust focuses on the culpability of the railroads for their derailing trains. The media seems to dismiss the Bakken oil volatility and the mislabeling by the shippers.
If it were just an engineering problem, the railroads could take comfort because much of that problem is beyond their control. But since it is a marketing problem, the problem can be anything that the media says it is.
You can say that it is not a problem because the media does not know what they are talking about—that they exaggerate the danger of oil while ignoring the more dangerous materials that are shipped by rail. But it does not make any difference. If the media says the problem is oil-by-rail, then that is the problem. You can’t end the problem by disproving the media. You can’t defeat the power of the press by scoffing at it.
A Senate hearing on this rail safety problem had been scheduled for last Thursday, but was cancelled due to snow. The marketing problem will be on full display once this hearing is under way. Senators will expect the railroads to ensure the safety of people living along the rail lines because the premise of the problem is that the railroad companies are placing these people at risk for death and injury every day now with the rising oil traffic.
“Ensure the safety” does not mean that it is enough to create the probability that fewer people will be killed or injured. There is also the implication that Senators expect a very quick solution to the problem because they refer to the problem as being critical.
Against this backdrop, the industry will tell the Senators that the problem is being exaggerated; that the media is wrong; and that rail is the safest form of transportation. And then the industry will offer a purely engineering based solution to the problem that will take several years to achieve. The Senators will want to know if the industry’s solution will ensure the safety of people along the rail lines, and the industry will tell the Senators that “nothing is 100% certain.”
Posted by Norm48327
onSat, Feb 15 2014 5:31 PM
****************************************************************************
Norm,
You mentioned earlier that you thought I was on the right track with the marketing component of my safe oil train idea.
So I am just putting the problem into perspective by explaining what I mean by a marketing problem. Just because I am pointing out a peril to the industry does not mean that I hate the industry. Ignoring the peril will not make it go away. Pointing it out might be useful if the industry does not see it. You can’t sidestep a problem if you don’t realize it is there.
There are indeed haters in this equation, but I don’t see them as railroad haters. They are oil haters, and their greatest current leverage against oil is in impeding of oil shipping by rail. Public safety is their most potent weapon, and you can bet that their viewpoint will be present at the Senate hearing.
The hearing will be very interesting to watch. It is a quest for answers, and answers will be given. So far, I have not heard any answers other than making tank cars stronger and getting the trains a safer distance from the public. In my opinion, that solution does not match the problem. It only very slowly nibbles at the margins of the problem while the Senators and the public expect an end to the problem now. And if they don’t hear what they want to hear from the industry, they will solve the problem on their own.
From a marketing perspective, if you can’t solve the problem 100%, and do it now; then make the public and the regulators believe that you will.
I agree, that that is far-and-away the best approach for the alternator, and allows the wheel sets themselves to remain standard. Either slipring alternators or rotating magnets could be used.
erikemAs Dave said, the electromagnet needs to be in close alignment with the rail as the induced field and resulting mechanical force are inversely proportional to the air gap.
What I think Dave has been advocating is the kind of track brake that is suspended by springs, so that when it is activated it 'clamps' electromagnetically down on the railhead. It is faced with material that optimizes friction but also provide minimal wear, 'welding' transfer of shoe material, etc. The braking action is a combination of induced eddy current and straight friction from the clamping between the brake magnet(s) and the steel reilhead.
If his design is similar to what mine was, the 'contact shoe' is somewhat reminiscent of the old 'diamond' composition shoe from the late 1800s (whatever it was called) in that part of the contact area is optimized for friction, and the rest is optimized to carry the magnetic lines of force. So when the brake and shoe are applied, the magnetic field can be taken up as near saturation as possible, without any air gap other than that induced by things like surface-wear mismatch or ablation from the friction material. (I had several versions in which the shoe was made similar to a patterned magnetic clutch, with all the elements separately able to move vertically in a carrying frame, so that independent modulation of the electromagnets and the effective field strength through the magnetic circuit could be done independently.)
Now would be a good time to mention that the 'ideal' place to implement this type of brake is on low-frame or well cars, where the underframe structure itself is close enough to the railhead that the track brake can be carried on the car frame completely independent of the trucks. My system was intended primarily for the same sort of purpose as the hydrokinetic brake on the British APT-E -- very prompt and positive deceleration from comparatively high speed down to 'normal' braking speeds -- without requiring large amounts of energy to be transferred through the small contact patches between wheel and rail, or causing changes to wheel geometry as a consequence of high brake wear. (This was back in the days when everybody 'knew' a train could not be driven above roughly 310 mph with motored wheelsets, because no further energy could be transferred through adhesive contact of wheel and rail for acceleration... and the 'smart action' was on LIMs or similar noncontact propulsion to also provide the high-speed, and even some of the low-speed, braking without compromising either sensitive suspension movement or sensitive wheel structure and tread-profile integrity).
I think I specifically rejected the idea that you could harvest suspension energy to charge the system (on oil trains), in very large part because neither extended nor particularly long range of motion is achievable in a three-piece truck system that has a large ride-height disparity between loaded and empty.
Meanwhile... are not belt- or Spicer-driven generators about to be illegal on passenger cars? And I would sooner stick my hand in a cobra's mouth than say I was going to integrate part of the alternator into the wheelset, or attach it to the wheelset in a way that covers some of the wheel so it can't be immediately inspected for cracks or other incipient damage...
(I'd think the best place to put the alternator -- provided you can make it small enough, and well-enough encapsulated from harsh environment -- would be outboard of the roller-bearing endcap, driven by something like a splined plate clamped by the roller-bearing cap endbolts, and held by a full elastomer mount in a bracket attached to the sideframe, arranged so that if the alternator seizes for any reason it will not impair wheelset rotation. This should incidentally greatly simplify how the connections from the 'generator' to the rest of the car can be made, and is of course as accessible as any alternative, and drop-dead simple to apply to almost any truck or wheelset...)
I am trying to avoic Buck Rogers stuff. Rotating magnet alternaters would be just fine, but alternators using slip rings are already available in small packages. Again, with uniform braking, I cannot imagine magnetic track brake making things worse. I do believe the concept should be tested first with a prototype car or pair of cars, then with a 50 or 100 car train. The question is: Is the shorter stopping distance worth the extra complexity of the trucks and control system? The derailment singalling features of the alternators would be preserved with a rotating magnet alternator design, and if such equipment is available in the small size required, that would be preferable of slip rings, I agree. But energy recovery from spring bounce etc looses completely the derailment detection function, which is equally important. I do not know whether the alternator on the outer axle of each truck should be built into the wheel bearing, be belt driven, grear driven, or even integral with the wheel, as in Magnet Motor's bus and tram motors (Germany), also a frim that make wheel motors in Derby, England (Stored Energy Systems, Ltd.?), and has a good businss in "Rail Cats" for moving lightweight railcars in yards and shops..
In summary: The two alternator wheel rotation comparison system for derailment detection is a robust system using existing technology and only slightly modified existing equipment.
Uniform braking with uniform cars is essential for the fastest possible safe braking in any event and requires electric control.
There has never been a case in railway history where magnetic track brakes have made any situation worse, and if braking is utiform with uniform equipment, I consider the idea of it making things worse with these brakes as not reasonable. But the question remains whether the shorter shopping distance obtained is worth the added complexity. Each magnetic brake mechanism woujld be screwed tightly to the sideframe below the bolster, to avoid varying distance between mechanism and rail, as they were on the C&LE cars, and are on those preserved.
The amount of added rolling resistance added by the alternator will be trivial, and almost non-existant when the battery is charged and the train running with brakes released. Head-end power can also be accomodated, and then each car's battery is there primarily for break-in-two emergencies only.
Overmod Would you not use a permanent-magnet rotor (in this age of cheap NdFeB) and thereby escape the need to have slip rings, either? Then you also need no external excitation (I find this is very, very, very often the failure point of exposed vehicle charging systems...)
Would you not use a permanent-magnet rotor (in this age of cheap NdFeB) and thereby escape the need to have slip rings, either? Then you also need no external excitation (I find this is very, very, very often the failure point of exposed vehicle charging systems...)
A permag rotor sound likes a good idea to me, though the devil would be in the details of where the alternator is mounted. What would make a bit more sense to me is an "energy harvesting" style of generator, perhaps nestled in the spring box of the truck to keep a battery or supercap charged. I would guess that the braking effort would only need to last for a few seconds. Designing the electromagnet coil for short term operation will also cut the amount of conductor needed.
I was under the impression that most of these trucks were drop-equalizer designs, with a 'sideframe' that remains invariant under weight transfer or other thrust conditions. My understanding is that the sideframes on three-piece trucks are always 'thick' enough that there's no way you could bolster-mount an electromagnetic brake and have it be in line with the railhead unless both offset and thin enough to go in the space under the sideframe. Where, if it breaks loose or jams, it will quickly and probably very effectively cause, rather than prevent, derailments. The same is very likely true of a brake suspended directly under the sideframe, say from the attach points for skew braces. I wonder if it is possible to make the brake 'wide' laterally, perhaps with multiple sets of windings, and use a (rather simple!) sensing method to actuate only the parts of the brake that 'magnetically couple' to something underneath, regardless of how far displaced from 'centerline' of the magnetic brake you get on curves (or other conditions, named or expectable). How far out could the structure project before it starts being a bane to crewpeople walking a train 'on the road' with restricted walkway access in the dark?
I was under the impression that most of these trucks were drop-equalizer designs, with a 'sideframe' that remains invariant under weight transfer or other thrust conditions. My understanding is that the sideframes on three-piece trucks are always 'thick' enough that there's no way you could bolster-mount an electromagnetic brake and have it be in line with the railhead unless both offset and thin enough to go in the space under the sideframe. Where, if it breaks loose or jams, it will quickly and probably very effectively cause, rather than prevent, derailments. The same is very likely true of a brake suspended directly under the sideframe, say from the attach points for skew braces.
I wonder if it is possible to make the brake 'wide' laterally, perhaps with multiple sets of windings, and use a (rather simple!) sensing method to actuate only the parts of the brake that 'magnetically couple' to something underneath, regardless of how far displaced from 'centerline' of the magnetic brake you get on curves (or other conditions, named or expectable). How far out could the structure project before it starts being a bane to crewpeople walking a train 'on the road' with restricted walkway access in the dark?
The C&LE cars used an archbar truck and relatively small wheel diameter, so the magnetic track brakes could not have taken up too much space. As Dave said, the electromagnet needs to be in close alignment with the rail as the induced field and resulting mechanical force are inversely proportional to the air gap.
I'd also want some evidence that the brake would prevent more accidents than it would cause.
EuclidYou can say that it is not a problem because the media does not know what they are talking about—that they exaggerate the danger of oil while ignoring the more dangerous materials that are shipped by rail. But it does not make any difference. If the media says the problem is oil-by-rail, then that is the problem. You can’t end the problem by disproving the media. You can’t defeat the power of the press by scoffing at it.
Historical perspective (not media):
The NTSB was already saying the DOT 111s were unsafe in accident reports in the 1990s (as early as 1991). NTSB/SS-91/01 questioned "the safety of 111A tank cars. It determined that this classification of tank car has a high incidence of tank integrity failure when involved in accidents and that certain hazardous materials are transported in these tank cars even though better protected cars (less liable to release the transported product when involved in accidents) are available."
Why has it taken 23 years to address this issue? Perhaps not solely railroad responsibility, but in 1991 there was no Bakken crude. All of this sounds like blame some other agency or industry and meanwhile nothing was done in spite of strong evidence of the hazard. That is negligence.https://archive.org/details/ensuringrailroad003725mbp
C&NW, CA&E, MILW, CGW and IC fan
Ken, that's cold. That's REALLY cold!
Since it would be highly beneficial to prevent the derailed trucks from pivoting on their center bearings after derailing, I have thought about truck safety chains for this safe train concept. However, up until about now, I have never completely understood the theory behind truck safety chains. They were once common on passenger car trucks and nearly universal on steam locomotive tender trucks.
But what I never understood is this: Since the chains need considerable slack to allow the trucks to pivot in normal operation, a derailed truck would also be allowed that amount of pivot which might be perhaps 30 degrees to the line of track. Yet, if a derailed truck were allowed that much pivot, it would be very likely to quickly twist to that limit upon derailment. That much pivot on the derailed truck would cause enormous skew stress and probably cause the truck to break its center pin and disengage its center bearing from the car bolster; despite the presence of safety chains.
But what I now realize is that preventing that truck separation is not the point of safety chains. They cannot be loose enough to permit operational pivot and yet be tight enough to prevent separation from twisting during a derailment.
So it is a forgone conclusion that the truck will separate upon derailment even with safety chains. But the safety chains come into play after the truck separates. When the truck separates, it drops back until the two leading direction chains tighten. Then upon tightening, those two chains force the truck to straighten back out to run in line with the track. It will be running offset to the rear of the normal position by about a foot or so; and it may hunt side to side somewhat; but the two chains will tend to re-center it side to side, and keep it tracking in line with the track.
daveklepperOne of the two alternators required for my derailment notification is required anyway to keep the battery charged for any electrical equipment to work and is not a maintenane item. Older dc generators were, with brushes and commutators, but not alternators with rectifiers.
dakotafred Norm48327 Ya know Bucky, Your entire post sounds like it comes from a rail hater rather than a railfan. If you're referring to the post, Euclid's, immediately above your own, I can't agree. To me, Euclid was just pointing out the rails' PR problem, no matter how faithful the rails (and shippers, and manufacturers) may be in engineering and operating for safety. The ass's bray of the ignorant media is what gets the attention of the public and the politicians, and can't be engineered away. That's what Euclid was saying.
Norm48327 Ya know Bucky, Your entire post sounds like it comes from a rail hater rather than a railfan.
Ya know Bucky,
Your entire post sounds like it comes from a rail hater rather than a railfan.
If you're referring to the post, Euclid's, immediately above your own, I can't agree. To me, Euclid was just pointing out the rails' PR problem, no matter how faithful the rails (and shippers, and manufacturers) may be in engineering and operating for safety.
The ass's bray of the ignorant media is what gets the attention of the public and the politicians, and can't be engineered away. That's what Euclid was saying.
Euclid = Bucky (The poster formerly known as Bucyrus)
Overmod daveklepper It may very well be that there is not room for magentic track brakes between the bottom of the regular three piece freightcar truck and the top of the rail . If the normal light rail type track brake won;'t fit... The thing is that the normal type of 'transit' track brake isn't going to have the structure to 'tie into' that it would need to achieve the desired deceleration rate for a loaded car's mass. But this brings up a slightly different potential scenario: if the magnetic brakes are not 'fully' capable of decelerating the train, they can certainly implement some degree of differential braking independent of the modulation of the air-brake system itself. And that, in and of itself, might make even a 'discontinuous' system of magnetic brakes on some of the cars a worthwhile project to consider for some circumstances... When I looked into the idea of magnetic brakes many years ago, I assumed that they would have to be mounted on a 'sled' of some sort, running on its own small carrier or even guide wheels, and connected to the centersill of the car with some sort of linkage capable of taking the full braking moment without putting the wrong kind of thrust on the car. Now one idea of this was that if a truck were to derail, the sled (and the electromagnetic bar and 'shoe') would still largely be aligned with the rail for a perhaps significant time, during which the magnetics might tend to hold the car more 'centered' in the available clearance gage than might otherwise be the case. (Just in case anyone misses it -- one reason I gave up on this is the derailments that would occur if any part of the 'sled' or its linkage wound up where it shouldn't be... so don't anyone start up threads on a third bold new method of arresting oil trains in their tracks... ;-} ) I think the rest of my proposal, electric brake control, uniform braking, and derailment detection though use of locomotive wheel-slip technology, measuring the rotation of the front and rear axles of each car and comparing the front and rear axles of each car... Except that we will already have a much better derailment detector in the little RFID module glued on each sideframe end, above the bearing carrier, that is recording and transmitting shock information from wheel flats or out-of-roundness. The first sign of a derailment isn't going to be differential wheel rotation nearly as soon as it's significant shock, no? Then all you need is a small encoder on the bolster that measures absolute truck swing, and the necessary PAN-scale connectivity and small transmitter needed to signal 'derailment' to the PTC system that will ... well, modulate what braking method or other special systems are involved in stopping the train as safely as possible. Cheap, easy, ACTUALLY robust in an engineering sense... and synergistic in what it provides operating and maintenance people. Not that I disagree with encoders on the wheelsets, but there's so much more maintenance and potential failure points/modes involved with that. If you do, I'd engrave Hall-effect-suitable 'teeth' on the wheelset rims, and let a periodic pass through retarders keep 'em faced and trued... and put the sensor carriage on the brake-shoe assembly somewhere...
daveklepper It may very well be that there is not room for magentic track brakes between the bottom of the regular three piece freightcar truck and the top of the rail . If the normal light rail type track brake won;'t fit...
It may very well be that there is not room for magentic track brakes between the bottom of the regular three piece freightcar truck and the top of the rail . If the normal light rail type track brake won;'t fit...
The thing is that the normal type of 'transit' track brake isn't going to have the structure to 'tie into' that it would need to achieve the desired deceleration rate for a loaded car's mass.
But this brings up a slightly different potential scenario: if the magnetic brakes are not 'fully' capable of decelerating the train, they can certainly implement some degree of differential braking independent of the modulation of the air-brake system itself. And that, in and of itself, might make even a 'discontinuous' system of magnetic brakes on some of the cars a worthwhile project to consider for some circumstances...
When I looked into the idea of magnetic brakes many years ago, I assumed that they would have to be mounted on a 'sled' of some sort, running on its own small carrier or even guide wheels, and connected to the centersill of the car with some sort of linkage capable of taking the full braking moment without putting the wrong kind of thrust on the car. Now one idea of this was that if a truck were to derail, the sled (and the electromagnetic bar and 'shoe') would still largely be aligned with the rail for a perhaps significant time, during which the magnetics might tend to hold the car more 'centered' in the available clearance gage than might otherwise be the case.
(Just in case anyone misses it -- one reason I gave up on this is the derailments that would occur if any part of the 'sled' or its linkage wound up where it shouldn't be... so don't anyone start up threads on a third bold new method of arresting oil trains in their tracks... ;-} )
I think the rest of my proposal, electric brake control, uniform braking, and derailment detection though use of locomotive wheel-slip technology, measuring the rotation of the front and rear axles of each car and comparing the front and rear axles of each car...
Except that we will already have a much better derailment detector in the little RFID module glued on each sideframe end, above the bearing carrier, that is recording and transmitting shock information from wheel flats or out-of-roundness. The first sign of a derailment isn't going to be differential wheel rotation nearly as soon as it's significant shock, no? Then all you need is a small encoder on the bolster that measures absolute truck swing, and the necessary PAN-scale connectivity and small transmitter needed to signal 'derailment' to the PTC system that will ... well, modulate what braking method or other special systems are involved in stopping the train as safely as possible. Cheap, easy, ACTUALLY robust in an engineering sense... and synergistic in what it provides operating and maintenance people.
Not that I disagree with encoders on the wheelsets, but there's so much more maintenance and potential failure points/modes involved with that. If you do, I'd engrave Hall-effect-suitable 'teeth' on the wheelset rims, and let a periodic pass through retarders keep 'em faced and trued... and put the sensor carriage on the brake-shoe assembly somewhere...
My intent was mounting on the trucks because that is the only way the track brake can be aligned with the rail on all curves. Note that the side frame of the truck is outside the rail and wheels, and the track brake can be inside, rather than below, the side frame, but in line with the wheels. The Cincinnati and Lake Erie and Indiana cars, also later of course on CR&IC and LVT, had track brakes with this arrangemennt. You could barely see the bottom of them, and only when lookiing up close, but they were there and worked fine when needed. The space on the C&LE trucks is approximately the same as a typical freight-car truck.
One of the two alternators required for my derailment notification is required anyway to keep the battery charged for any electrical equipment to work and is not a maintenane item. Older dc generators were, with brushes and commutators, but not alternators with rectifiers. Sure, you can have sensors all over the place on each truck, but I think my proposal may be more cost effective and quicker to implement.
I do agree it's a PR problem. Perhaps it's simply the way I interpreted his post. It was the last paragraph I thought was basically condemning the powers that be for paying it lip service rather than saying "We're working at correcting the problem".
And your comment on the media was appropriate.
Norm
The ass's bray of the ignorant media is what gets the attention of the public and the politicians, and can't be engineered away. That's what Euclid was saying, I think.
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