Do they always occur in response to a service application?
Or do they sometimes occur spontaneously when no other braking event is occurring?
If a train is found to contain a kicker, is there any way to determine which car in the train is the kicker?
Is there ever an occurrance of one car with some type of brake valve defect that causes it to dump its air and dynamite the whole train when no service application is occurring?
Not always, but that is the normal occurrence.
Train lines leak, and sometimes, the pressure drop is just enough to set the kicker off, but most often the service reduction is the initial event.
You can find a kicker, but it depends on where you are, how long the train is, how much time you have.
While the engineer recharges the brakes, you walk to about the half-way point, and have him set the brakes.
You listen, and can hear the “emergency” application and the air rush towards you; it will start from the kicker and work out both ways, towards the front and rear of the train.
If the sound comes towards you from the rear of the train, the kicker is in the back half…start from scratch, have the engineer recharge the brakes while you make your way half way down the rear of the train, and start over…process of elimination will get you close enough to the kicker to finally hear it set off the brakes and you can isolate the car, which means you can sometime cut the brakes out on that car, but that also means you have to stop and set it out first chance, and on some roads it means you have to proceed to that point at restricted speed.
The “transient phenomenon” challenge = occurs inconsistently sometimes, but not every time, and not predictably or in reliable accordance with any conditions that are easily discernable in the field. (Happens often with automobiles, too - ask any mechanic who deals mostly with the public . . . [:-^] )
You know with all this talk about dynamiters, I’ll probably have one in my train on my next trip. I haven’t had one for quite a while, so I’m probably due for one anyway.
While any type of freight car can have a defective control valve that “kicks” or “dynamites,” it seems like coal trains (loaded and empty) seem to be more prone to this. That would give creedence to the post about dirt and dust fouling the parts of the control valve.
Dynamiters also seem to come in two varieties. Those that go anytime you use the air and those that only go when you’re going slow. About 20-25 mph or less. I have no idea why some only go at slow speeds.
One trick taught to me when you have a dynamiter is to move the automatic brake valve to minimum service for about a second and then back to release. Do this a couple of times before leaving it at minimum to start your brake application. Experts will say that has no effect, it’s just coincidence that the dynamiter doesn’t go when doing this. My experience is that the coincidence happens probably about 3/4 or better using that trick. My theory is that you get the air starting to “move” but not enough to trigger the dynamiter. The idea behind cutting out the air brakes on the first car was to “slow” the application to the train. The rules prohibit cutting out the air brakes on more than two consecutive cars because that could keep an emergency application from properly being transmitted.
While dynamiters are a pain in the backside, there usually is no urgency to locating which car(s) are doing it. You just deal with it the best you can. At lease when you have one you are expecting it. Not like when you’re just rolling along and the air goes for no apparent reason.
Thanks for your explanations and information on this. What I did not realize until asking here is that a kicker is triggered by a service application. I had the impression that they were just a spontaneous event that would occur when running with brakes released.
Part of my curiosity about this stems from a short anecdote in Trains back in the 1990s called “God Is Not the Engineer.” I can’t recall all the details, but a trainmaster accused an engineer of bad train handling, and he told the trainmaster that it was an act of God because there was a kicker in the train. So he told the trainmaster that the problems with train handling was an act of God and God was not the engineer. The engineer even told the trainmaster which car was the kicker.
So I asked an engineer if there was any way to determine which car in a train was the kicker if there was one in the train. He told me that the only way he knew of would be if it were daytime, if there was fresh snow, and you were looking back along the train standing still, it might be possible to see a puff of snow at the kicker when it kicks.
But if a kicker will kick in reaction to a service reduction, then I can see how you could actually track it down if there was time by making the kicker kick and listening to the sound as Ed mentioned.
Another part of my curiosity was that article in Trains where a wreck inspector discovered the cause of a derailment to have been a kicker. But in that case, the wreck inspector made the discovery by digging into the heap of cars and discovering a kicker. Unless I am missing something, that would be absolutely impossible. &
Link to a Transport Safety Board of Canada report with an analysis and excellent discussion of this subject - see esp. the Appendices and the references:
Railway Investigation Report - Main Track Derailment - Ottawa Valley Railway/ RailAmerica, Inc.
Train 556-17 - Mile 1.88, North Bay Subdivision - Near Chalk River, Ontario - 20 June 2000
The following 2004 TSB report is on a 2001 derailment caused by excessive ‘buff’ forces after an emergency brake application was initiated by the train crew:
In particular, this photo of a upward-buckled tank car in that train testifies to the magnitude of those ‘buff’ forces - note that only 1 truck of that car derailed, though neither of the adjoining cars derailed:
Do they always occur in response to a service application?
Or do they sometimes occur spontaneously when no other braking event is occurring?
If a train is found to contain a kicker, is there any way to determine which car in the train is the kicker?
Is there ever an occurrance of one car with some type of brake valve defect that causes it to dump its air and dynamite the whole train when no service application is occurring?
Not always, but that is the normal occurrence.
Train lines leak, and sometimes, the pressure drop is just enough to set the kicker off, but most often the service reduction is the initial event.
You can find a kicker, but it depends on where you are, how long the train is, how much time you have.
While the engineer recharges the brakes, you walk to about the half-way point, and have him set the brakes.
You listen, and can hear the “emergency” application and the air rush towards you; it will start from the kicker and work out both ways, towards the front and rear of the train.
If the sound comes towards you from the rear of the train, the kicker is in the back half…start from scratch, have the engineer recharge the brakes while you make your way half way down the rear of the train, and start over…process of elimination will get you close enough to the kicker to finally hear it set off the brakes and you can isolate the car, which means you can sometime cut the brakes out on that car, but that also means you have to stop and set it out first chance, and on some roads it means you have to proceed to that point at restricted speed.
Well, the crew would certainly know that there had been an undesired emergency application (UDE) before the derailment, since they would know there had been an emergency application and would know that they had not initiated it. The question of whether the UDE “caused” the derailment would be for others.
Another way would be by inference or deduction after ruling out the other usual possible causes. For example, if the track is in good condition, with no signs of internal defects where the rails broke, and recent Sperry and geometry car runs found no exceptions. Also, no equipment defects found such as broken wheels near the front of the wreck or old axle cracks, etc. Finally, some positive evidence of excessive train forces, such as a buckled car still on the tracks, or a pulled drawbar from a car at the front portion of the train, etc. There are 2-day professional courses on derailment investigations, and/ or people with years of practical experience, that go into this in far more detail.
I remember a derailment that occured in Birminham in May of 1963, and the cause was immediately known. The Southern’s line into the Terminal Station crossed the main line of the L&N just east of the station, and the crossing was protected by a manual gate which was manned by the L&N. A Southern freight, bound for Northern Alabama, was approaching the crossing, and the L&N man suddenly threw the gate across the entrance to Terminal Station. The Southern engineer, instead of using the train brake, used the engine braks (I never heard why (I was passing through on the Peliican, bound for Bristol; Virginia). Even though the train was moving no faster than yard speed, several cars were derailed–blocking that entrance to the station. At that time there was track from North Birmingham to Woodlawn Jct., so the Pelican & the Seminole (on the CG) were not serious delayed.
Thanks for posting those reports. The following is quoted from the first link in a discussion of how slack action can cause a pressure drop in the trainline sufficient to dynamite the train:
"1.17 UDE Research
Although most UDEs occurred subsequent to a service brake application, the report also concluded that slack action (draft and buff forces), accompanying or in the absence of a service brake application, may cause short-duration bpp reductions, leading to UDEs.
During this testing, it was demonstrated that severe slack action alone can produce sharp bpp reductions of up to 2 psi. Laboratory work also showed that control valves could respond to slack-induced bpp reductions and initiate a UDE."
What I would like to know is how it is possible for slack action to affect the trainline pressure.
Glad hand gaskets can leak, if there is break or tear, even worn spots on the gasket, the slack action or bunching up the cars can cause the glad hands to rotate just enough to allow these small gasket defects to leak badly.
And on some cars with cushioned under frames, the train line and air hose ride on a carrier rod, which allows the hoses to move with the draft gear, if the attachment hangs up, stretching the train or slack running out can cause the glad hands to separate.
All that holds glad hands together is gravity, the tension created by the hoses, (they are stiff and retain the slightly curved shape you see) and the internal air pressure helps hold the two parts together.
I hear what you are saying, but it still leaves me wondering. I agree that if slack run-out can cause a trainline pressure drop it must be due to the slight physical disturbance of the air hoses. I can’t imagine any other way that run-out could affect trainline pressure.
I know the gaskets can seal so poorly in cold weather that it can pose continuous leakage to the point of being a problem. So, I can see that in cold weather when the hoses and gaskets are stiff, run-out might turn the glad hands slightly and disrupt the gasket seal enough to cause a momentary leak. And it would only take one hose connection to trigger the emergency application of one car, and then continue on to the whole train.
I can see the hoses actually parting in problems with a cushioned drawbar mounting, as you mention, but the reference in the report seems to confine the issue to a pressure loss with no hose parting. It refers to a brake pipe pressure loss of up to 2 psi, so that must be just a momentary leakage rather than a complete drop associated with hose parting.
I am curious because I have heard about air hose gasket problems in cold weather many, many times, but never heard of slack alone causing a pressure drop in the trainline until reading that report.
Isn’t it not the slack running out but running in? I mean if the engineer dumps the air the brakes are set car by car, one at a time, from from to back even thought it is emergency and that it is quick…thus the front of the train stops short and the cars behind, depending on speed, grade, curvature, etc., will keep coming into the stopped or stopping cars with noplace to go but off the track either to the side or up or telescoped. Dumping the air does not mean all cars or the whole train loses air at once, it is still a front to back action, but much quicker than normal controlled applications. At least that seems to stand to reason.
What you say is true, but that is not the point of the few prededing posts. The point of those posts is slack run-out causing a pressure drop in the trainline, which then dynamites the brakes. Look at the reference in blue the fifth post above this one.
Actually, in looking at it again, I see that they don’t specify run-out or run-in. They just refer to slack action causing brake pipe pressure to drop. I am mystified.
Can you explain how slack action can change the pressure in the trainline?
Slack action could do that by jerking the glad hands on the air hoses so that one or more could pull apart or the couplers themselves lose integrity and pull apart (there could be a jumping up and down of the cars so that the couplers seperate up and down; this is the reason for tight lock couplers, those with a “shelf” or ear at the bottom). In pull aparts we don’t often think in terms of virticle motion but horizontally along the line or plane of the train. I wonder, too, that if a mile long train has a difference say of 100 feet from bunched to stretched and a quick jerk would cause that 100 feet not to have pressure changing the train line pressure and setting brakes. I don’t know how quickly a bunching or stretching would have to occur to have such a effect, but it might be very quick and violent enough to set the brakes…
Since air in the train line acts like a fluid, might severe slack action cause a pressure wave to go thru the train line? A control valve that’s prone to dynamite might see a momentary drop in air pressure and think an emergency application is being made.
I do know that slack action can have an effect on glad hands. Usually it’s when the slack comes in. You’ll see the EOT drop a few pounds then come back up or maybe see the air flow indicator show that more air is flowing back to the train for a few moments. Doesn’t always initiate a UDE. Around my neck of the woods we call that problem having a “slip joint.”
I did have a train once that when into emergency 4 times, everytime the slack came in. The problem car was towards the rear and the emergency stop tended to pull the slack out and the air would come back. The problem car was an autorack, the entire train was autoracks. It was a very cold morning before sunrise when we had the problems. Once the sun was up and it warmed just a bit, I experienced drops in pressure on the rear (both from the EOT reading and engine Air Flow gauge) but no UDE. I told the outbound engineer about it and that trying to keep it stretched seemed to help. (I still had it go on me one time with the head end in power and air set to keep it stretched.) When they left, I rolled the train by. 8 cars from the rear was a car with a new air hose. I had learned previously that long drawbar cars have a special air hose with the glad hand angled differently. (I found this out when we took a bunch out to a car man. We had been given those kind for long drawbar cars but he needed regular ones.) The new hose on this car was a regular one. It’s not that they don’t work, but that they don’t always sit right. The slack coming in caused the hose to flex just
Isn’t the triple valve just a slug of metal with rings and grooves in it that sits in a close fitting cylinder? When the pressure changes on the brake pipe the slug moves due to the pressure differential with the other side of the slug. When pressure is applied in the brake pipe the slug moves such that the rings and grooves allow air from the pipe to be pushed into the air tank on the car and air in the brake cylinder to escape (releasing the brakes). When the pressure in the tank and the pipe are equal the slug is centered in the cylinder and no air moves. When the pressure in the brake pipe is reduced the slug moves the other way and the pressure in the tank is applied to the brake cylinder (applying the brakes).
If the slug is too loose in the triple valve cylinder or is maybe hung up on a burr or something that has kept it from actually centering, then a small jar to the car can cause that slug to move far enough to act as though the brake pipe had a large reduction in pressure, thus appling the brakes hard on that car. Then it might reset in position due to the brake pipe’s higher pressure (to re-pressurize the car’s tank) and that would be like a rapid reduction in brake pipe pressure and cause the other cars to set their brakes in a ripple effect down the pipe.
I am just surmizing based on my simpleton understanding of the basic triple valve.
I guess that must be what happens. That is, the slack rotates the glad hands. I can picture that if the gasket seal between glad hands were physically upset just a tiny bit, it might allow a leak to suddenly burst through, and that burst might last a second or two as the gaskets reset their new position relationship to each other.
I found a reference that says the free slack in each coupler is 1”, and the sprung slack at each drawbar is another 5”. So, that is 12” of potential slack at each joint.
Not only are you talking 50 feet in one hundred car train, but also the slack pulling out is more severe fhe further back from car one you go…the jerk action is trementous at the 75th thru 100th!
But we are talking about a pressure change inside of a closed system. The volume of that system can have nothing to do with train length changing due to slack.
But apparently, the closed system can leak as the distance between each car is changed due to slack.
I wondered how the severity of slack could have any effect. I assume the answer is: the greater the severity, the greater the slack distance between each car, and therefore the greater the potential to rotate the glad hands.