I have a question for forumites who are or were actually trained & experienced engineers. If a train, especially a train exceeding the speed limit, is going around a curve, will applying the brakes in full emergency tend to cause a derailment. I ask this because I know, from having been on Amtrak trains that went into emergency, that before moving there must be an on-gorund inspection, which leads me to think such braking can itself cause a derailment.
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That inspection is to check for any foreign objects that may have caused the BIE (Brakes in Emergency), along the roadbed.
Richie
Ritchie, one occasion was caused when the Acela engineer applied emergency due to seeing kids on the track ahread. The other was applied by an Auto-Train conductor when she couldn't raise or hear the engineer on the radio. So foreign objects wouldn't have been an issue.
Ritchie, one occasion was caused when the Acela engineer applied emergency due to seeing kids on the track ahread. The other was applied by an Auto-Train conductor when she couldn't raise or hear the engineer on the radio. So foreign objects wouldn't have been an issue.
Maybe not but, I believe it is standard Amtrak practice to inspect the whole train after an emergency application of any kind.
Hot Water, what's your answer to my initail question? As I recall, you were an engineer.
Hot Water, what's your answer to my initail question? As I recall, you were an engineer.
Sorry, steam only. However, I must admit that in all my years in the railroad industry I have never head of any limitations/restrictions concerning application of brakes in curves.
Are the physics affecting steam locos that much different from diesels?
Yes after an emergency brake application on passenger trains , each car must be inspected to see if the brakes are released and a pull by to check for skidded wheels. I suppose any time a emergency brake application takes place there's always a slight chance of a derailment. Probably not so much on a passenger train but more likely on a big freight. Even then it doesn't happen very often. I'm old school and the guys I worked with would give a minimum brake application before a curve just to settle things down a bit before entering the curve.
Are the physics affecting steam locos that much different from diesels?
Probably yes, since you better not apply the brakes on a steam locomotive while braking the train. Remember the tires are heat-shrunk onto the wheel centers. Thus, with asteam locomotive power braking was the order of the day. Now, with blended-dynamic braking, things are much different on passenger trains.
Are the physics affecting steam locos that much different from diesels?
Probably yes, since you better not apply the brakes on a steam locomotive while braking the train. Remember the tires are heat-shrunk onto the wheel centers. Thus, with asteam locomotive power braking was the order of the day. Now, with blended-dynamic braking, things are much different on passenger trains.
Thank you for that explanation. It makes complete sense.
As an aside, I used to instruct at a race driving school in a former life, and braking in the turn was a huge no-no unless you wished to visit the outer fence, or swap ends.
Of course, physics are involved. Not being a physicist, I could not explain what I think would be different effect of braking of a tracked/guided object (train) versus a free-wheeling object (race car) with regards to the momentum and energy required to break adhesion and prevent the object from turning.
Are the physics affecting steam locos that much different from diesels?
Probably yes, since you better not apply the brakes on a steam locomotive while braking the train. Remember the tires are heat-shrunk onto the wheel centers. Thus, with asteam locomotive power braking was the order of the day. Now, with blended-dynamic braking, things are much different on passenger trains.
Thank you for that explanation. It makes complete sense.
As an aside, I used to instruct at a race driving school in a former life, and braking in the turn was a huge no-no unless you wished to visit the outer fence, or swap ends.
Of course, physics are involved. Not being a physicist, I could not explain what I think would be different effect of braking of a tracked/guided object (train) versus a free-wheeling object (race car) with regards to the momentum and energy required to break adhesion and prevent the object from turning.
Yes, Mr Rocks, you are generally correct about braking in curves. Why? Well it is fairly obvious that if there is a speed limit for the curve in question, the logical thing to do is to have your speed down to that limit prior to entering the curve, at least that is the way it works on the railroad.
Gotcha! I am just curious if, say given a train and car are identical weight and on identical degreed curves, would a train be able to withstand a higher speed on a curve than car on the same curve, with no track
I know, we're delving way of course now.
In freight service, a former co-worker found himself confronted with that situation and what he did was open the throttle and pile on the train brakes. The power (engine) and brakes (cars) combined, stretched the train out and they went around the curves and exited the other side. Possibly with dirtied pants! Remember, the engine brakes get bailed off so you don't have to worry about any heat problems.
You don't want to put the train in emergency unless absolutely necessary and unbalance the cars in the train. It really comes down to a split second decision and you would be surprised at how fast the mind works when making that decision!
One other thing, there is a calculated turning over speed. If that speed is exceeded, the train is going to derail no matter what you do.
Thank you Jim!
RJR, I was a conductor for NS for some years and it would depend how much over the speed limit one was going. Have you not been watching the news lately about the derailment in Philly? Going just a few mph over probably would not cause a derailment. I have been on several trains that went into emergency without derailing.
As per NS, if a train goes into emergency, the conductor must walk the train to make sure that none of the cars did in fact jump the track. At least that's how it was when I was there.
Rick
Rick, yes I've been watching, but the question occurred to me if there would have been a better chance of getting through the curve if he hadn't put the train into emergency.
Hot Water, can you explain to me "you better not apply the brakes on a steam locomotive while braking the train. Remember the tires are heat-shrunk onto the wheel centers." I read you as saying that you don't want both train brakes and loco brakes on at thew same time or the loco wheels will overheat?????
I have a question for forumites who are or were actually trained & experienced engineers. If a train, especially a train exceeding the speed limit, is going around a curve, will applying the brakes in full emergency tend to cause a derailment.
A 7 car passenger train, "NO". An 8, 10, 12, up to 20+ thousand ton freight "YES". As usual with railroading, there is no short yes or no anwser. There are many factors that must be considered when initiating an Emergency application of the air brakes from the head end of the train. Most important is the train make up, the position of the loads and empties and total trailing tonnage of the train along with the physical characteristics (uphill, downhill, curves) of the track .
A. Keep in mind that the same braking effort is applied to an empty 30 ton car as is applied to a loaded 130 ton car. Therefore retarding force (braking effort) is more quickly generated on empty cars than on loads.
B. When an Emergency Air Brake application initiated by the engineer, the brakes are applied from front to rear, not simultaneously, with the application traveling through the train at around 930 feet per second. When you consider a freight train may be in excess of 7,500 feet long (some longer) it could be over 8 seconds after the brakes start applying on the head end for the brakes to start applying on the rear.
C. Just as with anything else, the mometum of a heavier object will push the lighter object out of the way, if you have empties positioned on the head end of the train (lighter cars) and loads behind (heaver cars), it is entirely possible for the buff forces (forward momentum) of the loads to buckle or push the empties off the track, sometimes even on perfectly tangent (straight) track.
Hope this helps.
Rick, yes I've been watching, but the question occurred to me if there would have been a better chance of getting through the curve if he hadn't put the train into emergency.
Hot Water, can you explain to me "you better not apply the brakes on a steam locomotive while braking the train. Remember the tires are heat-shrunk onto the wheel centers." I read you as saying that you don't want both train brakes and loco brakes on at thew same time or the loco wheels will overheat?????
As I already stated the tires are heat shrunk onto the driver centers (wheels). Thus, if heat is reapplied to the tire/tires,through braking friction from the brake shoes, the tires expand, and "fall off" the wheel. The engine brakes (independent brakes) on a steam locomotive are only used when the locomotive is running light, i.e. not coupled to and cars with air brakes.
Thanks, hot water, for the explanation. And thanks to thd others who have replied to my question.
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