Can it be that all these people (except Ed) have forgotten about all the buff compression springs in the draft gears, which are compressed to some degree while the shove is going on, but that provide mutual recoil between cars ... all the cars in the cut ... when the locomotive decelerates?
Ulrich Maybe. I'm pretty sure I saw them accelerate.. but who knows, maybe my mind was playing tricks on me.
Maybe. I'm pretty sure I saw them accelerate.. but who knows, maybe my mind was playing tricks on me.
Watch 'Your Bleeped Up Mind' on History or Discover Channel's - to understand how really bleeped up our minds are in the way they work and 'fill in the blanks'.
Never too old to have a happy childhood!
Ulrich Acceleration. What if I drive my car at 90 mph and rear-end yours at a red light? Your car will definitely accelerate, I assure you of that. My car will lose some of its momentum in the process (not that it would matter much to anyone inside). Would not the same effect apply for a locomotive bumping some rail cars?
Acceleration. What if I drive my car at 90 mph and rear-end yours at a red light? Your car will definitely accelerate, I assure you of that. My car will lose some of its momentum in the process (not that it would matter much to anyone inside). Would not the same effect apply for a locomotive bumping some rail cars?
Thank you for offering me another opportunity to say what I and others have said already, just slightly rephrased. Yes, the other car will accelerate, but no more than 90mph minus whatever energy's lost in the collision, minus the difference between your car's and the other car's masses, minus friction. The other car will NEVER accelerate more than 90mph, just as the railroad cars cut free from a trailing locomotive will never accelerate as that locomotive slows down.
Patrick Boylan
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Overmod...the buff compression springs in the draft gears...
That would be those "outside forces" at work...
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...
"Can it be that all these people (except Ed) have forgotten about all the buff compression springs in the draft gears, which are compressed to some degree while the shove is going on, but that provide mutual recoil between cars"
Sorry, but that's not how draft gear works. Draft gears are designed to dissipate impact energy by first compressing (assuming forces in buff) and then slowly expanding back to normal, with retarding force generated by friction between rubber and metal elements (for conventional draft gear), or by hydraulic fluid forced through a small orifice (for hydraulic end-of-car cushioning units). This is the same principle used on automotive "shock absorbers" (more properly described as shock dampers). Any system with springs will oscillate wildly when perturbed unless some form of damping is provided. If you've ever had a vehicle with "bad shocks" that bounces you up and down repeatedly after hitting a bump you've encountered a perfect example of this.
So, a cut of cars will run in or run out depending on whether they are pushed or pulled, but they won't keep going back and forth like a weight suspended by a spring.
Kurt Hayek
And if you really want a wild ride - flat switch a cut that has a number of loaded tank cars in it! Can you say slosh slack!
BaltACD And if you really want a wild ride - flat switch a cut that has a number of loaded tank cars in it! Can you say slosh slack!
When I was training (no pun intended) at Beverly Yard, one of the yard foreman would use the sloshing of tank cars to pin them off when switching. Beverly is downhill, west to east. Most switching was done from the west end.
When cutting off tank car(s), he would bring the move to a stop. The slack ran out, but the slosh would bring the slack back in enough to pull the pin. The sloshing then would cause the car(s) to move away from the rest of the cut and down the yard track. I can't remember if it worked for all the tracks (north side of the mains) or just the first three or four tracks. It seems we were up around yard #1 switch when we did this.
I don't know if the other foremen back then, or now, used this trick. Maybe some of our Cedar Rapids area friends might be able to check it out some nice afternoon.
Jeff
Thanks for that story, Jeff. I was very aware of the sloshing action of tank cars. You don't want to get too close to either end of a string of those cars until you are certain they have come to a complete rest. But I had never heard of it being used to advantage.
John
An "up" train (from London) would approach a rural station at a fairly high speed. Brakes would be applied for a second or so and a brakeman on the last coach on the train would uncouple it. The train would then accelerate; allowing the coach to drift into the station where it would be shunted onto the arrival track. And, yes, this was apparently done with passengers aboard.
ChuckAllen, TX
Chuck is right about slip coaches. Passengers were aboard each coach since the concept allowed an express train to serve selected intermediate stops without making stops. The brakeman aboard the slip coach brought the car to a stop using only the hand brake.
sandiego "Can it be that all these people (except Ed) have forgotten about all the buff compression springs in the draft gears, which are compressed to some degree while the shove is going on, but that provide mutual recoil between cars" Sorry, but that's not how draft gear works. Draft gears are designed to dissipate impact energy by first compressing (assuming forces in buff) and then slowly expanding back to normal, with retarding force generated by friction between rubber and metal elements (for conventional draft gear), or by hydraulic fluid forced through a small orifice (for hydraulic end-of-car cushioning units). This is the same principle used on automotive "shock absorbers" (more properly described as shock dampers). Any system with springs will oscillate wildly when perturbed unless some form of damping is provided. If you've ever had a vehicle with "bad shocks" that bounces you up and down repeatedly after hitting a bump you've encountered a perfect example of this. So, a cut of cars will run in or run out depending on whether they are pushed or pulled, but they won't keep going back and forth like a weight suspended by a spring.
You are both right. Modern draft gear uses rubber pads, not springs. That's true. But the rubber pads are really just springs with a lot of hysteresis. The are capable of storing and releasing energy.
Hydraulic end of car cushioning is a different animal.
-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/)
sandiego "Can it be that all these people (except Ed) have forgotten about all the buff compression springs in the draft gears, which are compressed to some degree while the shove is going on, but that provide mutual recoil between cars" Sorry, but that's not how draft gear works. Draft gears are designed to dissipate impact energy by first compressing (assuming forces in buff) and then slowly expanding back to normal, with retarding force generated by friction between rubber and metal elements (for conventional draft gear), or by hydraulic fluid forced through a small orifice (for hydraulic end-of-car cushioning units). This is the same principle used on automotive "shock absorbers" (more properly described as shock dampers). Any system with springs will oscillate wildly when perturbed unless some form of damping is provided. If you've ever had a vehicle with "bad shocks" that bounces you up and down repeatedly after hitting a bump you've encountered a perfect example of this. So, a cut of cars will run in or run out depending on whether they are pushed or pulled, but they won't keep going back and forth like a weight suspended by a spring. Kurt Hayek
I still remember riding cabooses and I know for a fact that cushioned cars stopped bunched will accelerate themselves when the brakes release and the cushions decompress. Even with the head end stopped the rear will get going pretty good even on flat track. It's really quite a hit and you can't let your guard down until the slack settles.
I think overmod is right, I have some old bruises to prove it.
Randy
If your car bumps into another in front, the acceleration of that car in front will only occur during the period the two cars are in contact and your car is thus applying force to that car. Once your car slows down enough so that the car in front moves away from your car, no further acceleration will take place and that car will also begin slowing down, with whatever rate its conditions impose on it.
NOTHING ACCELERATED WITHOUT A FORCE BEING APPLIED
In a recent "The Railway" magazine, a British publication, there was an extensive article about slip coaches and how it was done. Seemed to be a common practice. Don't know if it was done anywhere else.
cefinkjrThen there were the British "slip coaches" described by the late John Armstrong several years ago. An "up" train (from London) would approach a rural station at a fairly high speed. Brakes would be applied for a second or so and a brakeman on the last coach on the train would uncouple it. The train would then accelerate; allowing the coach to drift into the station where it would be shunted onto the arrival track. And, yes, this was apparently done with passengers aboard.
That sounds like a drop.
I have wondered how the cars were taken back to London; I doubt it was on express trains.
Johnny
I am wondering what sort of hand brake test was performed before the drop to ensure that the brakeman could actually stop the car at the station - who was handling station switches?
BaltACD cefinkjrThen there were the British "slip coaches" described by the late John Armstrong several years ago. An "up" train (from London) would approach a rural station at a fairly high speed. Brakes would be applied for a second or so and a brakeman on the last coach on the train would uncouple it. The train would then accelerate; allowing the coach to drift into the station where it would be shunted onto the arrival track. And, yes, this was apparently done with passengers aboard. I am wondering what sort of hand brake test was performed before the drop to ensure that the brakeman could actually stop the car at the station - who was handling station switches?
Probably pre-Beeching era or earlier, when the British system had a far bigger labor force to check things and all stations were manned, often with a staff of 2-4 people.
C&NW, CA&E, MILW, CGW and IC fan
Last coach was probably filled with third class passengers...back then if a few of them got banged up in transit it wasn't that big of a deal.
I wonder how fast they were going when the pin was pulled. I assume they would have slowed way down from passenger train speed; maybe down to 15 mph or so.
EuclidThat sounds like a drop.
Yes, just different terminology for the same thing.
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