i think that a forum below kinda covered my question but i want it in a more simple form without all of the fluff i ws thinking that without slack the train, it could not move because it gives enough momentum in the first few inches of slack to get so many cars moving and if it was solid it would be trying to pull 6000 tons all at once. For example you cant eat a 16oz steak in one bite but if you eat it alittle at a time it is possible to eat the whole thing
Whoa - whitespace is your friend.
I may not be able to eat a whole 16 oz steak in one bite, but a lion probably wouldn’t have a problem doing so.
The analogy there is that you and I are steamers and early Geeps. The lion is an SD70MAC.
good point. good point.
…I really wonder about all of that…So much weight put behind a sourse of power and then power up to move it…If it can’t get it started {by itself, by any means}, can it keep it moving if it somehow is put in motion…?? Have to think about that.
The “power curve” or whatever they call it of a diesel is very different than a steam engine’s.
Steam gains power as it picks up speed, if a steam engine can start a train and get the whole thing to move, even at a crawl, it will probably be able to get it up to normal track speed with no problem - though it might take it several miles to get up to speed. Taking slack allows the steam engine to add one car at a time, by the time the caboose is moving, the engine should be able to continue to pull with no problem.
A diesel has all it’s power available right away, so has a much easier time starting a train…so wouldn’t have as much of a need to take slack the way a steam engine might.
Keep in mind too that by taking slack to start the train, you add to the risk of pulling a coupler on one of the cars in the rear part of the train.
Think of it in terms of a stick shift transmission. A steam locomotive needs to start in “high gear” whereas a diesel shifts to “low gear” for starting and up-shifts as the speed increases.
Trains move from a dead stop with the slack stretched out all the time.
how can you start out with slack stretched out if slack bunches up when you slow down
Because we stretch em out when we stop.
sorry i am kinda dumb in this category[:)] but why would you want to stretch them out??
For smoother stopping/starting, and to keep people from pulling pins while stopped. If the train is streched out, the pin can’t get pulled, and the train stays together. This is a big consideration in Chicago.
Theres alot of reasons, come up and make a nice smooth stop, easier to pull a train up “tight” against a signal or derail, piece of track your on makes for better train handling to stop and start that way…
yeah makes sense.
Is it also possible to uncouple the cars from accelerating too fast. because when i had gotten a cabride the engineer told me not to accelerate too fast or i would pull the cars apart. is this possible
“You may break a knuckle” is more like it. You may even break the drawbar/draft gear on a car, but most likely it will be a knuckle.
Slack control, or the lack thereof, is the cause for many a broken knuckle. Seasoned engineers will tell you that good slack control on a moving train comes with experience. Too much slack run-out can cause the train to break somewhere. Too much slack run-in could cause a derailment. Many times when a knuckle breaks it’s somewhere from the middle of the train foward, but this is not always the case. Wherever it happens one thing’s for certain… the conductor’s going to have to try to fix it and he/she won’t be happy about it. A good lecture, to put it nicely, should be expected sometime during the remainder of the ride.
On a stopped train slack control seem to require more common sense than experience. It has been my observation numerous times here in South Florida that engineers on long trains ease through the throttle positions, taking out all the slack in notch one. They then continue to accelerate slowly to about 5 mph before increasing the throttle position by an additional notch, etc. This is primarily due to the fact that the train is real long and real heavy and if you pull too hard you may break a knuckle or fry a traction motor.
The following video is a good example of what I’m describing. It’s of a 8900’ FEC Intermodal train pulled by two GP40-2s starting out from a dead stop: http://tinyurl.com/2wknos
Slack is a double edge sword. It is a product of the automatic coupler. It has been exploited as a benefit in starting trains, but it has always been a problem for train handling. The issue it poses to train handling is closely related to the issue of train brakes. There is a dramatic improvment to train brakes being tested today for possible universal application:
Is that so? I am pretty positive any conductor that trie
Max,
I’m referring to a junior engineer with very little road experience at the controls. Hardly anybody that a train’s conductor should be intimidated by for giving constructive criticism to. I know that if I had to fix something that a crew member of mine broke I would definitely have something to say about it, especially if it could’ve been prevented. In the event that the occurance was unavoidable I would have to cut him some slack…No pun intended.
I don’t know about how they do it in your neck of the woods, but in these parts the conductor is responsible for the train and calls all the shots.
l don’t think slack is required at all for pulling and it comes with drawbacks like rough rides. Even when coupling on to equipement, if it’s too smooth the pin won’t drop. This makes people think that rail shipping cannot be smooth, but in reality there are many coupler types that don’t need slack.
Shipping by rail should and could be a smooth ride, but because of standardizasion of couplers the rail industry has to live with a rough ride caused by loose slack. The Roadrailers are exemt from this and run smooth with 150 trailers.
So the roving, unpaid, utility brakeman can’t pull the pin and uncouple the train…is one signifigant reason!