How does the engineer of a freight train control the slack if the train stops on an upgrade? Downgrade? No grade (if there is such a thing)?
On a recent trip from El Paso to Tuscon on the Sunset Limited, a Texas Eagle passenger on the through sleeper told me that he did not like to ride in the last car because of the whipping effect created by the slack running in and out.
I am under the impression that Amtrak’s Superliner cars, at least, have practically no slack action because of the lock tight couplers. Am I correct?
Yes; tightlock couplers have very little, if any slack. Did he mean a side-to-side motion–which would not be caused by slack action? I do not recall a side-to-side motion the times that I have ridden in the last car on a train that came because it was the last car (the only adverse motion I do recall from that position of the car was the up-and-down motion of the foot end my berth in a roomette on the rear of the L&N’s Pan American between Birmingham and Montgomery–which ended when the Atlanta-New Orleans sleeper was added in Montgomery.
The only adverse side-to-side motion I recall comes from the rocking caused by track that needs surfacing (the worst ever in my memory came last year when the California Zephyr was detoured across Wyoming and we had to enter Denver over the Belt Line–which seriously needed surfacing. I did not remember such rocking the year before when we were detoured going west.
I would suppose that if it’s a longer train, there will still be a little slack - and if you’re sensitive to it, you’ll probably notice.
If we assume just a half inch of slack between cars, that’s still ~5" for a 10 car train. Not much, but it could be enough…
The side-to-side thing might have some validity for the last car. The rest of the cars have at least one car on either side (end) that may dampen such motion. So there might be a little “whip” at the tail end of the end car.
And to think, in the glory days of passenger rail, the Observation Car, on the rear of the train, was one of the featured cars on the train. From my times riding a multitude of passenger trains, I have never noticed any perceptible slack action. A little stretch braking steadies the slack; of course now a days stretch braking is viewed as a waste of fuel.
He said that he could notice the slack running in and out in the back car. He also said that the back car sways from side to side more than the other cars.
I have ridden in the last car of the Pacific Surfliners from LAX to San Diego and back numerous times. Most of the Surfliners have six cars. I never noticed any slack or swaying, other than perhaps over a bit of rough track. But then I usually have my nose buried in a book, so I may not have been aware of it.
If there was slack action on a passenger train, I think I would have experienced it on a twenty eight car Canadian train in the Park car and there was none. However, I do notice something like slack action on the Metra commuter trains when the engineer transitions from power to braking and the cars do a small jerk.
The mechanics of the ‘tight-lok’ coupling system is a definite plus that adds much to the ride in a passenger train, possibly a consideraton might also be made to the intra-car diaphragm system (?) which might put some seperation between the cars of the train, and cushion some of the ‘slack’ action ?
The biggest help for improving the ‘ride’ of the passengers, I think, isx the individual skill of the Engineer at the controls. Their knowledge of the track, terrain, and handling is critical for the comfort of the passengers; not to mention that their individual skill set is constantly on display.
Any passenger at any time can complain to the railroad management about a ride. A poor ride could generate a flurry of derogatory e-mails within a short time of the incident. Possibly, at the end of the trip, a compliment/comment (?) or two could also be sent to that same management about the trip.
I live adjacent to a secondary main line, wigth a rising grade from West to East. I can tell you the larger number of engineers do a remarkable job of train handling, they pass by with barely any notice…and then you have the occasonal happening ( Engineer in training(?) or maybe very tired(?) whose stop sounds like the whole train is being put on the ground, or every knuckle is being pulled apart)
Free slack is the lost motion in the couplers, knuckles, etc.
Then there is the slack due to compression and expansion of the draft gear. The couplers are not rigidly pinned to the car underframe, they’re connected by a big spring (okay, not really a spring, usually rubber pads…). There is a lot more slack action from draft gear motion than there is from free slack.
I’ve handled a few Amtrak detour moves. Our crew change point going east is at a street crossing. The first time handling a detour move, I started the train real slow to allow the crossing signals and gates to activate. The Amtrak conductor radioed to me that I could just pull on them once we started moving. That I didn’t have to worry about pulling the slack out of the train like you would with a freight train.
We made one stop that trip to change Amtrak engineers (both of whom rode back in the train) near another street crossing. Starting up I again had to go slow until the crossing was protected and again the Amtrak conductor said not to worry about any slack.
When detouring, we have a pilot engine (for cab signals) and use the freight setting for the automatic air brake. Even though we don’t have graduated release or blended braking, they are still fun to run.
This conversation reminds me of something that happened in the late 1980’s or early 1990’s.
The late Thomas Dressler, respected author, N&W engineer, and N&W historian, rode the Auto Train as a passenger and wrote a letter to Amtrak President W. Graham Claytor to express his thanks to the crew for a good trip. He specifically cited the engineers’ excellent train handling in his letter. It’s the only time I ever heard of a passenger saying anything like that. It’s easy to take it all for granted; but if you’re used to handling long Manifests and coal trains, as Mr. Dressler was, then you know.
Mr. Claytor made sure the employees saw copies of that letter.
I’ve seen that done with Diesels, too, back in the day of “friction” bearings. The logic was the same, though - start just one car at a time instead of the entire train.
There has been a couple good articles over the years on how the crews run the Auto Train. They power brake it to keep the slack tight and from running out, mainly because of the size of the train and the autorack cars at the rear end. I have ridden it a few times and always had a great ride. Those are talented engineers
I appreciate the answers so far, but what I really want to know is how an engineer deals with the slack on a freight train that stops on an upgrade vs. a downgrade vs. a flat profile. Is there any difference?
If possible, my guess since I am not an engineer, when stopping on an upgrade, the engineer would want to run the slack in so that he or she could use it to help start the train? Is this correct?
Can the engineer apply the locomotive brakes independently of the car brakes? If the answer is yes, presumably then he or she could apply the locomotive brakes more robustly than the car brakes when stopping on an upgrade, thereby allowing the slack to run in? Is this correct?
There’s a huge difference. If you are stopped on an uphill grade there are many factors. Train tonnage, curve radius, the gradient, how much horsepower you have, are there pusher engines, etc. If the train is starting uphill normally, then the engineer may release the train brakes, hold it with the independent brake and carefully put enough power into it to start gradually get the train moving without slipping. That could cause a separation in the train by a broken knuckle or worse a pulled drawbar. Either way you’re going into emergency and now more problems to deal with. Like a trainmaster or roadforeman to say the least. If you had helper units, then you have the slack coming into you a little as you get going . Big difference. Downhill is a whole different animal. You might stop with a combination of dynamics and air. Starting up depending on the tonnage, the independent could hold you and a train release and slowly release the independent to start you going and back into your dynamic brakes blending it with your train brakes. Small releases are the key so you keep going and don’t have to stop again on the hill or use up all your air so you only have an emergency application. Bottom line is this is someone that needs to know what they are doing, experience and a good teacher that gave them pointers. Plus a feel for each train you run, they are all a little different.
When stopping on an upgrade the slack would normally be stretched out. That’s the way you want it. Taking slack to start the train is normally not needed with diesels. (I’ve only had to do it once because we stalled on the ruling grade when a trailing unit shut down. We were able to get it running and my engineer had me take a little slack to help start us.) Diesels can put out high tractive effort when starting, steam engines develope it at higher speeds. Hence, the need to start the train one car at a time.
With the slack in on an uphill grade, when you release the air brakes you could have the rear end start to roll back before it gets started. Depending on the type of train, that alone could snap a knuckle. Add into it the shock when the part of the train is moving forward meets the part rolling backwards and that could break the train in two.
Even starting a heavy train that is stretched out can be problematic. You need to use higher throttle positions, thus giving higher tractive effort. Should the locomotives momentarily slip it could allow just enough slack to run in and snap a knuckle when it starts to grab again.
Down grade, using dynamic braking, the slack will be bunched up. Using the automatic air brake for the stop won’t stretch the slack out. When starting, just release the air and let gravity help you get moving. Use the engine brakes to keep them (engines) from rolling out to fast until you can go into dynamics or power if needed.
Making a stop on a level portion, it depends on the train. Some trains, those with a lot of cushioned or long travel draft gear, I would rather keep the slack stretched out. Others I’ll use dynamics more approaching the stop, letting the slack bunch up. Just remember the condition of your train when you start again. At crew changes we usually let the outbound engineer kn
When the ‘wrong end’ happens, the end of the train with th operating locomotives have no means of coupling to the car that has ‘lost’ the wrong end. On a Eastbound train if the East end of a car has it’s coupling pulled out of the car - that is the wrong end. That car can now only be handled with engines on the West end of the train or cut of cars.
Only other potential band aid, is for the Car Dept to show up with chain(s) that can be affixed to the East end of the bad order so it can be handled to a set off location.
Jeff, I am sure that you are aware that I am a dinosaur who knows what the controls for a diesel engine used to look like–throttle, reverser, train brake, and engine brake (I was going to write independent or, even, straight air brake, but feared that that would confuse some who are new to the art of running an engine). With the changes in controls, I assume that you still have the engine brake and the ability to bail the engine brake off when it necessary to do so when using the train brake; I am wondering if this is done in the same manner as it was formerly. My only experience in running an engine consisted in running a light engine around a wye; I do not remember if I used the engine brake or train brake when I had to stop (the last time was about 42 or more years ago).