Why don't engines have a continous throttle like a car, one which would have "infinite" settings instead of 8? Seems to me that if you could set the speed where you want it and use the brake less it would advantageous in the pocket book of the railroad.
I'm not usre , but I think the newer engines, have like a simple lever that you push forward, it'll go 47 or 33 mph, instead of set speeds. the nemwer engines also have a computer set in the dashboard/control desk that tells exactly what sepped, and I heard of some havinbg a GPS system to know where the destination is. I not sure, though some one knows, though
I've always thought that the speed of the train was not directly related to throttle position but more the result of time at a given throttle position. Combined with weight, grade, momentum etc - I would guess that it's quite difficult to get a train to hold a steady 33 mph for a long time. I know there are some engineers here. Maybe someone can fill us in?
The prime mover only generates electricity for the traction motors. The speed is regulated on a DC locomotive the same way you regulate it in on a model train, by adjusting the voltage, and like a streetcar controller there are only a limited number of resistance points. BUT, not only must the voltage be adjusted, but the RPM's of the prime mover, so you have a complicated "feedback" system further complicated by "transitioning" the traction motors from series to parallel circuitry as the voltage goes over a certain value. EMD started out with the 8 notch throttle and everyone else followed suit.
rsn48 , most of the time you cannot leave the throttle in one position and leave it , when you start to go down hill you don't have to use the brakes , usually , you can throttle back and control the speed of the train that way . Alot of train handling and speed control comes with experience on the territory that you operate on . I have gone 156 miles , my entire run WITHOUT setting the train brakes at all . In fact , I rarely even touch the train brakes until I am at the end of a run and then I set them up full service , then when the next Engineer gets on , he can release the brakes and his RDU will show that the rear car is released . I got of the point here a bit , but throttle 1-8 makes lifting a train easier and using throttle control can help you manage your speed better . Dynamic Brake also has 1-8 , having throttle 1-8 notches is NOT a inconvience at all . I always use Throttle Modulation and Dynamic Brake to control train speed and to stop the train . But to have a throttle with no notches would make train handling difficult IMO . For instance , if you had a gas pedal like throttle and you were lifting a train from a stand still , and you accidently pull out too much , your going to rip your train in half Throttles with notches is a safe guard from doing that , from taking too much power , usually lifting a train you go to 1 and when you can feel the weight starting to move , you increase to 2 then all the way out to 8 if the signal is green after you see the tail car is moving on your RDU [ 06 March 2001: Message edited by: Davecn5623 ]
Thanks, Dave, I felt like I was in the cab with you watching you control the train Good explanation of how you operate Most locomotives seem to have eight notches on the throttle, but did I read somewhere that some GE'S? had "half notches" at one time?
Alan , I could explain it better if I was there showing somebody , I am a hands on kind of guy , sometimes I feel like I can't get my point across thru this computer I have not yet seen these GE's with the half notch .
Dave, I remember reading somewhere (Trains maybe) someone describing the difficulty of getting a train over the crest of a hill. Too much or too little throttle can easily rip the train in half at the crest. What's the trick?
<BLOCKQUOTE>quote:</font><HR>Originally posted by Davecn5623: [B I have not yet seen these GE's with the half notch .[/B]<HR></BLOCKQUOTE> Matt tells me they were the U25B's
Originally posted by yankinoz: I remember reading somewhere (Trains maybe) someone describing the difficulty of getting a train over the crest of a hill. Too much or too little throttle can easily rip the train in half at the crest. What's the trick? I'm not Dave but maybe I can help out. As with everything, how you handle a crest depends on lots of variables, weight, power, train length, speed, severity of the grade etc. Generally, if you come over the top with a lot of throttle, the excess power pulling down hill plus the added weight of the cars already over the crest and coming downgrade can add up to more than a knuckle deeper in the train can stand. The trick is to ease off the throttle as more of the train comes over and starts downhill. Depending on the situation, you may need to have brakes set coming over the top or you may just hold it all back with dynamic as you get the whole thing on the down side. The danger of using too little throttle is that you could slow too much and stall before you get over the top. Or if you back off too fast and let the slack come in, the rear end may pause for a moment, then take off in the opposite direction from the head end. Trains going two ways at once don't usually stay in one chunk for long. This leads to unhappy conductors and uncomfortable sessions answering questions from official types. Hope that helps a little.
That helps out a lot - thanks Rule! I hadn't thought about the part of the train already over the crest pulling for you. Depending on the grades, there would be a point in the train that once it's over the crest, you don't even need a loco to pull the rest over. It does sound like a delicate balancing act! Do these new computerized engines help with these sorts of things?
Some early model EMD SW type switchers and many small industrial locos have thottles without notches. These control the diesel engine speed directly. The notches help in the more complex locos that operate over a variety of speeds and need to control electrical circuitry as well as engine RPM. The units without notches are normally not MU equipped either as that is done electrically and needs set values for each unit to operate at. The GE U25 has half notches to allow more electrical steps in the circuitry, but each half notch was electrical in nature, the RPMs changed only on the whole notches. Some electrics and gas turbine locos had 32 notches. The only modern equipment that I know of with no notches is the Amtrak Rohr turboliners in NY State. Their throttle controls a turbine powerplant directly.
Depending on the grades, there would be a point in the train that once it's over the crest, you don't even need a loco to pull the rest over. It does sound like a delicate balancing act! Do these new computerized engines help with these sorts of things?[/B][/QUOTE] Nope, not much. Some have a pointer on the speedo that predicts when you are accelerating or slowing down which helps to some extent but a lot of them don't work and it's usually just as easy to watch the old needle on the dial anyway. Knowing where you are and what's coming next is the best tool in the box.
This might be a better place to tell this than in "Tales From the Cab", since it sorta fits in here. I'll change a name or so to protect the teller, me. I had asked a friend how it was to pull really heavy loads up over his least favorite grade? As near as I can quote him, he described it like this to me: (he said,) "I'll see if I can clarify things about my least favorite grade just a tad. Saginaw Hill is a nasty little piece of work about 8 miles long that has humbled and terrified a list of engineers (myself included) that is both long and dignified. It's the one place on the dividion that remains a separate qualification to take loaded trains, and quite a few guys never did qualify over there because it is such a pain in the tush! The common wisdom is:"It's not IF you'll get into trouble on the hill, it's WHEN!" Knuckles, drawheads, stalls, and runnaways are the most frequent form of entertainment for the uninitiated. The main work in Itaska is a salt mine that ships loads up the hill and a power plant that gets coal loads down, so you're always fighting the hill one way or the other. From south to north you would normally be running empty salt hoppers or loaded coal, so your first test is to get up out of Seymore. No problem with empties, but with 19,000 tons of coal from a dead stop is a thrill! (You have to run around the train). It's upgrade all the way, with the worst of it right at the starting line. I got my knuckle about a mile into the pull after I thought I had it licked. No rest for the wicked. Anyway, you drag yourself along north for about 20 miles, usually wide open and wishing you could make track speed (25mph), then you get to the next event! You crest over the top and start into a 3 mile sag that makes the whole thing get really interesting. You can't hold the train back with dynamic alone as you start down, so the the best thing is to take out about 6 to 8lbs. of air on the train and hang on with the dynamic. As more of the train rolls up out of the sag at the other end and over the top onto the steepest part of the downhill, you take out a total of 10lbs. air and control the speed with throttle and dynamic the rest of the way. If everything behaves, you can just tool on down until the grade flattens out a bit about a mile from the bottom, then knock off the air and finish the job with the dynamics. It rarely goes quite like that. The sag is usually where the trouble starts when you make your first mistake, and take out too much air and stall or break the train trying to pull it out the other end. Make your second mistake and knock the brakes off and you're in for a shock! I was with a guy who did this by accident and the accelleration pushed me right back in the seat! I would never have believed it was possible for that much weight to move that fast, but it took off like it had afterburners! Then its just Panic Time! You can dump the train, but sometimes it will go 2 miles after you go into emergency. Then your poor conductor has to tie the whole mess down with about 70 hand brakes while you charge up the train and take another crack at it. If you try to hurry the process, away you go again, but this time you have no brakes at all because you shot all your air going into emergency! You can also be brave (or stupid) and try to ride it out. There is a sharp left and two sharp rights down at the bottom. If you are lucky you'll derail at the left, and only take out one house and a highway bridge. The fastest I ever heard of coming down was 57mph, and no, they didn't make it. If you do get around the left, the next is a right that has a trailer park right on the apex of that curve and down a bank, so you'd wipe out about half of that. The last right is by far the sharpest and you will not make this one at any speed at all. They'll be mining coal and locomotives out of that swamp where you parked them for a good ten years. Once you do manage to get down off the hill, you still have a city to go through, and a plant that is all ups and downs but at least those sections wont kill you. Now if your headed south from Itaska with 40 loads of salt or 130 empty coal hoppers, you have another set of problems. We usually try to have 12 to 16,000 horse power up front for the salt and 7 to 10,000 horses for the hoppers, but it doesn't work out that way very often. Saginaw Hill is sneaky, it lets you get started up until you're committed and feeling confident them WHAM! It bites and you're stuck! The farther up you go the steeper it gets, and right at the top are the Heartbreakers, a set of S curves that bind the wheels and a 2% that can stall you within sight of the crest. That's where I was crawling and bucking at 1,300 amps the other day! A side note here: A diesel's actual power output is measured in amps (or foot/lbs, for AC units), and 3 or 400 amps is pretty average power. Anything above 800 amps has my undivided attention, and 1,200 amps or higher is in the red zone where the motors are cooking, the flanges are screaming, you're burning fossil fuel in gallons per second, you've got all the sand buttons on and one slip or hiccup will earn you a lunge and a broken train. I don't know how to figure the math, but 2 units putting out 1,300 amps at 600 volts DC each, has got to be substantial!! I do know that I NEVER take my hand off the throttle nor my eyes off the gauges when we're down to the nitty-gritty like that! If it did break, the head end would shoot foreward like a missile until the emergency brakes caught up with you. Like I said, it always gets my undivided attention! Probably by now you get the idea I have a lot of respect for that old hill. I've heard some of the older heads tell some awful tales about it, and I'm inclined to believe 'em! Most kidding stops when the head end drops over that cliff and 19,000 tons of coal starts to shove relentlessly for all it's worth! You ever have that "Oh my Gawd" feeling when you realize things are starting to get out of hand? I always hated that!"
<BLOCKQUOTE>quote:</font><HR>Originally posted by yankinoz: Dave, I remember reading somewhere (Trains maybe) someone describing the difficulty of getting a train over the crest of a hill. Too much or too little throttle can easily rip the train in half at the crest. What's the trick?<HR></BLOCKQUOTE> Hey Rob . The territory I operate on is pretty flat . We have a hill or two but nothing major . All I do is make sure I never let up on the power when I am going up a steep hill or a crest , if you do your stalled . One thing I have noticed is that at the bottom of every grade or hill there is always water , river , stream , swamp ,ect.. When you are going downhill you have to be careful , because when your head end is starting uphill again your tail end is at the bottom or getting close . That can cause serious run in and run out and cause you to come apart . To avoid that you want to throttle out before the tail end runs into you or your head end . I may have not answered your question but usually going over a crest is not a problem unless the knuckles are weak on some boxcars
Thanks guys, the credit goes to the engineer I told it for. You other engineers, or whoever has a tale from real railroading, are welcome to post it in the Forum, "Tales From the Cab" where real life stories told from the cab by those who lived it, or know about it, let others know what it can be like real steam and diesel engine cabs. I'll post another story over there. Come on over and tell us yours, some will roll your socks down!
