dehusman gregc doesn't this mean you either want the head end consist pulling the entire train or the trail end consist pushing the entire train? Not if you have multiple powered consists. The whole idea of helpers or DP is to not have the head end consist doing all the work.
gregc doesn't this mean you either want the head end consist pulling the entire train or the trail end consist pushing the entire train?
Not if you have multiple powered consists. The whole idea of helpers or DP is to not have the head end consist doing all the work.
maybe there's a simple explanation of how this happens that doesn't require a computer either. (it would be nice to hear this explained by someone experienced).
presumably if both lead and trailing consist have the same # of engines and are at ~equal power (i.e. same notch) they provide the ~same tractive effort. but the acceleration each provides will depend on load (# cars).
presumably if "~all" the couplers are slack, the lead consist is pulling "~all" the train. the trailing consist is generating that same force but with little load, so it accelerates faster, bunching up couplers near the tail end of the train, increasing its load.
as more of the load is taken up by the trailing consist, it accelerates less and conversely, as fewer car are pulled by the lead consist, it accelerates more, changing the # of cars pull/pushed.
at some point, an apprpriate # of cars are pulled by the lead consist and pushed by the trailing consist such that their accelerations are ~equal and they both maintain the same speed or increase/decrease speed at the same ~rate.
the # of cars pulled/push changes as the situation changes whenever the load on one engine shifts.
the lead consist of a train cresting a grade will start to accelerate and pick up more of the load as more cars crest the grade. the trailing consist will accelerate as its load is reduced. the "balance" changes constantly as the train crests the grade and will reestablish itself once the train is on level grade. a similar rebalancing occured when the grade changed
this balance, # of cars pull/pushed is maintained by physics. no computers required
greg - Philadelphia & Reading / Reading
LastspikemikeAre there advantages to coupling the two trains together?
besides, as the video said, there's fewer engineers, wouldn't separate trains be required to follow signals, need to be at least a block apart and not interfere with other trains. in other words, wouldn't seprate trains be extras? isn't a single long train more efficient?
There have been many discussions on the 1:1 forums and blogs about automated train operation, and systems like Trip Optimizer and Leader that attempt to do so. Suffice it to say that long North American freight trains are proving difficult to automate, in large part because the computers do not yet understand slack as well as a good engineer. I've also yet to see Trip Op get out and manually line frozen switches, or change the knuckle it just broke.
It does matter where you put the remote, and how many remotes you have, this will vary from train to train. As an example, a 200 car 30,000 ton loaded unit train requires 3 AC locomotives on our mainline. They are far easier to run when built 1x1x1 compared to 2x1x0.
They had also tried running such trains 2x0x1, but this led to some broken knuckles when cresting hills if you didn't put the fence up and throttle down the lead consist, as the front of the train would be accelerating downhill while the rear was still coming up.
Greetings from Alberta
-an Articulate Malcontent
Lastspikemike gregc Lastspikemike Are there advantages to coupling the two trains together? besides, as the video said, there's fewer engineers, wouldn't separate trains be required to follow signals, need to be at least a block apart and not interfere with other trains. in other words, wouldn't seprate trains be extras? isn't a single long train more efficient? In times past sure. But nowadays it is childsplay to automate a locomotive and current MU setups must in fact do so. I raise the points for two reasons: does current MU technology actually make the engineer obsolete or could easily do so? Is the dynamic behaviour of a MU hauled train mayerially different whether the locomotives are all at the head end or split mid train or even end train? If the two sets of locomotives could each haul half the train as a separate train and automation can allow the trailing train to run the same track section and signalling area consecutively, very close behind the lead train, then why bother coupling the two trains? Indeed, what's to stop the railroads from essentially running nose to tail with many trains in succession all protected by smart cruise control already available for individual passenger automobiles and tested for transport truck convoy setups? Docklands Light Railway (DLR) part of London's underground system, although in reality, an elevated system has run fully automated now for a very long time, just firvexsmple of what was already feasible years ago. Real underground trains run very close together under some sort of computerized safety system, although each train has a driver at least nominally in control. It seems to me that the discussion about whether and where in the train the loads are taken up begs the question of whether MU is really two trains coupled because railroads are required to have at least "one engineer" nominally in control of the entire train or for some other reason. It is correct that the current state of technology would easily facilitate one engineer controlling multiple separate trains from one locomotive. Coupling is not necessary for control any longer.
gregc Lastspikemike Are there advantages to coupling the two trains together? besides, as the video said, there's fewer engineers, wouldn't separate trains be required to follow signals, need to be at least a block apart and not interfere with other trains. in other words, wouldn't seprate trains be extras? isn't a single long train more efficient?
Lastspikemike Are there advantages to coupling the two trains together?
In times past sure. But nowadays it is childsplay to automate a locomotive and current MU setups must in fact do so.
I raise the points for two reasons: does current MU technology actually make the engineer obsolete or could easily do so?
Is the dynamic behaviour of a MU hauled train mayerially different whether the locomotives are all at the head end or split mid train or even end train?
If the two sets of locomotives could each haul half the train as a separate train and automation can allow the trailing train to run the same track section and signalling area consecutively, very close behind the lead train, then why bother coupling the two trains? Indeed, what's to stop the railroads from essentially running nose to tail with many trains in succession all protected by smart cruise control already available for individual passenger automobiles and tested for transport truck convoy setups?
Docklands Light Railway (DLR) part of London's underground system, although in reality, an elevated system has run fully automated now for a very long time, just firvexsmple of what was already feasible years ago. Real underground trains run very close together under some sort of computerized safety system, although each train has a driver at least nominally in control.
It seems to me that the discussion about whether and where in the train the loads are taken up begs the question of whether MU is really two trains coupled because railroads are required to have at least "one engineer" nominally in control of the entire train or for some other reason. It is correct that the current state of technology would easily facilitate one engineer controlling multiple separate trains from one locomotive. Coupling is not necessary for control any longer.
In the event of a required emergency stop, those "two trains" are going to be safer coupled together if they are as close together as you suggest.
Sheldon
The other thing that has to be considered is where the additional power is placed in the train, how many tons ahead and how many tons behind.
Yes there is constant adjustment of the tonnage being pulled/pushed as the train goes around curves, and up and down grades. Other than a bulk train (coal, oil, grain, ans, etc) the tonnage varies across the train, different length cars are loaded to different tonnages so the effects of grades, up and down, varies across the train.
Dave H. Painted side goes up. My website : wnbranch.com
LastspikemikeIs the dynamic behaviour of a MU hauled train mayerially different whether the locomotives are all at the head end or split mid train or even end train?
Yes. The purpose of distributing the power is to reduce drawbar forces. If you put all the power on the head end, all the tonnage is on the first drawbar. If you distribute the power, the total drawbar forces are lowered.
Second if you distribute the power you distribute the points from which a brake application are applied and released, that results in a quicker brake application, a shorter stopping distance and a quicker release means a quicker acceleration and both equate to improved fuel utilization.
Running multiple trains in close succession still is longer by teh disatnce between the trains. If you run a 15,000 ft DPU with 3 sets of power its 15,000 ft long. If you run 3 5,000 ft trains separated by 1000 ft, you now effectively have a train with a 17,000 ft footprint. Grade crossings are blocked longer, it takes longer to clear an opposing train, longer siding lengths are required, etc. Additional electronics are required to maintain the close separation.
And the benefits are......?
seems that consists and distributed power have been around since 1913 (at least on RDG)
do i see 3 consists in this picture
gregc seems that consists and distributed power have been around since 1913 (at least on RDG) do i see 3 consists in this picture
Some where packed away right now, and not available digitally, I have a series of pictures showing the Western Maryland moving about 75 hoppers out of one of their mine branches with two Consolidations on the head end, three Alco RS diesels in the middle, and two more Consolidations on the rear, about 1950.
Many of their mine branches had very sharp curves, steep grades, and lighter trackage that made larger power not suitable.
So seven locomotives, five crews, to move 75 hoppers about 70 miles - typically took all day. But two or three smaller trains would have actually required more than one day.
So all this talk about these fancy automatic controls these days is interesting, but not nearly as interesting as how those guys did this with a mix of steam and diesel all those years ago.
All thru the 40's and 50's steam and diesel was mixed for double heading, pushers and mid train helpers - and generally without radios either..........
Mike, that's all very interesting......... if you are interested. My comments on this thread have been limited, by one simple fact, I don't have much interest in current or future rail technologies.
So, since I'm really not interested, I will choose to leave you to it, and not invest any more thought into that part of the subject.
My interests lie in those Western Maryland mixed helpers I described, or in the B&O using diesel pushers on steam powered trains on Cranberry grade, and other similar grades.
As for self driving Teslas, that is way outside my interests.......
I was once well rounded until I learned what I really like........