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Different Locomotives Working Together

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Posted by SD70Dude on Friday, September 4, 2020 4:38 PM

zugmann
Overmod
My guess is that your actual control over much of that is limited by the interface in the first place, and by access permissions and 'not being distracted by electronics while maintaining vigilance (or some other mealymouthed excuse) should you try making informed use of the dataflow and controls.

If you only knew at times...

Here's an example. 

We used to be told to use Trip Optimizer as much as possible (CN doesn't use any of the other systems), and WiTronix would 'phone home' if we were not using it.  When in Trip Op we are exempt from obeying throttle restrictions, as the program is supposed to be smart enough to calculate how to save the most fuel. 

Eventually someone figured out that if you opened the Trip Op screen and "intialized" it, no alarms would be generated.  But you would still be free to manually control the throttle, without being hindered by those pesky throttle restrictions. 

Eventually the Company figured out what was going on, and now we are told not to use Trip Op, and obey the throttle restrictions religiously.

Greetings from Alberta

-an Articulate Malcontent

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Posted by Overmod on Friday, September 4, 2020 1:47 PM

zugmann
If you only knew at times...

Oh, I'd be delighted to know.  The contemporary equivalents of matches and flare sticks and a few pennies on the governor and extra transition relays and stuff in the grip are probably inspired and wonderful, particularly if "someone" were to learn the software equivalent of Gramercy Park keys and pass the word along...

Not that I officially know anything of the kind, of course, or leave any back doors or stuff open after, well, you know, someone spills the beans too much not to notice.  Heaven forbid.

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Posted by zugmann on Friday, September 4, 2020 1:26 PM

Overmod
My guess is that your actual control over much of that is limited by the interface in the first place, and by access permissions and 'not being distracted by electronics while maintaining vigilance (or some other mealymouthed excuse) should you try making informed use of the dataflow and controls.

If you only knew at times...

   The opinions expressed here represent my own and not those of my employer or any other railroad, company, or person.

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Posted by Overmod on Friday, September 4, 2020 1:22 PM

zugmann
Don't some of the newer engines have that smart consisting or EM stuff, and do know what the other engines are doing?

They do, and more is coming.

The point is that most of that stuff is also handled between computers, or communication via the 'back office', not directly meant to be manipulated  by the people, or person, or occasional flying 'superconductor' or riding supervisor when autonomous trains set in.  My guess is that your actual control over much of that is limited by the interface in the first place, and by access permissions and 'not being distracted by electronics while maintaining vigilance' (or some other mealymouthed excuse) should you try making informed use of the dataflow and controls.

Of course in an emergency it would be of great use to be able to reach out, diagnose, and develop workarounds for failing units you need...

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Posted by zugmann on Friday, September 4, 2020 1:09 PM

BaltACD
The volts and amps of each engine have no idea of the volts and amps of any of the other engines in the consist - each locomotive is working to its own maximum capability for the throttle notch that the engineer has selected.

Don't some of the newer engines have that smart consisting or EM stuff, and do know what the other engines are doing?    I know when I ran some of the GEVOs or ACes, I beleive they had displays that showed what other engines were doing, if they also had compatible software.  It's been a few years since I've had that high tech stuff. 

Jeff?

 

   The opinions expressed here represent my own and not those of my employer or any other railroad, company, or person.

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Posted by daveklepper on Friday, September 4, 2020 3:27 AM

And the resultant speed up the grade or acceleration results from their combined tractive effort and horsepower with the division not necesarily proportional to the different rated tractive efforts and horsepowers.

(Only if wheel sizes and gear ratios are the same, then possibly proportional depending on governor settings and contorl system timings)

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Posted by BaltACD on Thursday, September 3, 2020 6:59 PM

BigJim
 
JPS1
Yesterday I saw two Dash 9s and a SD40-2 pulling a freight train past my favorite train watching spot.  What issues, if any, arise when locomotives from different manufacturers operate together?  

In this case, absolutely none! These units don't know who made the one ahead or behind.

The volts and amps of each engine have no idea of the volts and amps of any of the other engines in the consist - each locomotive is working to its own maximum capability for the throttle notch that the engineer has selected.

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Posted by BigJim on Thursday, September 3, 2020 5:52 PM

JPS1
Yesterday I saw two Dash 9s and a SD40-2 pulling a freight train past my favorite train watching spot.  What issues, if any, arise when locomotives from different manufacturers operate together? 
 

In this case, absolutely none! These units don't know who made the one ahead or behind.

.

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Posted by Overmod on Thursday, September 3, 2020 4:55 PM

I start with some assumptions: steady-state, no unit either in traction-motor slow-speed or overspeed risk, etc.

As noted in some detail over on MR, the MU systems need to be compatible, and to a lesser extent the gear ratios should not be wildly disparate (not so much because they 'want to go at different speeds' as because the horsepower in MU-commanded notch may not produce comparable TE).  To an extent the speed with which locomotives load or unload affects their behavior in a consist: faster-loading ones may jostle their lazier neighbors (as has been remarked on both here and in Trains Magazine.

Sometimes the question arises 'how do the engines "know" which ones pull which share of the load'.  (Also 'why does it always look like one of two steam locomotives doubleheading always look like it's doing more of the work -- and is this true for diesel-electrics?')

Think of it by starting this way:  The rear unit has the entire consist's resistance pulling on its rear coupler.  There is usually no way in Hades that unit alone could pull that ... let alone push a unit ahead of it too.  The second unit forward, therefore, has at its coupler the full consist resistance (now including the mass of the trailing locomotive) LESS whatever that locomotive, running in commanded notch with corresponding excitation, is providing in wheel rim torque/dbhp to LESSEN the resistance.  And so forth up to the lead unit.

Now, the unit controls don't make this calculation (although if they had strain gages on the drawbars and the right computer or PLC installation, they could).  Instead their load regulators adjust excitation to keep the engines at constant rpm, which is separately adjusted with variable fuel.  Fairly rapidly this equilibrates the load among the units so that no one of them is running at 'full gate' trying to pick up more than its share, and I believe this will be true even if its 'share' is numerically higher or lower than its neighbors (e.g. a DD35 sandwich)

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Different Locomotives Working Together
Posted by JPS1 on Thursday, September 3, 2020 2:47 PM
Yesterday I saw two Dash 9s and a SD40-2 pulling a freight train past my favorite train watching spot.  What issues, if any, arise when locomotives from different manufacturers operate together? 

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