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Different Locomotives Working Together

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Posted by SD70Dude on Saturday, November 21, 2020 8:11 AM

Lithonia Operator

Let's say that you had two units up front, a mid train engine, and a tail end unit. 2 x 1 x 1

The lead unit suffers a failure, requiring the prime mover to be shut down.

Can you still control the power from the lead unit?

Yes.  Until the batteries die.  

Lithonia Operator

If the lead unit is totally shot, so much so that it can't be used as a "cab car," is the enginee allowed to run from the second unit? If so, would it be required that the conductor ride the dead lead unit, as a lookout?

The rules may vary from railroad to railroad.  In my area a member of the crew must be positioned on the leading end to view signals when approaching them, or in non-main track when visibility is restricted from the controlling unit.  

Lithonia Operator

And if the second unit must be the controller, will this mean someone must walk to the the DP units, to reset something telling them to heed a different master?

Yes.  And if your new "leader" is facing backwards, you will have to re-qualify the remotes again after you wye the lead unit later in the trip.

It's a bit simpler on a conventional train, and some EOT's can be armed and tested from the lead unit, others require an employee to go back there and push the button a few times.  

Greetings from Alberta

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Posted by MMLDelete on Saturday, November 21, 2020 3:55 AM

Let's say that you had two units up front, a mid train engine, and a tail end unit. 2 x 1 x 1

The lead unit suffers a failure, requiring the prime mover to be shut down.

Can you still control the power from the lead unit?

If the lead unit is totally shot, so much so that it can't be used as a "cab car," is the enginee allowed to run from the second unit? If so, would it be required that the conductor ride the dead lead unit, as a lookout?

And if the second unit must be the controller, will this mean someone must walk to the the DP units, to reset something telling them to heed a different master?

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Posted by BaltACD on Friday, November 20, 2020 7:31 PM

Overmod
 
Paul Milenkovic
, all of the running locomotives supply brake line air pressure. 

You'll get a better picture if you think of each locomotive's air compressor charging that locomotive's main reservoir.  As SD70dude notes, all the main reservoirs in an MUed consist are piped together to act as one with higher volume, and you can  run multiple compressors to get larger volume into the reservoir system. 

This assists in charging the trainline in some respects, but not others; as noted, the trainline is charged only through the operating brake valve on each consist, NOT by all the compressor outputs delivering separately.  So the added effect is through less pressure drop from the main reservoir(s), not larger mass flow in parallel to charge the pipe through larger delivery area.

Despite the combined air pumping and reservoir capacity of the combined locomotive consist - the limiting factor in charging up the air brake system on a train is the amount of air that can be handled through the trainline, which has a internal diameter of apporximately 2 inches - 2 inches to charge all the reservoirs, both service and emergency on all the cars in the train.  The more cars, the more air must be pumped through that 2 inch diameter 'air highway'.

The difference between Main Reservoir Pressure (nominally 130-140 PSI) and train line Feed Valve setting (normally in the 90-110 PSI range) as well as the size of the Main Reservoirs when compared to car reservoirs is intended to keep a steady supply of air moving through the trainline when necessary.

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Posted by Overmod on Friday, November 20, 2020 6:03 PM

Paul Milenkovic
, all of the running locomotives supply brake line air pressure.

You'll get a better picture if you think of each locomotive's air compressor charging that locomotive's main reservoir.  As SD70dude notes, all the main reservoirs in an MUed consist are piped together to act as one with higher volume, and you can  run multiple compressors to get larger volume into the reservoir system.

This assists in charging the trainline in some respects, but not others; as noted, the trainline is charged only through the operating brake valve on each consist, NOT by all the compressor outputs delivering separately.  So the added effect is through less pressure drop from the main reservoir(s), not larger mass flow in parallel to charge the pipe through larger delivery area.

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Posted by SD70Dude on Friday, November 20, 2020 1:13 PM

The lead locomotive and the controlling unit in the remote consist will have their automatic brakes valves cut in, and are the only units directly supplying air to the train.  

Trailing units in each consist provide additional air to the lead unit through the main reservoir equalizing pipe (one of the three MU air hoses found on modern units).  This helps maintain the lead unit's MR air supply if it's compressor cannot keep up. 

Greetings from Alberta

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Posted by Paul Milenkovic on Friday, November 20, 2020 12:57 PM

According to a snarky remark in the last of the Kalmbach Diesel Spotter's Guides that I had seen, all of the running locomotives supply brake line air pressure.

Or at least the GE's do, until they shut themselves down.

If GM "killed the electric car", what am I doing standing next to an EV-1, a half a block from the WSOR tracks?
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Posted by JPS1 on Friday, November 20, 2020 10:17 AM

Here is a somewhat related question:  Yesterday I saw a coal train from my favorite train watching spot.  It appear to have about 120 to 160 cars.  I lost count. 

The train was led by two Dash-9 locomotives; two SD70 locomotives brought up the rear.  Which locomotives provide the air pressure for the train?  

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Posted by BaltACD on Thursday, November 19, 2020 7:26 AM

rdamon
Nice video of a MU separation.

https://youtu.be/6aF3LkCa2V0

There are shut off valves for each of the pneumatic hoses that are separating on each engine.  Part of the routine in separating locomotives in addition to disconnecting the 27 pin MU cable that distributes electrical controls among all engines in the consist is to turn all the valves for each of the pneumatic control hoses to the closed position on each of the locomotives at the separation point.

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Posted by rdamon on Thursday, November 19, 2020 6:23 AM

Nice video of a MU separation.

https://youtu.be/6aF3LkCa2V0

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Posted by BaltACD on Monday, October 26, 2020 4:25 PM

BigJim
 
BaltACD
they are dependent on the designated Lead locomotive to defined direction of movement to the Trail units by the electrical and pneumatic control signals that are sent from Leader to Trail units via the MU and pneumatic connections.  

There are no pneumatic control signals between the locomotives that pertain to which direction the units are travelling. 


They pertain to the controlled ability to stop among all the units of the engine consist so coupled.

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Posted by Overmod on Monday, October 26, 2020 2:46 PM

zugmann
MR, actuating, apply & release.

Thanks.

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Posted by zugmann on Monday, October 26, 2020 12:04 PM

Overmod
More precisely, the hose connections made when units are MUed pertain to 'control' over several functions of the air-brake system, including charging, main-reservoir equalization, and independent-brake connection between units.  (These multiple connections were seen on electric locomotives like GG1s, not just diesel-electrics.)

MR, actuating, apply & release. 

   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 Monday, October 26, 2020 11:37 AM

BigJim
There are no pneumatic control signals between the locomotives that pertain to which direction the units are travelling.

More precisely, the hose connections made when units are MUed pertain to 'control' over several functions of the air-brake system, including charging, main-reservoir equalization, and independent-brake connection between units.  (These multiple connections were seen on electric locomotives like GG1s, not just diesel-electrics.)

Naturally on locomotives with pneumatic throttles, there would be air connections.  There are very few of these still operating.  I don't know if there are two locomotives so equipped still running in MU ... perhaps on SMS?

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Posted by Jackflash on Monday, October 26, 2020 10:09 AM

The two control wires for forward and reverse are reveresed at the rear of the locomotive and in the MU cable, the are not reversed at the front of the locomotive.

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Posted by BigJim on Monday, October 26, 2020 8:47 AM

BaltACD
they are dependent on the designated Lead locomotive to defined direction of movement to the Trail units by the electrical and pneumatic control signals that are sent from Leader to Trail units via the MU and pneumatic connections. 


There are no pneumatic control signals between the locomotives that pertain to which direction the units are travelling.

.

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Posted by BaltACD on Monday, October 26, 2020 8:08 AM

Lithonia Operator
But how do the rear-facing units know that the lead unit's "Forward" is "Reverse" to them?

When set up in Trail - units have no idea what is ahead or back - they are dependent on the designated Lead locomotive to defined direction of movement to the Trail units by the electrical and pneumatic control signals that are sent from Leader to Trail units via the MU and pneumatic connections.  When set in Trail, locomotives cede their 'mind' to the Leader. 

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Posted by Overmod on Sunday, October 25, 2020 2:28 PM

Lithonia Operator
But how do the rear-facing units know that the lead unit's "Forward" is "Reverse" to them?

In 27-pin AAR MU it's handled through the cabling.  Remember that in all 'trailing' units the reverser handle has to be centered and the handle removed...

In DPU each trailing consist has to be set for direction at the unit containing the radio receiver but the other locomotives in that consist are 'automatically' cable MUed.

Recently I reviewed the GE 29-notch MU on the PRR E44s when participating in the thread containing the 1966 DDR proposal.  There the issue of 'handedness' was addressed by having MU receptacles both sides but keeping cables between units 'all to the same side'.

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Posted by SD70Dude on Sunday, October 25, 2020 2:27 PM

Lithonia Operator

But how do the rear-facing units know that the lead unit's "Forward" is "Reverse" to them?

It is hardwired in.  

I believe that the forward and reverse pins are in opposite places on the MU plugs at the front and rear of the locomotive.

When setting up DP the direction in relation to the lead consist must be entered manually, you can choose "same" or "opposite".  If you get it wrong the remote will work against the lead consist (this has happened a few times over the years).

Greetings from Alberta

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Posted by MMLDelete on Sunday, October 25, 2020 1:42 PM

But how do the rear-facing units know that the lead unit's "Forward" is "Reverse" to them?

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Posted by BaltACD on Sunday, October 25, 2020 1:02 PM

JPS1
This is a related question.  I think! 

Yesterday I saw three BNSF Dash-9s pulling a train past my next best train watching spot.  The first locomotive was facing forward, but the two trailing locomotives were facing rearward.  Or for the uninformed like me, the front locomotive was going forward and the two other locomotives were backing up. (Chuckles will be held to a minimum please.)

When the locomotives are positioned like so, do the ones that appear to be backing up have to be set manually before the train departs or is the process automatically set from the lead locomotive? 

Trailing locomotives, no matter the direction their cabs are facing, are set up as 'trailing' locomotives.  As such their electrical and power circuits are controlled by the control inputs that the designated 'lead' locomotive makes.

When the Engineer places the reverser in Forward and then advances the throttle to notch 4 - all locomotive that have been configured as 'TRAIL' will do the same.  The 27 pin MU cable that is connected between the units transfer all the electrical controls, the 'small' air hoses on either side of the coupler when coupled between the units pass all the pneumatic contol inputs.

When you start talking DPU - Jeffhergert would be the local expert.

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Posted by JPS1 on Sunday, October 25, 2020 11:23 AM

This is a related question.  I think! 

Yesterday I saw three BNSF Dash-9s pulling a train past my next best train watching spot.  The first locomotive was facing forward, but the two trailing locomotives were facing rearward.  Or for the uninformed like me, the front locomotive was going forward and the two other locomotives were backing up. (Chuckles will be held to a minimum please.)

When the locomotives are positioned like so, do the ones that appear to be backing up have to be set manually before the train departs or is the process automatically set from the lead locomotive? 

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Posted by Backshop on Monday, September 7, 2020 7:27 AM

blue streak 1

If my memory is correct...  The Atlanta and StAndrews Bay RR ( Bay line ) had an old Alcoa Road Switcher model unknown on display in Panama City, Fl.  Opened the MU cable connector and it only had about 19 (?) pins. That was a surprize to me.

 

RS1

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Posted by Overmod on Monday, September 7, 2020 7:24 AM

I think this is an older style of GE multiple-unit control; units up to S4 had it, which I think is long past the time of air throttle control on 539 Alcos.  I can't remember the date of adoption of AAR S-512, but I suspect the GE system (derived from electric practice, iirc) predates it.

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Posted by Erik_Mag on Sunday, September 6, 2020 5:51 PM

I suspect the Alco was old enough to use an air throttle, thus needing fewer MU connections.

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Posted by blue streak 1 on Sunday, September 6, 2020 5:05 PM

If my memory is correct...  The Atlanta and StAndrews Bay RR ( Bay line ) had an old Alcoa Road Switcher model unknown on display in Panama City, Fl.  Opened the MU cable connector and it only had about 19 (?) pins. That was a surprize to me.

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Posted by blue streak 1 on Sunday, September 6, 2020 5:00 PM

Darn duplicate postings.

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Posted by SD70Dude on Friday, September 4, 2020 4:55 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? 

Modern locomotives all use the same connections and are full interoperable.  Some older units (pre-1960s) had slightly different MU cable pin arrangments and not all the features would work on trailing units when you had mixed consists (NDG stated on several occasions that EMD and FM units had different dynamic brake control systems, and the DB would not work on trailing units when the two were coupled together). 

Air brakes are another story, some older units with 6 or 14 (and some 26) "one pipe" systems could not lead units with 24 (and most 26) "two pipe" systems, as there would be no way to bail off the trailing units.  Someone eventually realized that in this situation you could connect one of the lead unit's MU sander air hoses to the bail off hose on the trailing unit, and then turn the applicable sander switch on whenever you wanted to bail off. 

Most Baldwin diesels had a air-controlled throttle that was not compatible with units from other builders, though some were later retrofitted to make them compatible. 

Specialized features like Distributed Power and Pacesetter (automatic slow speed control) still have their quirks and surprises.  The latest versions of DP (since about 2015) seem to have resolved most of the compatibility issues, but I've seen a few cases where we couldn't get older units from different railroads to link to each other, and of course the older Locotrol I and II systems are not compatible with modern DP. 

Pacesetter seems to have been standardized since about 2005 (GEVO and SD70M-2/ACe), but anything older than that can have any one of several systems, and not all of them will work together.  With a mixed consist there was no way to know in advance exactly how each trailing unit would react to the leader.  Some would trail properly behind units they could not lead, some would trail in straight throttle, others would rev up and not load, or not react at all. 

Greetings from Alberta

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Posted by jeffhergert on Friday, September 4, 2020 4:54 PM

zugmann

 

 
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?

 

 

Those engines equipped have a consist monitor.  There's a limit to how many trailing units it will display, but all you see is tractive/brake effort.  At least you know if the trailing units are working.  I've had too many engines with smart start/stop that won't restart when needed and won't ring an alarm bell that there's a problem.

There was an EMS (Smart Consist) that showed what the trailing units (up to 2) were doing, but SC was deciding how each engine produced power.  No one, except maybe bean counters who don't know much about how things really work in the real world, liked it.  Even managers, except those who drowned in the kool-aid and thought they were destined to high management positions, who had to enforce it's use thought it was a big waste all the way around.

Jeff  

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Posted by jeffhergert on Friday, September 4, 2020 4:44 PM

SD70Dude

 

 
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.

 

For us, they've always known if you used the EMS or not.  Even if you logged in but ran manual, they knew it.  It's why at the end of the trip you had to give feedback as to why you didn't use it when it was available.

Jeff  

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