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multiple DPU's

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Posted by kgbw49 on Sunday, July 24, 2022 4:31 PM

BaltACD and jeffhergert, thank you so much for sharing that knowledge! Much appreciated!

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Posted by jeffhergert on Sunday, July 24, 2022 2:10 PM

The number of engines on the head end is often misleading.  At best, you could have 4 of the engines on line due to powered axle limitations in that picture. 

I would be surprised to see that many on line.  With fuel conservation rules, it wouldn't surprise me if only the lead engine was on line with a mid train DP, or a mid train and rear DP working. 

Jeff

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Posted by BaltACD on Sunday, July 24, 2022 11:48 AM

kgbw49
Layperson question - would a train with this much horsepower on the front end likely have a DPU on the rear? I can't tell from the picture because it looks like the end of the train is out of sight on the bridge approach across the river. Thank you!

https://www.railpictures.net/photo/808234/

don't know UP's train handling rules.  It is highly likely that no more than three of the head end units are on line an under power.  I don't know what sort of rules UP applies to the use of DPU units within or behind a train.

Modern AC units when operated in MU control have the potential to be asked to haul more train than the design strength of knuckles can withstand.  In theory the power could break a knuckle on a sustained pull.  Note: most broken knuckles happen because of a 'train handling hiccup' which results in instantaneous maximum buff and draft forces being applied to the knuckle.

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Posted by kgbw49 on Sunday, July 24, 2022 10:55 AM

Layperson question - would a train with this much horsepower on the front end likely have a DPU on the rear? I can't tell from the picture because it looks like the end of the train is out of sight on the bridge approach across the river. Thank you!

https://www.railpictures.net/photo/808234/

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Posted by jeffhergert on Wednesday, July 20, 2022 6:45 PM

Jackflash

Jeff,  Do you remember the Harris boxes?  Well there was a way to "fool" it to let you put the rear DPU into DB and still pull the train from the head end, in order to "streach" it out.  Came in handy at times.

 

I never heard that about those boxes.  We were talking about them the other day.  It seems there's a locker full of them at one of our outlaying terminal that handles a lot of grain train power.

Today's train handling seems to be albout having the slack shoved in all the time.  Even when many trains are better stretched out.

Jeff 

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Posted by Jackflash on Wednesday, July 20, 2022 5:21 PM

Jeff,  Do you remember the Harris boxes?  Well there was a way to "fool" it to let you put the rear DPU into DB and still pull the train from the head end, in order to "streach" it out.  Came in handy at times.

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Posted by jeffhergert on Wednesday, July 20, 2022 2:58 PM

BaltACD

 

 
jeffhergert
Yes the fence can be put up, taken down. or moved as the engineer desires.  Our rules changed awhile back so the fence always has to be up.  The system instruction says the fence can be anywhere, but local instructions in some areas can specify where it's put. 

EMS auto throttle when engaged can do what it wants anywhere, no matter other instructions.  on a three consist train, EMS will put the fence between A and B.

Before the requirement, I would use the fence a lot on certain trains at certain locations.  I don't agree that it's necessary on some trains to use the fence at all times.  Like so many other things, it's knee-jerk reaction to problems trying to keep over sized trains in one piece, developed by people who only have run these trains on the simulator.

Jeff 

 

So UP rules now require the Fence to be up a all times?  Does this also apply when there are only two locomotive consists in the train - the leader and the DPU.

 

Yes.

Jeff

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Posted by BaltACD on Wednesday, July 20, 2022 11:46 AM

jeffhergert
Yes the fence can be put up, taken down. or moved as the engineer desires.  Our rules changed awhile back so the fence always has to be up.  The system instruction says the fence can be anywhere, but local instructions in some areas can specify where it's put. 

EMS auto throttle when engaged can do what it wants anywhere, no matter other instructions.  on a three consist train, EMS will put the fence between A and B.

Before the requirement, I would use the fence a lot on certain trains at certain locations.  I don't agree that it's necessary on some trains to use the fence at all times.  Like so many other things, it's knee-jerk reaction to problems trying to keep over sized trains in one piece, developed by people who only have run these trains on the simulator.

Jeff 

So UP rules now require the Fence to be up a all times?  Does this also apply when there are only two locomotive consists in the train - the leader and the DPU.

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Posted by jeffhergert on Wednesday, July 20, 2022 11:30 AM

Yes the fence can be put up, taken down. or moved as the engineer desires.  Our rules changed awhile back so the fence always has to be up.  The system instruction says the fence can be anywhere, but local instructions in some areas can specify where it's put. 

EMS auto throttle when engaged can do what it wants anywhere, no matter other instructions.  on a three consist train, EMS will put the fence between A and B.

Before the requirement, I would use the fence a lot on certain trains at certain locations.  I don't agree that it's necessary on some trains to use the fence at all times.  Like so many other things, it's knee-jerk reaction to problems trying to keep over sized trains in one piece, developed by people who only have run these trains on the simulator.

Jeff 

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Posted by BaltACD on Wednesday, July 20, 2022 7:39 AM

jeffhergert
 
timz

If "multiple DPUs" means two sets of DPU units, one midtrain and one on the rear, what's the answer then? Throttle and brake settings have to be the same on the two sets? 

You only get one fence.  It can be placed between any two consists.  When you have two or more remote consists, two consists are going to have to be together.

You can have all 3 sets (A B & C) operate following commands from A, synchronous operation, A-B-C.  You can place the fence between A and B, in which case B and C will operate with the same settings, A/B-C.  You can place the fence between B and C.  B will mimic lead A's commands, while C is independently operated, A-B/C.

As to remote sets in independent mode being in dynamics while the lead is in power, that's not supposed to be possible in normal operation.  The danger is pulling the train apart.  I've only known it to happen when the remotes have lost communication with the lead unit.

Jeff

Am I correct that the 'Fence' setting can be changed by the Engineer as he sees fit for the safe and successful operation of his train.  ie.  Starts out with, say, No fence between A,B & C.  Down the road the fence needs to be between A and BC, later on the configuration needs to be AB and C fenced and later still A, B & C with no fence.

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Posted by jeffhergert on Wednesday, July 20, 2022 4:43 AM

timz

If "multiple DPUs" means two sets of DPU units, one midtrain and one on the rear, what's the answer then? Throttle and brake settings have to be the same on the two sets?

 

You only get one fence.  It can be placed between any two consists.  When you have two or more remote consists, two consists are going to have to be together.

You can have all 3 sets (A B & C) operate following commands from A, synchronous operation, A-B-C.  You can place the fence between A and B, in which case B and C will operate with the same settings, A/B-C.  You can place the fence between B and C.  B will mimic lead A's commands, while C is independently operated, A-B/C.

As to remote sets in independent mode being in dynamics while the lead is in power, that's not supposed to be possible in normal operation.  The danger is pulling the train apart.  I've only known it to happen when the remotes have lost communication with the lead unit.

Jeff

 

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Posted by blue streak 1 on Tuesday, July 19, 2022 11:40 AM

Around here the CSX  DPU operation is fairly simple. Almost always when there is a DPU it is about 1/3  way from front. CSX around here almmost always puts up the fence.   The DPUs are in run 8 or max dynamic.  The front loco adjusts its power for whatever speed is needed.  Guess engineers might liike the less prime mover diesel roar. 

I have noticed a version of power braking..  The DPU will be in max dynamic as the front loco will use a littlepower to a stop.

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Posted by mvlandsw on Sunday, July 17, 2022 1:28 PM

timz

"If "multiple DPUs" means two sets of DPU units, one midtrain and one on the rear, what's the answer then? Throttle and brake settings have to be the same on the two sets?"

What about this situation? If there are more than one DPU, can each one be controlled separately by "putting up the fence" or do all DPU's follow the same commands?

 

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Posted by Overmod on Sunday, July 17, 2022 8:04 AM

dbduck
I guess I didn't make myself clear or use the right terminology.

what I'm asking...if there is 1 set of two locomotives,one behind the other in the middle of a train, does each of those locomotives receive commands from the head end or does only one receive the commands and the second locomotive MUed to it "normally " and follow

I kept trying to edit my original answer to clarify this and just kept failing miserably.

If you have two locomotives coupled together in the middle of a train, only one of them is operating under DPU radio control.  The others are in MU and respond just as they would to 'human' throttle and DB control.  It is the latter of the two alternatives you gave.

As Jeff noted, you can isolate unit(s) in a group of two or more locomotives and still have the others respond to the DP-originated commands.

The signal actually sent to distributed power consists does NOT have to be just a 'repeatering' of what the engineer is doing moment-to-moment with the throttle or dynamic.

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Posted by jeffhergert on Sunday, July 17, 2022 3:35 AM

The individual consists have one linked controlling unit.  It doesn't have to be any specific one when in the consist, it just needs to be equipped.  The other engines in the consist don't necessarily have to be on-line, or even running.  That depends on the locomotive requirements for the train.

The DP screen only show data from the linked controlling remote. You may not know if other engines in the DP consist are working or not.  Some of the newer ones will give consist totals for tractive and dynamic braking effort, if the individual engines are equipped to share that information.

Jeff

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Posted by YoHo1975 on Friday, July 15, 2022 2:56 PM

One has DPU enabled and the other is mu'd to the first. You see on UP all the time that mid train DPU has a known DPU unit and some number of non-dpu units (like the SD70Ms) with it.

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Posted by dbduck on Friday, July 15, 2022 2:53 PM

timz

If "multiple DPUs" means two sets of DPU units, one midtrain and one on the rear, what's the answer then? Throttle and brake settings have to be the same on the two sets?

 

I guess I didn't make myself clear or use the right Termanology.

what I'm asking...if there is 1 set of two locomotives,one behind the other in the middle of a train, does each of those locomotives receive commands from the head end or does only one receive the commands and the second locomotive MUed to it "normally " and follow 

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Posted by timz on Friday, July 15, 2022 11:12 AM

If "multiple DPUs" means two sets of DPU units, one midtrain and one on the rear, what's the answer then? Throttle and brake settings have to be the same on the two sets?

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Posted by SD70Dude on Friday, July 15, 2022 9:10 AM

dbduck

are they MUed in "normal " fashion & the signal sent to only one of the linked units?

This.  Which also means that trailing units in a remote consist do not need to have DP equipment.

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Posted by Overmod on Friday, July 15, 2022 8:58 AM

I have never seen or heard of more than one radio in use per power consist, with the non-radio locomotives MUed to the one that has it.  There are a number of technical reasons for this to be 'preferred'.

That means one radio for each group of locomotives, whether trailing power or grouped in mid train.  Think of the system as sending the engineer's control settings to other locomotives.  You only need one engineer on a MUed consist, therefore you need only one radio-control unit on a MUed sep of DP

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multiple DPU's
Posted by dbduck on Friday, July 15, 2022 7:29 AM

If this has been asked before I apologize in advance

When a train has multiple DPUs lashed together either mid train or at rear, is each DPU individually controlled from the head end, or are they MUed in 
"normal " fashion & the signal sent to only one of the linked units?

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