DPU operating questions

[SD70Dude]

guetem1

I can only speak as a dispatcher, but on road trips I have had engineers demonstrate a "fence" that can be put up between lead and rear units, so you can have your lead units braking and the rear units still shoving as you take a train over a hill.  So braking can be different as well as throttle settings and of course dynamics between the lead and rear units.  On my RR we only dp front and rear but toward the west coast more mid-train DP's are used

I'm in a hurry right now, but will post some more detailed answers later today or tomorrow, if Jeff or someone else doesn't already.

On CN we call it the "fence" as well, which appears as a vertical line on the DP control menu screen.  You only have one fence, regardless of how many remote consists the train has.  I believe the DP system allows up to 4 remote consists but the most I have ever seen is 2, CN runs certain trains with both mid-train and tail-end remotes.  If you have such a train you can control the tail-end consist independently, or have the lead consist doing something different than what the two remotes are.

The technical term for using the fence is "independent motoring", when not using the fence you are in "synchronous mode".

In independent motoring you can have the remote(s) pushing in throttle with the lead in dynamics, but not the other way around.  I have always assumed the system will not allow you to put the remote into DB with the lead in throttle, but since our rules forbid handling the train in that manner I have never actually tried to see if it is possible.

[blue streak 1]

Around here CSX is placing DPU about 2/3 way back of IM trains.   Front end ( 2 units ) may be in any throttle posittion.  But 2/3 back full out pushing /pulling.  May have more to do with track is somewhat hog backed in places.   As far as manifest ? ? ?

[guetem1]

I can only speak as a dispatcher, but on road trips I have had engineers demonstrate a "fence" that can be put up between lead and rear units, so you can have your lead units braking and the rear units still shoving as you take a train over a hill.  So braking can be different as well as throttle settings and of course dynamics between the lead and rear units.  On my RR we only dp front and rear but toward the west coast more mid-train DP's are used

[zardoz]

I never had a chance to operate with DPU's, as they came into use just after I retired. So I have a few questions on how they are operated.

For my questions, let's assume a 150-car train of 2 engines up front, 2 mid-train, and 2 on the rear, trudging along at 25mph.

If the lead engines are pulling the first 50 cars, and the mid-trains are pushing 25 cars as well as pulling 25, and the rear units are pushing their 50, how is the slack beyond the range of the lead units controlled? Somewhere between car 1 and car 75 and also between car 76 and car 150 is there a point where at least one car is 'floating'--neither being pulled by the head-end power or being pushed by the engines behind it?

If that is the case, would the 'floating' car change positions as topography dictates, and if it does change position, how does the slack in the cars ahead and behind the changing 'floater' position behave?

Is all of this slack action visible in the various "add-on" control systems' displays?

 

Now let's change the train situation to one where the train is struggling up or down a grade at 5mph. 

Does the train still have slack issues similar to as described above? Are there places where there is neutral slack, or is everything bunched with no floaters?

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Some generalized DPU queries:

1. To what extent can the units be individually controlled?

2. With the lead unit working dynamics and the rear unit working power, what about mid-train units? Can they be configured per Engineer's request?

3. What locomotive functions are controllable from the lead unit? Is it similar to the 27-point jumper controllability?

4. If the second unit is connected via the 27-pointer, can that unit still be controlled by the DPU system?

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For those with "hands-on" experience:

1. Do you like using DPU's, or are they a pain?

2. As the Engineer, do you get to chose how the DPUs are configured?

3. Are some systems better than others?

4. How "interesting" does it get when in mid-trip the DPU suddenly stops working, either mechanically (stops loading) or electronically (stops communicating)?

5. How much information regarding the status of your DPUs do you get? Does each DPU have its own display screen that you need to scroll to, or is there one screen that summarizes all of your units?