via E-Mail
This month's feature will be addressing Distributed Power operations. The first item will focus on a question from an engineer in Coffeyville, Kansas. Ther will also be other DPU data of various natures which, from both the railroader and railbuff points of interest, you may find worthwhile.
The Questions Situation: To the inquirer, it appeared to take a long time for the air brakes to set up on the train. On the control box console, there wasn't a reflection of the remote unit mirroring the actions of the lead consist (At the time, he was working in the Synchronous mode arrangement). Moments after receiving a response from the remote, the train air went into emergency. Prior to this, the inbound engineer informed him that the brake pipe did not contain a "short fuse".
Question: What are the whys behind this sequence of events?
The Answers
Because the inquirer was dealing with a couple of ingredients, let's now break down what put this together.
The Time Lag Readout:
This circumstance is normal. From the lead consist, you are sending out first a command via the brake pipe to the remote consist(s). The remote unit(s) then send out an air brake signal via the radio. So even though the transaction you started actually took place sooner, it only seems like teh status update from the remotes is returning to you several seconds later.
The "Short Fuse":
The cause for this very likely was due to a car control valve at that moment having enough sensitivity to kick over into emergency, resulting in transmission of the emergency throughout the train. Now yes, when initial operations of DPU began the use of remote consist(s) leaders outfitted with E-Brake systems, the BCC (Brake Control Computer) was misreading an initial brake pipe reduction as a signal to go into emergency.
This condition has since been corrected by way of software upgrades to the E-Brake system. ABTH Rules 31.5.6 & 31.9.2A, part 1: Their Effects on DPU Trains
Now let's examine what to expect whenever DPU trains experience an emergency brake application. First - How does Rule 31.5.6 (Continuous Dynamic Braking) have an effect? Dynamic braking will be retained on all consists in the train, regardless of the source of the emergency.
The application of Rule 31.9.2A, part 1 (The 20 Second Power Throttle Delayed Knockdown) has various plot twists which determine whether or not the feature becomes active (So as to not throw you off: All UP and CNW units equipped for DPU are power throttle delay KD equipped). If the train incurs a trainlined emergency initiation, all consists should kick into effect the 20 second delay feature. However, if it is a remote consist that is first to pick up the emergency signal, power throttle knockout will be immediate.
Other factors:
If the source of the emergency signal is by the Remote Control Emergency (radio signal) feature, or by some other source (such as a crew induced emergency from the lead consist), power throttle knockdown will occur immediately.
Another Personal DPU Encounter:
Here is some troubleshooting material I wpold like to pass alongfrom one of my tours of work; the job was DPU empty coal train CHPJR-18.
A number of times during the trip, the remote unit kept giving off Alarm screen messages of Mode Idle and Mode Invalid.
If the remote unit was producing output when the situation cropped up, the remote would drop out to Idle. These messages mean that there is a mode discrepancy between the lead consist and the affected remote remote consist (Translation: The throttle positions, while operating the train in the Synchronous mode, are not matching up).
A tactic you can attempt to offset this is to set up the DPU system into Front/Back groups to see if the remote unit might begin to respond properly while in the Back group control setup.
FYI: The next time you climb aboard a DPU equipped C44AC locomotive of the SP, you might find this sticker posted in the cab:
"UPRR DPU SOFTWARE EQUIPPED - WILL NOT LINK TO SPRR SOFTWARE EQUIPPED UNITS".
Such locomotives are carrying this as a temporary measure; the shops performing this work are Denver and North Platte.
A by-product of this alteration is the inaccurate display of amperage instead of Klbs output on the control box console out of the SP unit (This condition will be corrected).
Railbuffs Data:
Yes, there have taken place operations of DPU coal trains into Texas which has a modified SP unit linked up to a UP unit.
Other DPU News for Railbuffs: February 2, 1998: Train CBTHS-30 featured as DPU linked locomotives a pair of CNW C44AC's
It Did Occur... In A Round About Way: Well, I finally did get to trace down an event I wrote about wanting to see which transpired after last month's issue; the first run of an SPRB to South Texas DPU coal train which featured as the power all SD90/43MAC locomotives.
The job was the CCDSA-07; it arrived in Fort Worth on March 10th with 128 loads, 16658 tons.
What made this an historic event for our area? It had four units in the lead consist and one unit in the remote position. Four of the locomotives were SD90/43MAC's. The unit numbers:
The other all SD90/43MAC DPU Texas bound coal train was the CBTHS-11; arriving into North Platte on March 14th, it had 128 cars being worked by this trio:
A Look Ahead:
My Closing Observation: