Could some one help me understand a little more about how DPU works? I understand the basics that 4 or more motors are in a consist controled by the lead locomotive. However is the entire load off cars streached when the move and if they are how does the rear power push when the train is streached or is this dynamiclly controled by the computers? (Rear given more power when needed or retarded when needed for example) Thanks for any information out there. S
Welcome aboard, Steve, DPU's (Distributed power Units) are the units in the middle or back of the train. They are controlled by radio from the head end and generally respond the same as if they were part of the head end consist. The locomotives in the head end consist are not DPU's, but rather connected by a system called Multiple Unit operations or MU. THe difference is that MU units are controlled by a wired system and DPU's are controlled by radio. The latest products from EMD have a system called CTE for Controlled Tractive Effort specifically to manage the DPU's and reduse derailments from having the helpers push too hard. Hope this helps.
Yes kind of figured that there had to be something keeping the helpers cause problems. My rail road hobby led me to ask this question as I have this problem on a tiny scale so I made sence that in prtotypical operation this could be an issue. Thanks
The DPU's are controlled from the lead locomotive. On the UP, we use a Harris box, made by Harris Industries, IIRC. The neat feature about DPU's is you can run the remote locomotives in power while the lead units are in dynamic, or visa versa. Also, you can run both DPU and controlling consists in the same mode. DPU's aren't fail safe, but a lot of tonnage has been moved over the last few years and they are proving to be reliable. GE is putting out the CTE, not EMD. EMD may have their own version out. The CTE has been used on the AC locomotives.
I saw an interesting BNSF train about a month ago in Vancouver Wa. about 3/4 of the way back were DPU engines. I couldn't figure out what was so special about that 3/4 mark. why not the half way mark? or the end of the train? Plus it was one of the longest trains I've ever seen, it was heading east onto former SP&S trackage and I'd be surprised if it could fit on the sidings. Any ideas on why they cut the power in there? My only thought is that maybe the train was splitting up at Spokane or someplace relativly close so they ran one train and then the DPU units would be another train.
It has to do with train make up. Some times it is easier to put them ¾ of the way in the train rather than on the rear with enough loads to shove against. When SP ran trains with manned helpers, they would often put a set 2/3’s or ¾’s of the way back. That way they could keep their cars blocked with out regard to where the loads and empties are in the train. In Sparks, we reblock trains all the time to make sure there are enough loads on the rear to shove against. As for the train being too long to meet at any sidings, they will do that and everything else will have to go into the hole to meet them. Greg Elems
Thanks everyone for the great information. It really helps fill the gaps on how it works. I had not even thought about haveing front power in Dynamic and the rear still pushing but it makes sence. Steve
