DPU used more often now? photo included...

Trains Magazine General Discussion
1

Recently through MN I’ve seen a lot more DPU’s on the rear of heavy trains. Heavy trains have always gone through here in the past, but usually with a lot of head end power. Is DPU catching on even more with railroads? What are the rail crews on the forum seeing?

I know some of the advantages are fuel economy and added train length are there others?

Here’s one example: BNSF 4040 shoving on the rear of grain loads.

2

CP has always been a big user of DPUs.

Out in my area it’s completely common to see all kinds of CP trains with a single unit on the front and a single unit on the back.

I know it’s often a little more of a pain to get a DPU set-up because you have to get a Unit popped onto the tail end, instead of just tacking onto the head end and chugging away.

DPUs are nice though, because they really assist in limiting the train forces, makes for a smoother ride.

3

All five of the Western Class Is (I’m including CN and CPR in that) adopted DPU almost at the same time, as I recall. As they obtain more units that are DPU capable, and have more experience with it, they continue to expand its use. DPU hasn’t caught on in the slightest on the two eastern roads, and I don’t think it will – their geography and traffic is much different and I doubt DPU would help them as much. However, they have DPU runthroughs on Powder River Basin coal trains, such as to Georgia and Alabama, interchanged from both BNSF and UP.

Other major advantages:

  1. lower buff forces, allowing fewer tonnage restrictions on descending grades and into controlled sidings.
  2. the remote unit can charge the train line, which essentially eliminates the use of retainers, gives faster recharge times, avoids a lot of cold-temperature problems
  3. less brakeshoe wear, less wheel wear
  4. lower lateral and longitudinal forces on track, which lengthens tie life and reduces alignment problems
  5. fewer broken drawbars, meaning fewer train delays and recrews
  6. manned helper operations abolished, a major savings in labor
  7. can act as its own Fred, so one less thing to break, get loss, be in short supply
  8. most of all: MORE TONNAGE for the same crew, so more productivity.

Disadvantages:

  1. lot of time wasted in terminals and at origins and destinations cutting them in and out, reducing cycle time
  2. a significant gain in locomotive miles per train miles
  3. some train-handling problems with inexperienced crews

OS

4

Also, metal that is cyclically loaded has a stress-cycle curve. The lower the stress, the more cycles until failure. Most steels, if the stress is low enough can have a practically infinite life (in terms of the stress-cycle curve), although I doubt the stress in the knuckles is this low.

5

Most of the coals here have one 2 on the head, 1 on the rear. Some have 3 on the head.

6

To quote from the movie "Master and Commander “Another marvel in this wonderous age in which we live.”